New owner, new member! Cold start issue?

[rjd2]

Hi all! New member here. I recently purchased a very solid condition 1983 DMC-12, which I'm very excited about! I will surely be popping in with a few questions here and there. But my first one is this:

The car seems to struggle to maintain a steady idle from cold start. Once stable, it seems to idle right around the 750 mark. I tried to assess the dwell reading; using an Actron meter(which it sounds like may not be the best unit out there!), i was getting a reading of 45.2 at the 8-cyl setting. When I turned the alan wrench at the distributor cap, I got no change in this reading. I could turn it counter clockwise til the engine stalled, and the reading was pegged at 45.2. Should I see an immediate change in that reading upon a slight turn in the alan wrench? Thanks for any help!

PS-I was using these contact points shown in this video:

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

[David T]

Could be a lot of things including dirty fuel injectors, worn spark plugs, bad ignition wires. Might need a good tune-up and/or some vacuum leaks. If it is only a warm-up problem it is often a bad CPR (Control Pressure Regulator). That is what controls the mixture during warm-up. Do not try to adjust the mixture to "fix" things until you know everything else is working correctly.

[Bitsyncmaster]

Is your frequency valve buzzing? The book dwell values assume you have it set to four cylinder range. On 8 cylinder, 45 degrees says your at maximum and it will never go above that value.

[Jonathan]

Yea, that video is a bad example, unfortunately. Not because of the connections, but because it shows the needle stuck in one position, and that's not what it should be doing.

If the needle doesn't fluctuate (like in that video) it means the engine is cold, or the oxygen sensor isn't working, or the oxygen sensor isn't warmed up yet and so isn't working, or some other electrical portion of that Lambda system isn't working, or some random combination of the above.

As Dave said, get it all working before you change the CO mixture, don't start with that adjustment. It is probably your O2 sensor not working, for one reason or another. How many miles are on the car and when was the last time the O2 sensor was changed?

[rjd2]

thanks, everyone. 33k miles, no idea when the O2 sensor was changed. i think it could be at least partially a meter issue; the meter stays pegged at 45 when not connected, and when connected also stays pegged, just at 45.2.


question: to disconnect the CPR, do i need to clamp off any fuel lines? is it pressurized when the car is off? i am planning on swapping this unit out, as it sounds like it is likely the culprit for the cold start issue. thanks!

[Jonathan]

thanks, everyone. 33k miles, no idea when the O2 sensor was changed. i think it could be at least partially a meter issue; the meter stays pegged at 45 when not connected, and when connected also stays pegged, just at 45.2.


question: to disconnect the CPR, do i need to clamp off any fuel lines? is it pressurized when the car is off? i am planning on swapping this unit out, as it sounds like it is likely the culprit for the cold start issue. thanks!

If you came on here to ask questions and get advice, I would continue to do that before you go ahead and replace the CPR. That may very well be the culprit, as you said, but there is too little information thus far for many of us to help you diagnose that at the moment.

33k miles is just beyond the point where the manual says to replace the O2 sensor. That could still be it, or at least part of it anyway.

For the meter issue, I would suggest taking a video, or some photos at least, of the car and meter while you are doing this test and posting here. Often the pictures, or videos, help guys fill in the blanks based on what they see or don't see.

Engine bay pics of a variety of different areas and angles and the fuse and relay area behind the passenger seat would be a good start. The problem could be as simple as you having the wrong electrical connector on the top of the CPR.

[Bitsyncmaster]

thanks, everyone. 33k miles, no idea when the O2 sensor was changed. i think it could be at least partially a meter issue; the meter stays pegged at 45 when not connected, and when connected also stays pegged, just at 45.2.


question: to disconnect the CPR, do i need to clamp off any fuel lines? is it pressurized when the car is off? i am planning on swapping this unit out, as it sounds like it is likely the culprit for the cold start issue. thanks!

That is why I asked if your FV is buzzing. With no power to the lambda system your meter does not show anything. Some meters will read 0 and some read full scale when not connected.

If you still have rest pressure, your CPR lines will spray when you remove them. You can check your rest pressure by lightly tapping the air plate to see if it moves.

[rjd2]

sure thing. hopefully, i can attach photos of the engine here. i'll try to get a video done of the mixture calibration procedure; at the moment, it surely seems to be a lower priority than the start issue.