Lambda problem?

[delorean82]

Hello, hoping someone can help.

I did a complete tune up on my car and found it running rough and I got a glowing cat. So I was using an article in delorean world to check the co to see if I was running rich. Hooked up the dwell meter to the frequency valve correctly and bypassed so it runs constantly. My reading should be 45 if all is working correctly but I get like 88-90. The article says if you get that high of a reading the system isn't working properly. Any ideas as to where to start looking to fix the system? O2 sensor?

[DMCMW Dave]

Hello, hoping someone can help.

I did a complete tune up on my car and found it running rough and I got a glowing cat. So I was using an article in delorean world to check the co to see if I was running rich. Hooked up the dwell meter to the frequency valve correctly and bypassed so it runs constantly. My reading should be 45 if all is working correctly but I get like 88-90. The article says if you get that high of a reading the system isn't working properly. Any ideas as to where to start looking to fix the system? O2 sensor?

Yes, it should read 45 if you have jumped the RPM relay to turn on the lambda ECU.

88-90 is the same reading you get if the dwell meter isn't reading anything. Does the FV buzz when you test it like this? What dwell meter are you using? Some don't read the signal very well I've discovered. Try connecting the dwell meter backwards and see what you get.

Just a hunch here - make sure you didn't knock off the ground wire that comes off the back of the passenger intake runner, and goes about two inches to an inline connector (what were they thinking?). That's the ground reference for the ECU/O2 sensor and if disconnected it acts really strange. . .

[delorean82]

Thank you for the reply.

The FV is buzzing when I jumped it. I'm using a actron auto trouble shooter cp7677.
When I reversed the probes I got 73.2.

The ground on the intake is tight.
My current problems are that the engine runs rough and idles at 775, and I get a glowing cat. I do get occasional backfire at the plate under the aircleaner. What meter do you recommend or is the another way to hook this up?

Also before the work I did, my car used to hunt at start up. Now it doesen't hunt anymore. Maybe bad vacuum leak before?

[delorean82]

Is that ground the one with the red shrink tubing with a number on it?

[82DMC12]

Thank you for the reply.

The FV is buzzing when I jumped it. I'm using a actron auto trouble shooter cp7677.
When I reversed the probes I got 73.2.

The ground on the intake is tight.
My current problems are that the engine runs rough and idles at 775, and I get a glowing cat. I do get occasional backfire at the plate under the aircleaner. What meter do you recommend or is the another way to hook this up?

Also before the work I did, my car used to hunt at start up. Now it doesen't hunt anymore. Maybe bad vacuum leak before?

Try using an analog dwell meter with a needle. The digital circuitry might not like the swinging signal the lambda ecu is feeding it. I bought a cheap one at autozone a few years back.

Sent from my DROID BIONIC using Tapatalk

[David T]

Another thing I have noticed is that you do not always get a good ground connection at the diagnostic plug. Connect the ground lead off the dwell meter directly to the motor. If you are running way too rich you will not be hunting and the Lambda will not fluctuate. Start leaning the mixture out and get the cat to stop glowing. If you ran too rich for too long the O2 sensor may be overloaded and contaminated. It may have to be replaced.
David Teitelbaum

[DMCMW Dave]

Is that ground the one with the red shrink tubing with a number on it?

Yes, that's it.

[delorean82]

Thank you for all the help guys.
I'll try these suggestions tonight and post my findings. On the analog scale when you use the 8 cylinder section, do you just cut the value in half for 4 cylinder?

Noticed my injectors move left to right fairly easy, seals bad?

[lorentbj]

I do not know about Deloreans but it is common for injectors to easily rotate on other vehs.This does not make your seals bad. bob

[delorean82]

Ok here's what I got so far,

Went back to the digital meter after finding that it responded when grounding it at the block. Meter started 88 and moved down to 2.0. Then I tried this with the engine running and got the same. I did adjust the fuel mixture while the car was running to ward off a glowing cat but ended up getting it anyway. The car does backfire at the fuel mixture valve when I rev the engine. Still smells rich and runs rough but the idle sits at 775. The engine just shakes.

Any ideas?

[DMCMW Dave]

A glowing cat is much more serious than something being slightly out of adjustment.

Backfiring it usually a sign of a lean misfire, but a glowing cat at idle is usually something way too rich. Are you sure the fuel distributor isn't stuck? How long has the car sat before you starting tuning it up? Do you get the normal resistance to a finger push on the throttle plate just after turning it off?

[delorean82]

I do have normal resistance at the throttle plate, it doesn't seem to be loose.
The car sat for about 6 months while I did repairs to the brakes and body.
The cat doesn't glow right away the car warms up first and then it starts to get red hot.

Before I did the tune up, it ran well and smooth, and hunted on start up. Now it runs rough and no hunting. I never touched the timing, just replaced parts, and tried to adjust the co as per the article I was using. Still don't know why I cant get the dwell to show up.

[Bitsyncmaster]

If your way off on the mixture, the dwell will read about 10 or 80 degrees after it warms up. But when you first start it (or press the WOT), you should read about 45 degrees. That would show your dwell meter is working.

[delorean82]

Not getting 45 at start up or by pushing WOT.

Bad o2 sensor?

[Bitsyncmaster]

Not getting 45 at start up or by pushing WOT.

Bad o2 sensor?

No. My guess is your meter is not working since your getting a buzzing FV.

[DMCMW Dave]

Agree. Here's an easy test. Yank the RPM relay and jumper the brown wire to the yellow/red wire. Key does not need to be on. The RPM relay will start buzzing at 50% (45 deg). You can now test your circuit and meter to your hearts content without running the engine and melting things. When you have the meter working and reading 45 (55 if/when you hit the full throttle microswitch) then you can go back to troubleshooting the engine.

FYI - there is a series of simple tests given in the manual that are really handy to verify the electronics. (page D:04:05, paragraph 5). This seems mysterious to most but is works well.

If you disconnect the O2 sensor and GROUND the connector on the car (not the sensor) the dwell meter should read 87 degrees. You will hear the FV change pitch as it moves. If you put a 1.5V flashlight battery + on the car connection and ground the neg of the battery to the frame, you'll see the dwell swing to 20 deg. With the O2 sensor disconnected (or connected with the engine off) it should read 45 all the time.

[mluder]

I had a strong fuel smell and rough running engine. I tried adjusting the mixture with a duty cycle meter but could never get it dialed in just right so I bought a cheapy muilti meter with dwell from Harbor Freight.

Once I hooked it up after letting the engine warm up I discovered that what I thought was a rich mixture (fuel smell inthe exhaust) was actually a lean mixture. I richened it up and now it's running smoother and the gas smell seems to be gone. I think I might dare taking it through the DEQ and see if it'll pass emmisions.

I'm curious though... I have been using injector cleaner in the tank pretty regularly - my car had sat for 10 years before the previous owner got it running to sell. He re-did most of the fuel system but stopped short of replacing the injectors. DMCNW, who did the work) said to run injector cleaner through a few tanks. Can the injector cleaner in the fuel affect emmisions testing and cause it to read too many hydrocarbs? It would seem that injector cleaner should burn more efficiently. Any thoughts?

[delorean82]

Ok
I have two digital meters and one analog meter. Not getting any results from them.
Is it possible I'm connecting to the wrong connector? I'm using the white connector at the bulkhead with two wires coming from it with my multimeter. This the rear most plug with the group of other plugs.
Today I richend the mixture and the car seemed to smooth out a little, still get the glowing cat and rough idle. All plugs are firing and the timing is approx 12 degrees, allthough I made a rookie mistake and forgot to plug the vacuum advance.

Thoughts?

I really want my car to run normally but more importantly I just want to know what the he'll is going on?

[David T]

Another quick thought. Make sure the cold start valve is NOT squirting. It could be stuck, defective (rare) Wiring or switch problem, or you did the plug swap and it is running full open. Pull the plug off of it.
David Teitelbaum

[Bitsyncmaster]

Look at the second photo in post #9 of this thread.

http://dmctalk.org/showthread.php?1772-Dwell-Meter-how-do-you-hook-it-up

That orange wire is probably a better dwell signal than looking at the FV signals for some meters. That is where I always check the dwell. That connector is on the back firewall harness in the engine bay.

[delorean82]

Thank you for the tip on using the diagnostic plug to get a reading from. That worked great. FV tested out at 44.3. Replaced the o2 sensor and started the car, reading was 44.2 until it warmed up and then it went to 10. Seemed to run really smooth at 10, when I could hear the FV kick in the meter went 44 and ran rough. Then back to 10 after FV kicked off. Seems to me the car is running rich and needs to be adjusted up to get a consistent 44 or so before the FV kicks in. I'm I in understanding the correctly? It gets kinda to wrap your head around sometimes.

[Bitsyncmaster]

Thank you for the tip on using the diagnostic plug to get a reading from. That worked great. FV tested out at 44.3. Replaced the o2 sensor and started the car, reading was 44.2 until it warmed up and then it went to 10. Seemed to run really smooth at 10, when I could hear the FV kick in the meter went 44 and ran rough. Then back to 10 after FV kicked off. Seems to me the car is running rich and needs to be adjusted up to get a consistent 44 or so before the FV kicks in. I'm I in understanding the correctly? It gets kinda to wrap your head around sometimes.

You looking to adjust it to read about 30 to 35 degrees (average) after it is warmed up.

[delorean82]

Ok so I was able to get the car dialed in to 44 - 32.
But still getting the hot cat only near the muffler end of it, then the car just died. Wouldn't restart.

Does this sound like when I finally get it dialed in the cat was on it's way out and fianally went plugging the exhaust and casting the car to run poorly?

[Bitsyncmaster]

Ok so I was able to get the car dialed in to 44 - 32.
But still getting the hot cat only near the muffler end of it, then the car just died. Wouldn't restart.

Does this sound like when I finally get it dialed in the cat was on it's way out and fianally went plugging the exhaust and casting the car to run poorly?

My guess would be yes, your cat is plugged. You really need to pull it and look inside to know for sure. The honeycomb will melt when it gets that hot.

It's also very hard to set the mixture with a plugged cat. It will be changing every few minutes.

[delorean82]

That's what I thought, thanks for all the help. The car was Also sputtering like it was backfiring but wasn't . Tells me that it was just backed up with back pressure

[delorean82]

Ok so I took a break from this problem to read the book closely and found that I had actually mixed up number 3 with number 1 plug wires.

So car runs better, no hot cat. But now I have a new problem I still can't dial the fuel in with the dwell meter and I have a high idell. Rpm is about 900 to 950 when it used to be 750 consistently. I checked for vacuum leaks and only find a slight one at the w pipe where the o rings are but I replaced those.

As for the fuel I closed the mixture screw all the way, full lean, then opened it up until I got a decent fuel injector spray. Still cannot get the dwell meter to get off 84. It fluctuates between 84.3 and 84.7. When I push the WOT switch it goes down to 53.4.

Any ideas?

[DMCMW Dave]

Ok so I took a break from this problem to read the book closely and found that I had actually mixed up number 3 with number 1 plug wires.

So car runs better, no hot cat. But now I have a new problem I still can't dial the fuel in with the dwell meter and I have a high idell. Rpm is about 900 to 950 when it used to be 750 consistently. I checked for vacuum leaks and only find a slight one at the w pipe where the o rings are but I replaced those.

As for the fuel I closed the mixture screw all the way, full lean, then opened it up until I got a decent fuel injector spray. Still cannot get the dwell meter to get off 84. It fluctuates between 84.3 and 84.7. When I push the WOT switch it goes down to 53.4.

Any ideas?

You're still apparently running way too lean. What happens if you keep going richer? Does the idle speed up more or does the car sputter and slow down?

If you richen and now the idle is way too high, but it otherwise seems to run OK, you are compensating a vacuum leak. If you try and accerate but the car backfires or lacks power, you are more likely dealing with unmetered air leaks.

Your WOT switch test proves the ECU is working. You could do the service manual battery/ground O2 sensor test to verify that the ECU is working completely. Disconnecting the O2 sensor should get you to 45 degrees all the time, if that's not the case you are chasing other issues.

Common issues:
Unmetered Air Leaks (usually can be adjusted to idle OK but will lean misfire on acceleration and CO setting will seem erratic/lazy):
Idle Air pipe aka "the pipe of agony" not inserted all the way in;
Torn rubber gasket between the air metering assembly and the throttle;
Missing o-ring under the fuel distributor

Vacuum Leaks:
Disconnected brake booster or auto trans modulator hose;
Missing intake O-rings.

Sneak Air Path (internal air leak):
Stuck idle motor or disconnected idle thermistor (usually more like 2000 RPM idle)
Stuck/bad decel valve springs
Idle stop screws too far in
Brass idle screws open

[Bitsyncmaster]

I agree with Dave S. Your way to lean because the lambda is trying to make the mixture richer.

You idle speed just may be your curb idle is set to high. When the plugs were wrong it kept the idle speed down into the idle ECU control range. Make sure your three bypass screws are fully seated and then back out the lower screw on the idle arm.

[bluscreen]

Agree. Here's an easy test. Yank the RPM relay and jumper the brown wire to the yellow/red wire. Key does not need to be on. The RPM relay will start buzzing at 50% (45 deg). You can now test your circuit and meter to your hearts content without running the engine and melting things. When you have the meter working and reading 45 (55 if/when you hit the full throttle microswitch) then you can go back to troubleshooting the engine.

FYI - there is a series of simple tests given in the manual that are really handy to verify the electronics. (page D:04:05, paragraph 5). This seems mysterious to most but is works well.

If you disconnect the O2 sensor and GROUND the connector on the car (not the sensor) the dwell meter should read 87 degrees. You will hear the FV change pitch as it moves. If you put a 1.5V flashlight battery + on the car connection and ground the neg of the battery to the frame, you'll see the dwell swing to 20 deg. With the O2 sensor disconnected (or connected with the engine off) it should read 45 all the time.


I'm thinking my Actron meter may be dead. I'm troubleshooting an open loop issue and when I try the above test (car off, RPM relay wires jumpered) I hear the FV buzzing, but connecting the meter to an engine ground (or any ground) and onto the bottom-right diagnostic pin (or disconnecting that and using the orange wire directly) yields no output when the meter is set for Dwell. When set for RPM it shows 2-ish on the bottom 8-cyl scale, and when setting to volts it shows 5-ish. In fact, with the car running (and warmed up but still clearly in an open loop) the dwell setting still shows nothing. When running the RPM setting I think moves the needle over to a steady 10 if I recall correctly. Any wisdom for this? Is a new meter in my future?

(Brand new Bosch O2 sensor and confirmed continuity for it to the lambda ECU and also that it is grounding)

[Bitsyncmaster]

I'm thinking my Actron meter may be dead. I'm troubleshooting an open loop issue and when I try the above test (car off, RPM relay wires jumpered) I hear the FV buzzing, but connecting the meter to an engine ground (or any ground) and onto the bottom-right diagnostic pin (or disconnecting that and using the orange wire directly) yields no output when the meter is set for Dwell. When set for RPM it shows 2-ish on the bottom 8-cyl scale, and when setting to volts it shows 5-ish. In fact, with the car running (and warmed up but still clearly in an open loop) the dwell setting still shows nothing. When running the RPM setting I think moves the needle over to a steady 10 if I recall correctly. Any wisdom for this? Is a new meter in my future?

(Brand new Bosch O2 sensor and confirmed continuity for it to the lambda ECU and also that it is grounding)

The orange wire is the FV signal through a 1 kohm resistor. Try your meter on the three pin bulkhead connector red/ brown wire but my bet is your meter is NG.

[David T]

The orange wire is the FV signal through a 1 kohm resistor. Try your meter on the three pin bulkhead connector red/ brown wire but my bet is your meter is NG.

I have also seen problems with the connections in that large plug that goes into the Lambda control module. Make sure you have continuity from that plug all the way to the diagnostic plug. There can also be troubles in the bulkhead connectors where the ignition coil lives. Check the ground connections too.

[bluscreen]

Thank you both very much, I will try these suggestions asap. -Something- is coming through, as the needle moves a bit on the RPM and Volts settings as a mentioned.

[bluscreen]

The orange wire is the FV signal through a 1 kohm resistor. Try your meter on the three pin bulkhead connector red/ brown wire but my bet is your meter is NG.

Jumped the RPM wires and tried the meter (FV was buzzing loudly before I d/c the bulkhead connection) - 0 on dwell, 0 on RPM, but a decent reading on voltage - nearly half of the needle movement. Bad meter for sure?

David, thanks for this. I was able to get continuity from the diagnostic port to the lambda connector, about 10 ohms though. Bulkhead connector looks good and I'm not finding any bad grounds - really did a good once-over on them a few year ago (doesn't mean I haven't missed any - I saw a great thread will ground locations and will check each).

[Bitsyncmaster]

Jumped the RPM wires and tried the meter (FV was buzzing loudly before I d/c the bulkhead connection) - 0 on dwell, 0 on RPM, but a decent reading on voltage - nearly half of the needle movement. Bad meter for sure?

David, thanks for this. I was able to get continuity from the diagnostic port to the lambda connector, about 10 ohms though. Bulkhead connector looks good and I'm not finding any bad grounds - really did a good once-over on them a few year ago (doesn't mean I haven't missed any - I saw a great thread will ground locations and will check each).

The signal is a 50% square wave. That is why you read about 6 volts DC. It would also read AC voltage if you have another meter that reads that.

[bluscreen]

The signal is a 50% square wave. That is why you read about 6 volts DC. It would also read AC voltage if you have another meter that reads that.

That makes perfect sense, thank you. Should dwell have read anything? I should have a new meter tomorrow to compare against.

[Bitsyncmaster]

That makes perfect sense, thank you. Should dwell have read anything? I should have a new meter tomorrow to compare against.

Dwell compares the on and off time to give you a ratio number. So your meter should adjust the threshold mid way (about 6 volts) and do the compare there.

[bluscreen]

Dwell compares the on and off time to give you a ratio number. So your meter should adjust the threshold mid way (about 6 volts) and do the compare there.

I've always wondered - thank you for this!

Picked up the new meter last week... dwell setting now reads a value. Nice! Thank you both so much for responding here.