Yup another idle problem question

[AirmanPika]

I can't quite find any thread that helps me narrow down the issue so I wanted to ask instead of spinning through ideas when there might be an easy solution.

I drove the car from Ohio to Colorado with no issues back at the end of Nov and it's been in my garage since as I haven't had time to get it out to drive again. I did start it a few times and I feel like at least the first couple months it had no idle issues.

Now...not matter cold or hot, standing still or being driven, if you take your foot off the gas and let it go immediately to idle (775rpm) it dies. I was hoping that getting it out on the road would work out the problem in case it was just unhappy from sitting but that didn't help.

If I am VERY careful and SLOWLY let off the gas once I've gotten it down to idle speed it will idle no problem and stick there happily. Obviously this isn't an option if you are out driving at lower speeds and have to shift or stop at a light.

ISM seems to be buzzing along fine, the fact that it can idle doing the above says no apparent vacuum leaks, and I've done utterly nothing to the car between the time I got it here and now.

Since it's easy to adjust I did do a quick attempt at adjusting my CO (seeing as I'm at a higher altitude) but that had no impact and I set it back to where I had it.

Any thoughts?

[dmcnc]

How did you adjust the CO? What tools that you use and what parameters?


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[Michael]

You will want to check the basics like loose or broken vacuum lines, especially around the dist. advance solenoid. Make sure your wiring attached too. Look at the CPR too. Take a look at the microswitch and make sure the connectors haven't slipped off, and it's still being tripped at the proper time. Maybe stick a multimeter on it and verify it's still good. Also look at your set screws for the plates, maybe one has lost the nut and worked it's way in a little too much.

If it's been sitting for a long time I would put some miles on it and maybe even some fresh gas before really going to town looking any deeper.

[Bitsyncmaster]

Since your idle motor is humming the idle ECU is probably good and connections are good.

My guess would be your idle motor needs cleaning and is sticking.

[AirmanPika]

OK all good places to start. Thanks.

[AirmanPika]

Well I haven't had much time recently to troubleshoot but I came up with a temp solution. As long as I keep the throttle micro switch depressed the car will idle at 750rpm just fine.

Makes me wonder if I need a new O2 sensor.

[DaraSue]

I was having a similar issue (also after a road trip) and it was a combination of warm-up regulator (replaced by my local mechanic, slight improvement but still idled low and rough enough that I felt like it was going to die if I took my foot off the gas for the first couple minutes) and idle speed motor (replaced at DMC MW, had a flaky wire that was making it intermittently cut out). The idle speed motor had been replaced by the seller before I bought it but apparently the newer ones are made in China and more prone to early failure than the Bosch ones so if yours was replaced recently, don't rule that out.

[AirmanPika]

So I haven't gone as far as a total teardown yet but weird thing. I implemented an old fix from way back when and simply disconnected the idle speed switch entirely and all works as it should. Idles perfect, no problems when driving, etc.

I know I need to address the real reason for the issue, but right now I'm basking in the fact I can drive my car again normally.

[Rokkinlen]

Any update? Was it the O2 sensor?

[AirmanPika]

Unfortunately no. I've been using this poor thing as is since. Had other thing come up so never really addressed it.