Cold idle ? for the ECM experts
Thread Starter
Burning Brakes
Joined: Sep 2001
Posts: 1,159
Likes: 73
From: Sumter, SC
Cold idle ? for the ECM experts
I've got an idle at start up problem, so far, new plugs, cleaned TB, performed bypass, new fuel filter, air filter.
After it sets, usually overnight, but at least all day, it starts immediately but idles very rough and acts like it wants to stall. If I leave it alone, it will fix itself after about 15-30 seconds. What I normally do is just immediately turn the ignition switch off, then back on and restart. It then idles perfectly.
This is what I think must be happening, when the car is cold something, switch, sensor, etc.., is sticking. When I first start the car, the ECM reads all the outputs and inputs and does a best reasonable guess as to what needs to happen to make the car idle. Since mine isn't idling correctly under those conditions something is failing or sticking. The reason I think this is because after the intial start when it idles bad, I turn off and on the ignition, the ecm must then be getting the correct inputs, outputs and that's why it makes the corrected adjustments to allow the car to cold idle properly.
I don't think it's the TB, because I removed it and cleaned it really well.
The IAC, was cleaned also, and if it were that, it wouldn't respond so well to the off and on again ignition switch.
Could the MAF, be giving a bad reading at cold start?
No Codes are present, and the SYS light works.
The EGR has been removed, but it did this before I did that.
I've checked all connections with a vaccum pump for leaks, and it's tight.
How does the ECM work on startup, is it time sensitive?
It only happens after the car has set for atleast 10-12 hours.
It is parked in a garage so no moisture and I drive it every day.
Thanks,
After it sets, usually overnight, but at least all day, it starts immediately but idles very rough and acts like it wants to stall. If I leave it alone, it will fix itself after about 15-30 seconds. What I normally do is just immediately turn the ignition switch off, then back on and restart. It then idles perfectly.
This is what I think must be happening, when the car is cold something, switch, sensor, etc.., is sticking. When I first start the car, the ECM reads all the outputs and inputs and does a best reasonable guess as to what needs to happen to make the car idle. Since mine isn't idling correctly under those conditions something is failing or sticking. The reason I think this is because after the intial start when it idles bad, I turn off and on the ignition, the ecm must then be getting the correct inputs, outputs and that's why it makes the corrected adjustments to allow the car to cold idle properly.
I don't think it's the TB, because I removed it and cleaned it really well.
The IAC, was cleaned also, and if it were that, it wouldn't respond so well to the off and on again ignition switch.
Could the MAF, be giving a bad reading at cold start?
No Codes are present, and the SYS light works.
The EGR has been removed, but it did this before I did that.
I've checked all connections with a vaccum pump for leaks, and it's tight.
How does the ECM work on startup, is it time sensitive?
It only happens after the car has set for atleast 10-12 hours.
It is parked in a garage so no moisture and I drive it every day.
Thanks,
Safety Car
Joined: Mar 2000
Posts: 3,620
Likes: 2
From: Hillsboro OR
Re: Cold idle ? for the ECM experts (Curtis629)
Check you battery connections. I had some strange behavior a few week ago and found the postive battery cable was loose. I only discovered this because the car did the click routine one morning.
