Adjusting dwell

[Kenthegreat]

My Delorean is running rich and I want to check the dwell, I borrowed a dwell meter and just wondering where is the best location to hook it up to? The meter has a red, black and an induction pickup. It's a Equus 3032. Any help will greatly appreciated.

[Jonathan]

I saw this while looking not long ago:


https://www.youtube.com/watch?v=cpNB1eRktzM

Not something I have any experience with, but the video makes it look simple.

Hope all is well out West, Ken. Say hello to the gang out there for me.

[Kenthegreat]

I don't have the diagnostic plug on my car! Still the video is great

QUOTE=Jonathan;174791]I saw this while looking not long ago:


https://www.youtube.com/watch?v=cpNB1eRktzM

Not something I have any experience with, but the video makes it look simple.

Hope all is well out West, Ken. Say hello to the gang out there for me.[/QUOTE]

[jmettee]

My Delorean is running rich and I want to check the dwell, I borrowed a dwell meter and just wondering where is the best location to hook it up to? The meter has a red, black and an induction pickup. It's a Equus 3032. Any help will greatly appreciated.

I didn't watch the video above, so not sure what it shows. Basically, red & black can be hooked to the battery positive stud on the passenger engine compartment wall & a metal part of the engine (I like the lift ring). There is also a positive (purple) & ground (black) in the diagnostic plug if you want to use them. The signal wire would attached to the pin in the diagnostic connector attached to the driver's side of the car, just under the resistors. It's a square connector with 9 pins in it. There is 1 pin you connect to for the dwell, but I forget which one. If your connector is missing, the orange wire should still exist in that area.

If you're out of range, or have a bad O2 sensor, your gauge will read steady around 10º or 90º. If all is working & you are in (or close to range), the needle should swing back & forth in about a +/-5º range. Ideal center of swing is either 40 or 45 (I forget which is stated in the manual).

[Jonathan]

I don't have the diagnostic plug on my car!

Naturally!!

If I'm not mistaken, you can pick-up the tach signal/RPM from one of the wires right at the coil. I'm not 100% certain which one though, so hopefully someone else will chime in. I remember asking about it one day as one of my wires in that area had a small bit of the insulation trimmed off and this is likely what a PO had gotten in there to do.

Or like Justin mentioned, if you don't have the diagnostic plug but can still find the right wire over there, that'll work.

[DMCMW Dave]

Naturally!!

If I'm not mistaken, you can pick-up the tach signal/RPM from one of the wires right at the coil. I'm not 100% certain which one though, so hopefully someone else will chime in. I remember asking about it one day as one of my wires in that area had a small bit of the insulation trimmed off and this is likely what a PO had gotten in there to do.

Or like Justin mentioned, if you don't have the diagnostic plug but can still find the right wire over there, that'll work.

Top left corner of the blue bulkhead connector. Orange wire.

[David T]

Naturally!!

If I'm not mistaken, you can pick-up the tach signal/RPM from one of the wires right at the coil. I'm not 100% certain which one though, so hopefully someone else will chime in. I remember asking about it one day as one of my wires in that area had a small bit of the insulation trimmed off and this is likely what a PO had gotten in there to do.

Or like Justin mentioned, if you don't have the diagnostic plug but can still find the right wire over there, that'll work.

You confused the ignition dwell with the duty cycle on the frequency valve. The dwell for the ignition system is not changeable.

[Kenthegreat]

I don't have a diagnostic plug, I have a connector that has the orange wire. So I tried using the meter that I borrowed and I could get any reading? Not sure if it works. So I used a multimeter to get a reading and I wasn't able to get it below 55 before it would stall? Engine is warmed up, it has new spark plugs, cap, rotor, oxygen sensor. I checked it over and all vacuum lines are good.

It's hard to tell but the frequency valve doesn't seam to be buzzing now, it was before. Should the frequency valve always be buzzing?

[Horsebox]

What are you trying to measure? Sounds like you want to know what your frequency valve is doing so you can see if it's doing anything about your mixture. It should always buzz. That video is good as you can hear the FV buzz, so you know what you're listening for. My take on the FV is that its job is to trim, or fine tune the mixture. Does this by sending more or less fuel back to the tank. If it's not working then you're going to be rich.

Assuming you want to know about your FV, follow post # 6 above, don't worry about not having a diagnostic connector. Just ground the negative lead to the engine and back feed the positive of the meter to the orange wire as per post 6.

A simple voltmeter won't tell you anything. You need one that can measure duty cycle, so it will tell you what percentage the FV is on.

Have fun!

[Bitsyncmaster]

Last week I tried my multimeter set to duty to read the duty cycle on the lambda. It read backwards. I flipped the leads and and it read nothing. I should have tried tying the black lead to +12 volts but did not think of it at the time. You can also read the duty directly off one of the FV wires which may have worked with that backwards reading meter.

So before you adjust the mixture, check your meter reading by pushing the wide open throttle switch. If you don't read 60% (or 54 degrees) then something is wrong with your meter reading.

[Kenthegreat]

My multi meter has a duty cycle setting and that's what I used, what would cause the frequency valve to stop working other than a failed frequency valve?



What are you trying to measure? Sounds like you want to know what your frequency valve is doing so you can see if it's doing anything about your mixture. It should always buzz. That video is good as you can hear the FV buzz, so you know what you're listening for. My take on the FV is that its job is to trim, or fine tune the mixture. Does this by sending more or less fuel back to the tank. If it's not working then you're going to be rich.

Assuming you want to know about your FV, follow post # 6 above, don't worry about not having a diagnostic connector. Just ground the negative lead to the engine and back feed the positive of the meter to the orange wire as per post 6.

A simple voltmeter won't tell you anything. You need one that can measure duty cycle, so it will tell you what percentage the FV is on.

Have fun!

[Bitsyncmaster]

My multi meter has a duty cycle setting and that's what I used, what would cause the frequency valve to stop working other than a failed frequency valve?

If you adjusted the mixture to far then you won't hear the FV buzzing. The FV is always running but at the extreamss 10% or 90% there is very little buzz you will hear. It's the loudest at 50%.

That is why I suggested testing your meter reading pressing the WOT switch. Reading the 60% doing that would verify your meter is reading correctly.

[DMCMW Dave]

My multi meter has a duty cycle setting and that's what I used, what would cause the frequency valve to stop working other than a failed frequency valve?

If the computer has driven the FV to fully open or close it will not buzz.

If you want to mess with this without running the engine, simply jump the brown and yellow wires together on the RPM relay. Ignition does not need to be on. This powers up the Lambda relay and ECU.

The frequency valve will buzz and the lambda will read 45 degrees (50%) all the time, and pressing the full throttle microswitch will take it to 55 (65%). If this does not work, fix the system before you start throwing parts at it.

What's the history on the car? If the frequency valve is stuck from sitting/bad gas, about 50% of the time (or more) a sharp smack with a small hammer to the side of the valve (on the metal!) will free it up.

[Kenthegreat]

After going thru everything I finally found it, one wire for the frequency valve was getting pressed back into the connector, so I got it set to 45, and yes when I hit the WOT switch it goes to 55-58 but now the engine just keeps reving at 2500 rpm, the car drives great it just the high idle, there's no intake leaks ( I checked with propane) the throttle is against the stop, throttle valve is moving freely. I took it off and cleaned the throttle valve and the butter fly valves move freely. it seams I have another issue to take of. What would cause the idle motor to stay open.

Thanks for everyone's help.

[Bitsyncmaster]

If the idle speed regulator circuit is broken, it will idle at 2500 RPM. By any chance did you pull on the harness to much at the back of the engine. The wires that may have come off goes into the VOD.

You can test if the circuit is open with an ohmmeter on two pins of the idle ECU connector. The black/yellow and black/slate will read about 50 K ohms cold and 1 K ohm hot.

[Kenthegreat]

The three wires that I have are black with green, black with pink (ish) and black with red. I replaced the wiring harness about a year ago, it was in very poor condition

[Bitsyncmaster]

Idle ECU is behind the drivers seat. ECU is a black box on top with two connectors. Pull the connector with 4 pins (4 wires). The black/yellow and black/slate wires (pins) is where you want to measure the resistance. Just touch your meter probes onto those pins (leave the connector unplugged during that test).

If your wire colors are different, post a photo.

[David T]

Idle ECU is behind the drivers seat. ECU is a black box on top with two connectors. Pull the connector with 4 pins (4 wires). The black/yellow and black/slate wires (pins) is where you want to measure the resistance. Just touch your meter probes onto those pins (leave the connector unplugged during that test).

If your wire colors are different, post a photo.

Make sure the throttle arm is hitting the idle micro. Check the decel valves in the throttle plates, sometimes the springs get weak and allow the valves to leak.

[Kenthegreat]

So I'm getting a 3.5 k ohm at the idle ecu, and the the screw is depressing the micro switch.

I took the car for a long drive today, it started to run really bad, stalled a few times. I had my meter with me and when I checked the duty cycle It was at 12? , didn't mater what I did it just kept reading 12. The frequency valve is working. The engine was running really. If you floored it while driving( hit the wot switch) it just stalled while driving, I pulled a spark plug wire and found the spark looked weak, I might have a bad ignition coil.

[Kenthegreat]

So I got 0.5 k ohms on the secondary coil and 9.04k ohms on the primary. According to a few web sites I got a weak coil.

[Bitsyncmaster]

So I got 0.5 k ohms on the secondary coil and 9.04k ohms on the primary. According to a few web sites I got a weak coil.

All good ignition coils have a very low resistance on the primary of a few ohms or less. Primary is read over two screw terminals (not to the case).

[Trstno1]

Can someone please post a good tutorial video on how to test the dwell with an Actron meter? Where to hook up the leads, what line on the meter you are supposed to read, what your readings actually mean, what they should be, etc etc, and how to troubleshoot high CO and rich running?

Sorry guys but I'm more confused ever after reading all the posts. I think I need to see it done in order to fully understand the procedure.

[Horsebox]

I tried to fix my mixture problem by going at the lambda system first. Don't bother, it's a red herring. Lambda just fine tunes the mixture for emissions reasons, nothing more.

If I were you I'd unplug the 02 sensor, make sure the frequency valve is operating at default 50%, then troubleshoot the fuelling with a pressure gauge.

[Jonathan]

How does my dwell reading look?


https://www.youtube.com/watch?v=y8tGu0b9_xA

I had a thread where I asked some question that led to Ron and others asking me "have you checked your dwell?" and now I can't find it. So I posted it here hoping for an opinion or two.

Just wondering if this is okay or not or what I should be seeing if this isn't it. I've had mixed messages on whether you should see the needle swing from one point and back again repeatedly or whether it staying in basically one place like mine does is the target.

[Chris 16409]

I use the same dwell meter that you are using. From what I understand, the needle should be swinging once the emissions system has entered "closed loop" operation. At this point the frequency valve is helping to meter fuel. On this meter you are supposed to read the upper scale of the dwell reading. The needle should be swinging between the 15 and 20 positions. For our purpose these numbers are doubled to 30 and 40 respectively. If you hold down the full throttle micro-switch, the needle should hold at the 25 position (or 50 in actuality). If you're needle isn't swinging, you might not be waiting long enough for the car to enter closed loop.

[Bitsyncmaster]

Your not going closed loop. As suggested, the engine has to be warmed up. Or your O2 sensor may be disconnected or faulty.

[Jonathan]

Is there a way to test if the O2 sensor is faulty or not? Mine was replaced about five years ago I would guess.

I can access the connector on the end of the sensor wire itself or I can access where those wires come in to meet the ECU connector behind the driver's seat.

I have a jumper in the back of my ECU right now and I wonder if it has affected this? It went in originally because my idle got stuck high, like 1,500 or 2,000 RPM high. The conclusion at the time was that the thermistor electrical connection had come undone. This is within the valley of the engine and a PITA to get at to reconnect. I put a jumper in on the back of the left side ECU connector such that the two wires that would go to the thermistor and back were jumpered directly to each other and then for those other two wires (that connector has four wires total) I made short jumpers just to sort of reconnect the connector and leave those unaffected. I can post a picture of what I mean if it isn't clear. The thought was that the thermistor was only needed during cold temperatures and wouldn't be an issue or factor when warm during the summer. Maybe that wasn't accurate?

I can make arrangements to go into the valley to get this reconnected and resolved properly if need be. I had just been holding off after hearing of the job not being very nice. What do you all think?

[David T]

Is there a way to test if the O2 sensor is faulty or not? Mine was replaced about five years ago I would guess.

I can access the connector on the end of the sensor wire itself or I can access where those wires come in to meet the ECU connector behind the driver's seat.

I have a jumper in the back of my ECU right now and I wonder if it has affected this? It went in originally because my idle got stuck high, like 1,500 or 2,000 RPM high. The conclusion at the time was that the thermistor electrical connection had come undone. This is within the valley of the engine and a PITA to get at to reconnect. I put a jumper in on the back of the left side ECU connector such that the two wires that would go to the thermistor and back were jumpered directly to each other and then for those other two wires (that connector has four wires total) I made short jumpers just to sort of reconnect the connector and leave those unaffected. I can post a picture of what I mean if it isn't clear. The thought was that the thermistor was only needed during cold temperatures and wouldn't be an issue or factor when warm during the summer. Maybe that wasn't accurate?

I can make arrangements to go into the valley to get this reconnected and resolved properly if need be. I had just been holding off after hearing of the job not being very nice. What do you all think?

Yes, there is! Refer to D:04:15. You disconnect the wire to the O2 sensor and you should see a steady reading of 40-50 and then hook a 1.5 volt battery to the wire and ground and you should see 20 steady. Trip the WOT switch and you should get 50-60. Ground the wire and you get 87 minimum. If the O2 sensor is over 30,000 miles or 30 years old it should be replaced. When replacing the O2 sensor you are supposed to check and if necessary adjust the valves and then reset the Lambda counter.

[Bitsyncmaster]

Yes, there is! Refer to D:04:15. You disconnect the wire to the O2 sensor and you should see a steady reading of 40-50 and then hook a 1.5 volt battery to the wire and ground and you should see 20 steady. Trip the WOT switch and you should get 50-60. Ground the wire and you get 87 minimum. If the O2 sensor is over 30,000 miles or 30 years old it should be replaced. When replacing the O2 sensor you are supposed to check and if necessary adjust the valves and then reset the Lambda counter.

That does not check the O2 sensor. It checks the lambda ECU.

An O2 sensor can go bad if the mixture was running to rich. It also can go bad if you use non-sensor save RTV on engine parts.

Your jumper on the idle ECU will not affect the lambda system. The lambda ECU is the silver box mouned vertical behind the driver seat.

[David T]

That does not check the O2 sensor. It checks the lambda ECU.

An O2 sensor can go bad if the mixture was running to rich. It also can go bad if you use non-sensor save RTV on engine parts.

Your jumper on the idle ECU will not affect the lambda system. The lambda ECU is the silver box mouned vertical behind the driver seat.

While you are correct this doesn't test the O2 sensor directly, if the Lambda system can do all of these tests and doesn't go into closed loop when you hook the O2 sensor back up, it is a pretty good bet the O2 sensor is bad.

[Jonathan]

Ok, dwell measurement take 2.

Up until late last night, I couldn't have ever told you what a frequency valve buzzing actually sounds like. Not sure mine had ever buzzed before. I looked it over and inspected the electrical connector. I ensured the female end of the pins inside the connector were tight and what do you know, it started buzzing next time I started the car.

It was too dark to hook the dwell meter back up last night, so I just recorded this video this morning. I started the car from cold and missed about the first minute on film (video?? lol). I only caught it in the first second of the video, but for that first minute, the dwell needle was constant, but at a higher value than before. Then right when I started recording, it came down to where it had been. I edited out after the first minute shown here and removed about 1:30 of real time. At about 1:15 in the video (or around 3:45 of real time since the car was turned on), the needle started swinging like mentioned it should.

Have a look. It seems it is swinging in too wide of a range and also gets too low. You can see or hear that correspond to the engine RPMs getting low enough to almost stumble and then go back up. Then it repeats. I shut the car off at the end of this video, maybe 6 minutes of total idling time. It was not up to full engine temp by then.

I can repeat the measurement to see what it looks like with a fully warm engine if that's recommended. What does my needle swinging low like this indicate? Any suggestions on what to check next or adjust next? Thx.


https://www.youtube.com/watch?v=9GMRd_Re7yI

[Bitsyncmaster]

Try bumping the idle up to 1500 to 2000 RPM and then adjust the mixture. You can adjust the curb idle screw or put a shim under the screw to hold the throttle open a little.

The problem with non-heated O2 sensors is at low idle RPM they may get to cold to work. So adjusting the mixture to the correct value (with higher RPM) may fix that idle hunt your getting as it warms up.