Spoke too soon! Car running like crap all of a sudden

[jawn101]

So the regulars saw my last thread on the subject of why my car was running so amazingly well earlier in the month. Well, the DeLorean curse came back around to bite me in the ass on that one...

I've been trying to get in a half hour of driving every evening while it's still nice out so I can get the fuel levels down (and enjoy the car, of course) to make it a little easier to pull my pump and inspect it, the tank and the hoses later in the season. Everything has been fine up until yesterday. I went out and felt like there wasn't really much power at all. There was a rich fuel smell, but the idle seemed ok. I made it about a mile from home and the engine was acting starved - could not tell if it was fuel or spark so I limped home with the flashers on. By then it was dark so I left it until this afternoon. It's still doing it, so I pulled all the plugs and injectors for a quick visual. Everything looked OK. Then I noticed that the frequency valve wasn't buzzing. Odd. I checked fuses #1 and #7 and they are OK. I pulled the RPM relay (I have Dave's solid state one) and jumpered the connector. I heard the Lambda relay kick on but the FV did not start buzzing.

So then I put a DVM across the plug to the FV and jumpered the RPM relay. 10.87v.

Bad FV? I've never heard of that. Is that voltage too low for some reason? Is that a symptom of a bigger problem, the cause of the dead FV, or is it normal?

[jawn101]

Forgot to mention that nothing's been knowingly changed between when the car was great and when it was suddenly running weird. I know the FV could be buzzing but at a very low cycle so it becomes difficult to hear/feel - but I haven't done anything to adjust the mixture. At least not deliberately?

[jawn101]

Reading over other related threads I'm growing less certain of what's going on here. I don't know if the FV would cause the stumbling and complete lack of power I was feeling on the road. Anyone have any thoughts on where to look next?

[Nicholas R]

How old is your O2 sensor? Sounds like a mixture issue. You could always unplug the O2 sensor and adjust the mixture manually to see if you can get it running right without the lambda systems assistance. Heck I ran open loop the entire time I had the PRV. I much preferred the mixture control.

[jawn101]

How old is your O2 sensor? Sounds like a mixture issue. You could always unplug the O2 sensor and adjust the mixture manually to see if you can get it running right without the lambda systems assistance. Heck I ran open loop the entire time I had the PRV. I much preferred the mixture control.

To my knowledge the O2 sensor is pretty new. I believe it was replaced just before I got the car in April of 2011 to help it pass smog. They didn't reset the counter though so I really don't know. It looks mighty new, shiny metal and bright white plastic. The mixture was spot on before this happened, but I'll check the wire to the sensor and see if there's something obvious. I don't know that I'm equipped to do the sensor myself though, given all the horror stories I've heard about them seizing and such. Maybe since it's relatively new it will come out easy.

Could that account for the stumbling and total lack of power?

[Rich]

.....Anyone have any thoughts on where to look next?

For what it's worth there's the factory manual for troubleshooting. This one is K-Jet-centric, does not cover blocked exhaust or ratty ignition.

http://dmctalk.org/showthread.php?3143-Factory-Engine-Diagnostic-Chart

That plus the old standby advice to try a shop that's wise to the ways of K-Jet and related parts as found on millions of other imported cars back in the day.


Hope you find the culprit soon, Jon.

[jawn101]

Thanks Rich. I'll go over a bunch of this stuff tomorrow. I just don't know what could have suddenly gone so wrong just sitting for a week. I don't have any way of checking fuel pressure but maybe I'll have to invest in a test kit.

[Ryan King]

Could that account for the stumbling and total lack of power?

My car JUST did this a few months ago. Its your fuel pump man. Check to make sure the pump is priming when you turn the key to the on position. My car was running just fine, daily driver, and it started gasping for fuel, i had to limp it home just like you. Bad pump. Pull the pump and inspect it.

*Edit* Even after pulling my pump and testing it, it still ran for a while but stopped again. I have since replaced the pump and my car has been just fine. Before you do any other work pull the pump

[Nicholas R]

I had an issue very similar to this when I had a PRV; stumbling, no power. Ended up being the ignition coil of all things.

Unfortunately that's the problem with what you're describing. There are a dozen different things that could describe what you're talking about.

[Bitsyncmaster]

When your engine is cold, the FV should be buzzing loudly running a 50% duty cycle. Has nothing to do with the O2 sensor until the engine has warmed up. Check that the FV gets battery voltage on one wire and the other wire is switching so a meter will read about 6 volts DC or 12 volts AC. The common problem is someone sticks the wrong relay into the "Main Fuel Relay". I wired mine to use the standard type relay.

[jawn101]

My car JUST did this a few months ago. Its your fuel pump man. Check to make sure the pump is priming when you turn the key to the on position. My car was running just fine, daily driver, and it started gasping for fuel, i had to limp it home just like you. Bad pump. Pull the pump and inspect it.

*Edit* Even after pulling my pump and testing it, it still ran for a while but stopped again. I have since replaced the pump and my car has been just fine. Before you do any other work pull the pump

Thanks Ryan. My plan all along has been to check out the pump, but not because there was anything wrong - just because I haven't done it yet and it's about the last thing I haven't replaced. It does prime at key on, key off, and when the pedal is depressed a few times with the car on but motor off, all behavior orchestrated by Dave's RPM module. I did have the pickup hose collapse on me last summer in extreme heat and the feeling was similar, but that happened at highway speeds which I can't even attain in the current state of things, so I'm not sure if it feels exactly the same.


I had an issue very similar to this when I had a PRV; stumbling, no power. Ended up being the ignition coil of all things.

Unfortunately that's the problem with what you're describing. There are a dozen different things that could describe what you're talking about.

Yeah, I know. Boo. I didn't think of checking the coil connection, which I will do for sure when I get home tonight. The coil is a new one from Hervey - a 40kV Pertronix that has been working just fine. I still have the original Bosch on the shelf and can try it out as it was fine when I pulled it. The thing I'm not sure about is how/whether a coil connection or a spark problem would result in the FV not buzzing.


When your engine is cold, the FV should be buzzing loudly running a 50% duty cycle. Has nothing to do with the O2 sensor until the engine has warmed up. Check that the FV gets battery voltage on one wire and the other wire is switching so a meter will read about 6 volts DC or 12 volts AC. The common problem is someone sticks the wrong relay into the "Main Fuel Relay". I wired mine to use the standard type relay.

Yep, and it always did before. I will check the voltages this afternoon as well - was measuring the two pins on the white FV plug as + and - on the DVM incorrect? Does that valve get ground somewhere else? I assumed it was correct because it was -10.87v until I switched the probes and it was then 10.87. The Lambda relay is the correct module and has not been changed/moved/altered at all.

[Bitsyncmaster]

Use the engine for ground and measure one wire at a time. The lambda ECU provides the ground with that 50% duty cycle on one wire and "fuel relay" provides the +12 volts with the engine running.

[jawn101]

Use the engine for ground and measure one wire at a time. The lambda ECU provides the ground with that 50% duty cycle on one wire and "fuel relay" provides the +12 volts with the engine running.

Ok, just did this. On the white FV plug, with the RPM relay removed and jumpered: Red/Brown to ground is a solid 12v. Red/Purple to ground sits at 0.30v with no detectable fluctuation on my DVM.

[Bitsyncmaster]

Red/purple should be the one that gets +12 volts from the fuel relay. Is your fuel relay the low height OEM relay?

You need to find out why the red/purple wire has no power with engine running or the RPM relay jumpered from the brown wire to the double yellow/red wires.

[jawn101]

Red/purple should be the one that gets +12 volts from the fuel relay. Is your fuel relay the low height OEM relay?

You need to find out why the red/purple wire has no power with engine running or the RPM relay jumpered from the brown wire to the double yellow/red wires.

I have Tyco relays from Hervey. Like I said, it's been working well for a long time. I hear and feel the relay engage when I jumper the RPM relay but the FV doesn't activate. I don't know why the wires would be reversed as nothing has been changed in this harness. I see on the schematic that R/P comes right from the lambda relay and R/N comes from the ECU. So logically the R/P would be always on and the R/N be modulated by the computer? Not sure why mine is backwards. Any idea where to start? I cleaned the lambda relay socket and lambda computer connector just now with no change.

[Bitsyncmaster]

You can swap the wires in the bulk head connector but if it was all working with that wiring, maybe it's OK.

So if the wires are swapped then your lambda ECU is not working. The ECU should get it's power from the same relay that powers the FV wire. You can try unplugging the connector on the lambda ECU and plug it in again in case there is a bad connection there.

[jawn101]

I just put the OEM lambda relay back in with the same result - clicks on when I jumper the RPM relay but no activity from the FV. I've plugged and unplugged the lambda computer several times but it doesn't seem to have helped. Crap. Any other tests to try before I just go drop a ton of cash?

[Bitsyncmaster]

I just put the OEM lambda relay back in with the same result - clicks on when I jumper the RPM relay but no activity from the FV. I've plugged and unplugged the lambda computer several times but it doesn't seem to have helped. Crap. Any other tests to try before I just go drop a ton of cash?

You can mesure the voltage at the lambda connector power pin but it sounds like the ECU may have gone bad. I think I have a spare ECU if you want to try it.

[jawn101]

You can mesure the voltage at the lambda connector power pin but it sounds like the ECU may have gone bad. I think I have a spare ECU if you want to try it.

PM sent...

[jawn101]

Side note, how do you get the lambda computer out? The studs seem too long to slide it out without removing the whole metal tray, which I'm not seeing how to do.

[DeMopar]

Thanks Rich. I'll go over a bunch of this stuff tomorrow. I just don't know what could have suddenly gone so wrong just sitting for a week. I don't have any way of checking fuel pressure but maybe I'll have to invest in a test kit.


It's a Delorean. It doesn't need a reason for something to go wrong with it.:approve:

[David T]

Before you go pulling the Lambda ECU I would check, at the plug for the ECU, for power and ground. It is rare that the ECU goes bad and it would be a waste of time waiting for another one only to find out it won't work either. Pull out your Workshop Manual and go to D:04:12. Check for power on pin 8 (green/yellow) and ground on pins 5 (Black) and 16 (Black). I have found bad connections at the bulkhead connectors all the way up behind the coil cover but inside the car behind the rear package shelf. Just because you hear a relay clicking does not mean it is good. The contacts could be dirty but the relay still activates. Make sure you have power coming out of the Lambda relay on terminals 87 (green/yellow) and 87b (red/purple). Better yet, for testing purposes, just jumper 30 (brown) to both 87 and 87b. I would first make sure you have power on that brown wire from fuse #7. Inspect the terminals in the fuseblock where the relay plugs in. One or more could have backed out and is not gripping the terminals on the relay, only touching and not making good, consistent contact.
David Teitelbaum

[jawn101]

Before you go pulling the Lambda ECU I would check, at the plug for the ECU, for power and ground. It is rare that the ECU goes bad and it would be a waste of time waiting for another one only to find out it won't work either. Pull out your Workshop Manual and go to D:04:12. Check for power on pin 8 (green/yellow) and ground on pins 5 (Black) and 16 (Black). I have found bad connections at the bulkhead connectors all the way up behind the coil cover but inside the car behind the rear package shelf. Just because you hear a relay clicking does not mean it is good. The contacts could be dirty but the relay still activates. Make sure you have power coming out of the Lambda relay on terminals 87 (green/yellow) and 87b (red/purple). Better yet, for testing purposes, just jumper 30 (brown) to both 87 and 87b. I would first make sure you have power on that brown wire from fuse #7. Inspect the terminals in the fuseblock where the relay plugs in. One or more could have backed out and is not gripping the terminals on the relay, only touching and not making good, consistent contact.
David Teitelbaum

David - thank you for pointing out that diagram in the manual. I must have passed it over when I was looking for exactly this info. The diagram I have of the Lambda circuit didn't have the pinout for the ECU connector in enough detail for me to test anything. I will give that a shot tonight as well. I wonder if that red-tagged ground cable could have come unhooked from the block, isn't that a dedicated ground for the ECU? Definitely need to go look at that.

[jawn101]

OK, worth a try but bad news. New lambda relay installed, RPM relay jumpered.

Pin 8 (GY from Lambda relay) to ground (touching the metal tray) - 12v.
Pin 8 (GY) to pin 5 (Black - ground) - 12v
Pin 8 (GY) to pin 16 (Black - ground) - 12v

Is there any value in jumpering pins 8 and 15 on the connector to see if the FV runs? Or is that not how the circuit works. I honestly don't know.

[Bitsyncmaster]

OK, worth a try but bad news. New lambda relay installed, RPM relay jumpered.

Pin 8 (GY from Lambda relay) to ground (touching the metal tray) - 12v.
Pin 8 (GY) to pin 5 (Black - ground) - 12v
Pin 8 (GY) to pin 16 (Black - ground) - 12v

Is there any value in jumpering pins 8 and 15 on the connector to see if the FV runs? Or is that not how the circuit works. I honestly don't know.

You have to get the metal try moving to pull the ECU out. But you can test another ECU first without pulling the old one out.

Not sure what you test results state. Looks like you have a broken ground wire?

[Bitsyncmaster]

Just to note:

If your car primes hitting the throttle many times, you probably don't have the capacitor on the idle speed micro switch. It only seems to cause problems sometimes with my dome light unit without that capacitor.

[David T]

Do not hook the FV directly up to a full 12 volts. It may burn it out. You can try removing and replacing the plug on the FV. Once in a while that is enough to get it going, the contacts get dirty. Also verify the plug to the FV, one wire is going to ground. Sometimes the connector gets knocked off or while working in that area you forget to put the wire back on the block.
David Teitelbaum

[jawn101]

Do not hook the FV directly up to a full 12 volts. It may burn it out. You can try removing and replacing the plug on the FV. Once in a while that is enough to get it going, the contacts get dirty. Also verify the plug to the FV, one wire is going to ground. Sometimes the connector gets knocked off or while working in that area you forget to put the wire back on the block.
David Teitelbaum

I've removed and reinstalled that plug 20 times during my troubleshooting. I've also cleaned both ends of the connector.

Roger on not powering the FV directly.

If my tests of the ECU connector showed voltage from pin 8 (hot from Lambda relay) to pins 5 and 16, doesn't that mean that the path to ground is good? I saw the same voltage when testing pin 8 straight to the metal mounting tray. To me that says at least those wires are OK.


Just to note:

If your car primes hitting the throttle many times, you probably don't have the capacitor on the idle speed micro switch. It only seems to cause problems sometimes with my dome light unit without that capacitor.

Dave - you're right, I don't believe I have the capacitor (should just be hanging off a short length of yellow wire, right?) on the idle speed switch. And I have had some odd problems with your dome timer, as I'm sure you remember :) My harness is the very early style one, is the capacitor something I should seek out and add?

[David T]

Put a dwell meter on the diag plug and see if you are getting any readings. At this point it may be time to suspect the ECU if the voltage readings you are getting are accurate.
David Teitelbaum

[jawn101]

Put a dwell meter on the diag plug and see if you are getting any readings. At this point it may be time to suspect the ECU if the voltage readings you are getting are accurate.
David Teitelbaum

I tried that as well, but didn't mention it - sorry. I don't use the diag plug because for some reason my meter works better if you directly backprobe the 2-pin bulkhead connector to the FV. With the RPM relay jumpered (but the motor not running) there was no duty cycle evident.

[Ron]

You might try checking those 12V readings with a load...using say, an icepick testor or similar...

[Bitsyncmaster]

Dave - you're right, I don't believe I have the capacitor (should just be hanging off a short length of yellow wire, right?) on the idle speed switch. And I have had some odd problems with your dome timer, as I'm sure you remember :) My harness is the very early style one, is the capacitor something I should seek out and add?

Mine never had that cap. It is installed on some cars in on the intake manifold but most cars don't have it. I just installed a 1 uf in the wires to the switch. I also added a diode to clamp reverse spikes but you probalby don't need that.

[jawn101]

You might try checking those 12V readings with a load...using say, an icepick testor or similar...

Anything special to do there or just slap the test light across the same points and see if it turns on?

[Ron]

No that's it.
Idea is that a meter will read the voltage but the circuit may only be able to handle the smallest of amperages due to a poor connection etc....

[Bitsyncmaster]

No that's it.
Idea is that a meter will read the voltage but the circuit may only be able to handle the smallest of amperages due to a poor connection etc....

Just put a 12 light bulb on your meter leads as your reading the voltage. I bet that would be a good thing to have....a banna plug adaptor that plugs into the meter plugs and the leads plug into that. I may make one up.

[jawn101]

Just put a 12 light bulb on your meter leads as your reading the voltage. I bet that would be a good thing to have....a banna plug adaptor that plugs into the meter plugs and the leads plug into that. I may make one up.

OK, will try to gin something up tonight.

[Ron]

Just put a 12 light bulb on your meter leads as your reading the voltage. I bet that would be a good thing to have....a banna plug adaptor that plugs into the meter plugs and the leads plug into that. I may make one up. Works great! ...I bought a set of adapters a long time ago off of a MAC truck that slip right over the probe needles: lamp, alligator clamp(s), sharp piercing tip, etc
:thumbup2:

[jawn101]

Alright, so I got an el-cheapo test light at HF on the way home. Wired it up to my DVM with some bullet connectors and repeated my measurements - light came on, DVM reading 12v (slightly lower, 11.9 something) across pins 8 and 5, pins 8 and 16, and 8 direct to ground. So I guess the wiring is good and the voltage is there. Perhaps I'm just one of those lucky few with a bad computer.

[vwdmc16]

While your trying to figure out this ECU issue, you should still be able to get the car derivable with original power. Warm it up and start tweaking the CO adjustment a little at a time and drive around the block. Our cars should be able to run fine without the Lamda system operating, many owners have and do run that way. We dont know of its lean or rich but if you cant get it running properly when warm after turning the CO screw up to one turn in either direction, then maybe you do have main fuel pressure issues too. Ill try to get over and help this Saturday.

[jawn101]

Yeah, I was trying to avoid screwing with the mixture too much since its so dead on right now, maybe we can swap computers and see what happens. I also plan to pull the fuel pump tomorrow when I know I have time and see if the pickup hose has finally failed or something.

[vwdmc16]

I can bring my spare, with a spring inside too

[David T]

You could have a problem with the pick-up hose but if your FV is not buzzing that has nothing to do with it.
David Teitelbaum

[jawn101]

OK, so thanks to Dave M I have a known good lambda computer in my car now. Problem is I am still seeing the same behavior. Jumping the RPM relay activates the lambda relay but the FV is still dormant.

Now I'm really at a loss. Is there any way of testing the electronic function of the frequency valve? It seems like it must be at fault, but it's so expensive and such a rare failure that I feel like I need to verify it somehow first.

[Bitsyncmaster]

OK, so thanks to Dave M I have a known good lambda computer in my car now. Problem is I am still seeing the same behavior. Jumping the RPM relay activates the lambda relay but the FV is still dormant.

Now I'm really at a loss. Is there any way of testing the electronic function of the frequency valve? It seems like it must be at fault, but it's so expensive and such a rare failure that I feel like I need to verify it somehow first.

If you have a meter that can read frequency and or dwell, you should put the meter leads on the two FV leads. I think the frequency is 70 Hz. Dwell would be 45 degs on a cold engine. If you get those reading and still no buzz then it must be the FV has gone bad. Is there another owner in your area that you could borrow his FV to test?

[jawn101]

If you have a meter that can read frequency and or dwell, you should put the meter leads on the two FV leads. I think the frequency is 70 Hz. Dwell would be 45 degs on a cold engine. If you get those reading and still no buzz then it must be the FV has gone bad. Is there another owner in your area that you could borrow his FV to test?

Reading 13 deg on the 8 cyl, 18 on the 6. So I guess that the dwell is 26 (doubling 8 cyl)

That seems far too low. This is with the engine off and the rpm relay jumpered.

[Bitsyncmaster]

Reading 13 deg on the 8 cyl, 18 on the 6. So I guess that the dwell is 26 (doubling 8 cyl)

That seems far too low. This is with the engine off and the rpm relay jumpered.

Measure the resistance of the FV.

[jawn101]

Measure the resistance of the FV.

On the 200 ohm scale the FV reads about 16.5 when disconnected.

Note that I took the dwell angle readings directly off the white FV plug so it was disconnected at the time.

I reconnected the FV and took new dwell readings. 18 on the 8 cyl and 24 on the 6. So now 36 degrees?

Also hitting the full throttle switch does not change the reading. Not sure if that's because the motor is off but it should be energized when the ECU is, right?

[Bitsyncmaster]

On the 200 ohm scale the FV reads about 16.5 when disconnected.

Note that I took the dwell angle readings directly off the white FV plug so it was disconnected at the time.

I reconnected the FV and took new dwell readings. 18 on the 8 cyl and 24 on the 6. So now 36 degrees?

Also hitting the full throttle switch does not change the reading. Not sure if that's because the motor is off but it should be energized when the ECU is, right?

That looks to high. Mine is 2.7 ohms. Make sure you read the resistance correctly. You need to press hard on the pins (I checked it on the unplugged bulkhead connector).

Also take a reading of the meter probes shorted togeather.

[jawn101]

That looks to high. Mine is 2.7 ohms. Make sure you read the resistance correctly. You need to press hard on the pins (I checked it on the unplugged bulkhead connector).

Also take a reading of the meter probes shorted togeather.

Right you are. My crap HF meter read 26 ohms shorted to itself. Went and got my fluke and it reads 2.7 ohms on the unplugged bulkhead connector.

[Bitsyncmaster]

Right you are. My crap HF meter read 26 ohms shorted to itself. Went and got my fluke and it reads 2.7 ohms on the unplugged bulkhead connector.

Well the coil is not open or shorted. I guess the inside could have got plugged but don't know if that is probable. Was your dwell reading that HF meter also?

[jawn101]

Well the coil is not open or shorted. I guess the inside could have got plugged but don't know if that is probable. Was your dwell reading that HF meter also?

No sir, for that I use the same Actron analogue one that most people on here seem to have. It's served me well for dwell readings. I had a very hard time picking up a signal from backprobing the bulkhead connector with the FV connected today so I have been using the orange/purple leads to the diag connector

[jawn101]

Ok so as I typed that I think I realized my mistake. I moved the ground off the purple wire and to the block, leaving + on the orange wire.

Dwell is now a steady 50 degrees on the 4 cyl scale. Pressing the full throttle switch makes no difference. Could it be that the full throttle switch is stuck closed? I will have to remove my mixture unit to access the plug for that as I rerouted my harness slightly for cosmetic reasons. But if it was forcing the computer into full enrichment that might answer a lot of questions....

Edit: switch would be closed not open

[jawn101]

Ok. I only had to pull the W pipe so that was lucky. Disconnecting the full throttle switch didn't change anything.

Edit: my dumb ass removed the jumper that's why the bulkhead was dead.

[DMC5180]

Pull the connector and make sure you don't any pins pushed back. That happened to me once with the WUR heater wire.

[jawn101]

Thanks Dennis - it doesn't *look* like that's a problem since it was my fault the bulkhead connector wasn't working.

So here's where I'm at. This picture gets more and more confusing to me all the time.

- FV is not buzzing when the car is running
- Removing the RPM relay and jumpering the power pins does actuate the fuel relay (which is of the correct type) but the FV does not start
- I have tested the power and ground pins to the ECU and they are good (12v and carrying current with a test light)
- I have swapped ECUs and it did not help
- I have swapped fuel relays and it did not help
- Reading the dwell across the two pins at the bulkhead or at the diagnostic plug shows very low numbers. I am not 100% certain if I was reading it right in an earlier post; should it be the orange pin at the diag connector and ground to the block, or do you take readings from the orange pin and the purple pin? If orange to block, the dwell was about 50 (and that was much higher than I was seeing across the two pins at the bulkhead). If orange to purple, the dwell was about 25ish, and the same at both test locations.
- Pressing the FTE microswitch does not change the dwell readings
- Disconnecting the FTE microswitch does not change the dwell readings

So now I am left wondering why the dwell is reading so low. I would guess the valve is not running because the duty cycle is messed up. But I don't know what would cause that at this point.

[David T]

Even if the FV was plugged up (inside for the fuel) it should still buzz. Go back to D:04:12. Measure for 12 volts on the red/purple wire at the connector to the FV when the Lambda relay is energized. Then check for continuity from pin 15 at the plug for the Lambda ECU to the plug at the FV that's the red/brown wire. As you can see in that diagram it is possible for the Lambda relay to power the ECU yet if one side of the relay is bad you might not get power to the FV. Or it could be a bad connection somewhere on the RP or RN wires feeding the Frequency Valve.
David Teitelbaum

[jawn101]

Even if the FV was plugged up (inside for the fuel) it should still buzz. Go back to D:04:12. Measure for 12 volts on the red/purple wire at the connector to the FV when the Lambda relay is energized. Then check for continuity from pin 15 at the plug for the Lambda ECU to the plug at the FV that's the red/brown wire. As you can see in that diagram it is possible for the Lambda relay to power the ECU yet if one side of the relay is bad you might not get power to the FV. Or it could be a bad connection somewhere on the RP or RN wires feeding the Frequency Valve.
David Teitelbaum

One of the pins to my FV does have 12v (11.8 ) on it. The other has only a few tenths of a volt.

[jawn101]

So if I'm reading the schematic correctly, the thermal switch in the Y-pipe could also be driving the computer to full enrichment... right? It's in series with the FTE switch. That's way in the valley though, is there any value in digging that deep to disconnect it and see what happens?

[Ron]

Thanks Dennis - it doesn't *look* like that's a problem since it was my fault the bulkhead connector wasn't working.

So here's where I'm at. This picture gets more and more confusing to me all the time.

- FV is not buzzing when the car is running
- Removing the RPM relay and jumpering the power pins does actuate the fuel relay (which is of the correct type) but the FV does not start
- I have tested the power and ground pins to the ECU and they are good (12v and carrying current with a test light)
- I have swapped ECUs and it did not help
- I have swapped fuel relays and it did not help
- Reading the dwell across the two pins at the bulkhead or at the diagnostic plug shows very low numbers. I am not 100% certain if I was reading it right in an earlier post; should it be the orange pin at the diag connector and ground to the block, or do you take readings from the orange pin and the purple pin? If orange to block, the dwell was about 50 (and that was much higher than I was seeing across the two pins at the bulkhead). If orange to purple, the dwell was about 25ish, and the same at both test locations.
- Pressing the FTE microswitch does not change the dwell readings
- Disconnecting the FTE microswitch does not change the dwell readings

So now I am left wondering why the dwell is reading so low. I would guess the valve is not running because the duty cycle is messed up. But I don't know what would cause that at this point.You measure from the orange pin to ground (the purple wire has 12v on it).
look here http://dmctalk.org/showthread.php?5760-Adjusting-CO-With-A-Dwell-Meter first pic in post #9 and you can tell that the orange wire at the pin and bulkhead connectors is the same wire.

NOTE:
O2 sensor disconnected can give 40° -50° steady
Full throttle switch (or shorted) gives 50° steady

[jawn101]

You measure from the orange pin to ground (the purple wire has 12v on it).
look here http://dmctalk.org/showthread.php?5760-Adjusting-CO-With-A-Dwell-Meter first pic in post #9 and you can tell that the orange wire at the pin and bulkhead connectors is the same wire.

NOTE:
O2 sensor disconnected can give 40° -50° steady
Full throttle switch (or shorted) gives 50° steady




Roger. That's the one (orange to ground) that gave me 50 steady.

So the full throttle switch or a disconnected O2 sensor could cause that? I've disconnected the full throttle switch and it didn't seem to help. I checked the O2 and it looks connected but its hard to tell since the tab is so deep. I'll check that again. Would the O2 sensor factor in to a cold engine (not even running) via resistance or something?

Any merit to my guess about the thermal switch in the Y pipe?

Thanks a lot Ron. :)

[Ron]

Would the O2 sensor factor in to a cold engine (not even running) via resistance or something?

Any merit to my guess about the thermal switch in the Y pipe?

I'd be guessing with the engine not running...

But Running-
Below 59F gives 50° to 60° steady too (actually what the manual gives for the WOT switch... see D:04:15 for all)
That is the normal reading for a cold engine!, ...you got it..., detected by the thermal switch....

[jawn101]

I'd be guessing with the engine not running...

But Running-
Below 59F gives 50° to 60° steady too (actually what the manual gives for the WOT switch... see D:04:15 for all)
That is the normal reading for a cold engine!, ...you got it..., detected by the thermal switch....

Hmm. Well that certainly aids the troubleshooting but I'm not loving what I hear... :)

It's definitely about that temp here right now. So 50 degrees is pretty much correct. But no buzz. So the wiring and computer is good but the valve is probably bad - is that a reasonable conclusion?

Anyone have a spare one...? :)

[Ron]

I'm multi tasking like a mofo right now...but w/o reading through again, I'm thinking if it is cold and reading 50 at idle, it's doing what it is supposed to...if it is running, which makes it hard to tell if it is buzzing...did you try something like using a long extension against the FV and you ear to listen to it rather than feel it?

sorry if you said earlier...(I was just filling in potiential holes I spotted as I skimmed through....)

[jawn101]

I'm multi tasking like a mofo right now...but w/o reading through again, I'm thinking if it is cold and reading 50 at idle, it's doing what it is supposed to...if it is running, which makes it hard to tell if it is buzzing...did you try something like using a long extension against the FV and you ear to listen to it rather than feel it?

sorry if you said earlier...(I was just filling in potiential holes I spotted as I skimmed through....)

Didn't try that. Tomorrow I'll seal up the W pipe again and hook everything up for some running tests. Will try the extension against the valve too and report back, that's a trick I always forget about.

[jawn101]

Out of curiosity... Is anyone near their car? Can you unhook your full throttle micro switch and read continuity across the green and black wires at the harness side? Mine is reading a clean path, which I do not think it should.

[Bitsyncmaster]

Out of curiosity... Is anyone near their car? Can you unhook your full throttle micro switch and read continuity across the green and black wires at the harness side? Mine is reading a clean path, which I do not think it should.

My switch is removed so can't test it but I think the Lambda ECU is a high impedance but you should see a Meg-ohm or less. I think the thermal switch that shares that circuit is a switch so it would be shorted below 59 degrees and open above that.

[jawn101]

My switch is removed so can't test it but I think the Lambda ECU is a high impedance but you should see a Meg-ohm or less. I think the thermal switch that shares that circuit is a switch so it would be shorted below 59 degrees and open above that.

I just tore the whole motor down to the valley to inspect the length of the engine main harness and verify that the thermal switch was still connected correctly. No issues found. Put the whole thing back together and while it's exactly as good as before, the issue is still present. Solid 50 degrees of dwell; both with the motor off and RPM relay jumped and with the RPM relay installed and the cold motor running. No FV action is evident. I tried using a screwdriver to listen to it but there's a lot of noise right there.

For grins I also tried connecting a new O2 sensor to the computer instead of the one installed in the exhaust. That didn't make any difference either.

OT: big thanks to Clint/#1768 for teaching me so well, I'm a total newb and this is the first car I've ever worked on. 2 years later and I did a complete valley teardown and rebuild with the whole thing perfect (well, exactly as good as when I started) on the first try in only 3 hours. Gave me a chance to clean out some of the gunk and coolant that accrued when my hot water valve blew a few months ago.

[Ron]

I tried using a screwdriver to listen to it but there's a lot of noise right there.
When I first got my D the FV was not strapped to the valve cover. It worked OK and it was very easy to tell if it was buzzing or not just holding it....

[jawn101]

When I first got my D the FV was not strapped to the valve cover. It worked OK and it was very easy to tell if it was buzzing or not just holding it....

Yes, mine too. That's why I know for sure that it's not going right now :) At least not at the normal cycle. It could be going at a much slower and thus quieter rate.

So I guess the question now is: could the strange dwell reading be a symptom of a bad valve, or is the valve likely OK and I should keep chasing other gremlins?

[jawn101]

At this point I'm thinking out loud here.

I found this thread that some of you same guys weighed in on in the past: http://www.dmchelp.com/showthread.php?2266-Frequency-Valve-has-no-dwell-signal&

I pulled out my relay strips and checked the voltage there from the underside with the lambda relay installed. The ground pin to the red/purple wire (frequency valve) got a solid 11.98v when I jumped the RPM relay. The ground pin to the the green/yellow wire showed the same thing. Both pins were dead without the jumper installed. So the wiring inside the car seems OK at this point. The relay is clearly working, the computer is receiving power - that was verified in an earlier post with a test light and DVM, plus there is a dwell signal at the diagnostic plug.

I guess at this point the most likely culprit is the valve itself then. I'll have to beg some local folks to see if they'll be so kind as to loan their valve for a test. I've been trying really hard not to go that route as I think it's a huge ask for someone to open a sealed fluid system for my benefit. If it turns out that it's just a bad valve, is there any way to resurrect them? I see that Hervey offers a "cleaning" type service for the CSV which is basically the same thing in a slightly different package; could it just be gummed up?

[vwdmc16]

Wow Jon, a solo valley tear down! im impressed and proud! Did you get the full throttle harness resistance readings? I can get that for you right now. I just put my throttle and W pipe back together and I cut off the auto kick down wiring and cleaned up the FTE wiring, I was always getting the two plugs mixed.

[jawn101]

Wow Jon, a solo valley tear down! im impressed and proud! Did you get the full throttle harness resistance readings? I can get that for you right now. I just put my throttle and W pipe back together and I cut off the auto kick down wiring and cleaned up the FTE wiring, I was always getting the two plugs mixed.

Hell yeah, it went way better than expected. I lost a socket extension inside the mixture unit but I figure it will just fall out eventually.

Just kidding, I got it out... :lol:

I didn't do a resistance reading on the harness, no. I'm starting to think that valve is just bad. A few months ago I tore apart my starter solenoid trying to find a faulty thermotime switch. I should have learned my lesson from that experience, that the simplest explanation usually ends up being the correct one, right? I'm just so used to hearing people say that those valves never fail.

I put a sharpie mark on my FTE plug so I don't mix it up with the kickdown plug. Seems silly that they used the exact same colors and everything on those.

[Ron]

I put a sharpie mark on my FTE plug so I don't mix it up with the kickdown plug. Seems silly that they used the exact same colors and everything on those.

The Thermal Throttle Enrichment Switch and Full Throttle Enrichment Switch wires have the same colors because they are the same exact wire (Light Green). [Either switch can tell the ECU to go to 50°-60° steady dwell by grounding pin 7 !]

The (Automatic) Kick Down Switch is Light Green with Green stripe. [GC downshift request]

[jawn101]

The Thermal Throttle Enrichment Switch and Full Throttle Enrichment Switch wires have the same colors because they are the same exact wire (Light Green). [Either switch can tell the ECU to go to 50°-60° steady dwell by grounding pin 7 !]

The (Automatic) Kick Down Switch is Light Green with Green stripe. [GC downshift request]

Ah, I guess I didn't look close enough :) Thanks Ron.

Going to try out a friend's frequency valve this weekend and hopefully that will lay this whole matter to rest. If not, stand by for more questions... ;)

[dmc3130]

Hey John,

I hope you get this all figured out soon. If there is anything I can do to help let me know!! :wrenchin:

[shadowfax101]

I have a spare FV that I know works if you need an extra for a while. Its in rough shape, but it does work.

[vwdmc16]

Im coming over with my known working car tomorrow morning, We will replace everything until we find the fault!

[jawn101]

Hey John,

I hope you get this all figured out soon. If there is anything I can do to help let me know!! :wrenchin:


I have a spare FV that I know works if you need an extra for a while. Its in rough shape, but it does work.


Im coming over with my known working car tomorrow morning, We will replace everything until we find the fault!

Thanks to everyone, this is why I love this forum :) Everyone is always so supportive and helpful and I've met some great people. Here's hoping we can make some progress with Clint's car - I have a feeling it will be a quick job of swapping the FV and testing both cars; I've already pretty much eliminated everything else at this point!

At least, I hope that's how it goes.... :)

[jawn101]

Good news! We fixed the issue.

After running a whole battery of tests on my car and then duplicating them on Clint's, we were completely baffled that everything was checking out perfectly. We even moved my valve to his car and it worked perfectly. Eventually we got around to checking the current flow (not just the voltage as I was doing) to the FV and discovered there was virtually none on my car.

So the issue turned out to be a bad connection on the R/B wire at the bulkhead connector. We removed the rear wall and pushed the connector through so we could solder the bullet connector to the wire for a better joint and voila! Everything back to normal. It was a pretty easy fix and free to boot. I will have to spend an afternoon putting the interior back together but that's a small price to pay.

Thanks to all for the help and generosity on this one.

[DeLorean03]

Well done, sir. You REALLY put your time in on this one. I highly respect everything you did to find that issue. Well done! Which bulkhead connector was it (color) ? I would love to know for future reference.

Also, was your problem like...you were driving down the road and then all of a sudden the car felt like it had no power for less than a second - almost like it was about to just die... and then everything was good and the car continued to drive like nothing had ever happened? I was just trying to understand what your symptoms were.

[vwdmc16]

This was a tricky one Jon, but it makes sense now, .20 Miliamps cantopen the FV, It needs like 1.6 Amp like my car has.


Now to find a good replacement connector set up to swap for those shitty stock connectors that have no weatherproofing.

[kings1527]

Good news! We fixed the issue.

After running a whole battery of tests on my car and then duplicating them on Clint's, we were completely baffled that everything was checking out perfectly. We even moved my valve to his car and it worked perfectly. Eventually we got around to checking the current flow (not just the voltage as I was doing) to the FV and discovered there was virtually none on my car.

So the issue turned out to be a bad connection on the R/B wire at the bulkhead connector. We removed the rear wall and pushed the connector through so we could solder the bullet connector to the wire for a better joint and voila! Everything back to normal. It was a pretty easy fix and free to boot. I will have to spend an afternoon putting the interior back together but that's a small price to pay.

Thanks to all for the help and generosity on this one.

Nicely done, Jon. I've been following this thread for future reference.

I looked at the bulkhead connector sheet I have and was wondering exactly which wire this one was. On the form, I show the white bulkhead connector number 53 and 54 both dealing with the frequency valve but those colors don't correlate to the one you mentioned. Was it one of those?

Alex
6575

15363

[jawn101]

Well done, sir. You REALLY put your time in on this one. I highly respect everything you did to find that issue. Well done! Which bulkhead connector was it (color) ? I would love to know for future reference.

Also, was your problem like...you were driving down the road and then all of a sudden the car felt like it had no power for less than a second - almost like it was about to just die... and then everything was good and the car continued to drive like nothing had ever happened? I was just trying to understand what your symptoms were.

Actually, it was more like an immediately obvious lack of power as soon as I pulled out of my garage one day. I barely made it a mile (limped along to try and feel out the problem) before it became clear I was going to have to coast home. Basically the mixture was so off that there was incomplete combustion - popping in the motor, lots of noise but absolutely no power. Stomping the pedal yielded next to no additional acceleration. It was near impossible to start from a stop without stalling out, the motor was struggling to idle, etc. Just goes to show how important the mixture is.


This was a tricky one Jon, but it makes sense now, .20 Miliamps cantopen the FV, It needs like 1.6 Amp like my car has.


Now to find a good replacement connector set up to swap for those shitty stock connectors that have no weatherproofing.

Yeah, those connectors are clearly inferior. But at least it didn't appear that water intrusion or corrosion was the problem here, right? Just a very bad connection on one of the pins.


Nicely done, Jon. I've been following this thread for future reference.

I looked at the bulkhead connector sheet I have and was wondering exactly which wire this one was. On the form, I show the white bulkhead connector number 53 and 54 both dealing with the frequency valve but those colors don't correlate to the one you mentioned. Was it one of those?

Alex
6575

15363

Credit where it's due. I did a lot of wrench turning but the guys here on the forum and Clint were really instrumental in figuring out this problem. It was very daunting because everything seemed to be completely perfect, until we finally ran the correct (and only) test that showed it wasn't.

The connector was the 2-pin white connector on the bulkhead, #s 53 and 54 on the PDF you linked. There are different versions of the engine harness and it appears the early one had different color wires than are listed there. Mine (and Clint's, both early cars) are Red/Brown on top (typo on my part in my last post) and Red/Purple on the bottom. The Red/Brown wire was the bad connection, which is a pulsed ground from the Lambda ECU. See attached photo.

Thanks again for the help everyone.

[Bitsyncmaster]

Good job. Those bulkhead connectors are a cause of many problems. I've found those round pins (sockets) just do not maintain pressure on the pin. Not sure why since a new socket pin crimped on seems to fix it. Maybe they got a bad lot of sockets when they made our cars.

Now I had one bad connection that was on the crimp side of the pin and not the mating of the pins themselves. This is probably what you found since you pulled and pushed that connector many times.

[Tillsy]

Ouch, yes I've caused intermittent problems with those same connectors at the rear, in one of my doors, and on front harness simply by disturbing something nearby. In each case I've had to bend each of the sockets in the connector(s) to make a better fit and my problems never returned!

My rear harness symptom was a stall any time there was the slightest bump - so after working back there a couple months back I reversed out my driveway and instantly stalled, then continued to do so each time there was a slight bump in the road until eventually she would not restart. Never worked out which of the many pins back there was the culprit but tightening the fit of all of them fixed it up.

After causing these issues in three different places I now make it a habit to clean and tighten any connector I see within visible range of where I'm working - after 30 years gotta expect things to get a bit pissed at seeing daylight I guess :)

[Ron]

Good job guys!

Hindsight now of course, but for future reference, you can check ground connections for handling a load the same as you did power sources by connecting one end (of ice-pick probe) to battery (+) and the other to what you want to test (the bigger the bulb the better).


:thumbup2: Clint !

[jawn101]

Good job. Those bulkhead connectors are a cause of many problems. I've found those round pins (sockets) just do not maintain pressure on the pin. Not sure why since a new socket pin crimped on seems to fix it. Maybe they got a bad lot of sockets when they made our cars.

Now I had one bad connection that was on the crimp side of the pin and not the mating of the pins themselves. This is probably what you found since you pulled and pushed that connector many times.

Yes, exactly - it was the wire to pin connection that was bad, not the pin to socket. Much harder to fix of course but now that joint is the strongest one rather than the weakest. One of these days I should pull all those connectors and solder them all. Ah well.

[Bitsyncmaster]

Yes, exactly - it was the wire to pin connection that was bad, not the pin to socket. Much harder to fix of course but now that joint is the strongest one rather than the weakest. One of these days I should pull all those connectors and solder them all. Ah well.

Mine was in the CSV circuit and mesured about 40 ohms. Finding that problem probably took as long as it took you to find yours.

[dmc3130]

Yes, exactly - it was the wire to pin connection that was bad, not the pin to socket. Much harder to fix of course but now that joint is the strongest one rather than the weakest. One of these days I should pull all those connectors and solder them all. Ah well.




Nice job John! That was great that Clint could come and help you out on this....So we are good for the parade! :clown:

[DavidProehl]

Glad to hear you got this figured out! What a pain to troubleshoot.

[jawn101]

Nice job John! That was great that Clint could come and help you out on this....So we are good for the parade! :clown:


Glad to hear you got this figured out! What a pain to troubleshoot.

Yep! I'm really glad too. Drove her to work today and it was a flawless experience :) Clint's the man for sure.