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.

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[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?