Rough cold start, erratic idle for 1st few seconds...

[stratford_boy]

Have posted on this issue before. Have a 99 malibu, 3.1 L with approx. 330,000 kms on it. Have had the car for 2 years now and put on approx. 60,00 kms. This car has never started good when cold, during any time of the year. (I live in Canada) Upon cranking it over, it would spit and sputter for a couple of seconds before finally catching, then the idle would fluctuate between 800-1000 rpm, eventually settling down.

I always thought it might have had to do with minor oil consumption past the valve seals, causing excessive rich condition after sitting awhile. I came to this explanation after having checked every damn sensor and module on the thing, fuel pressure, tune up parts and anything else I could think of, never finding any issues. Being an automotive tech, I have a hand up when it comes to diagnostics...

I think I found a repair for this issue:

Using a scan tool, I adjusted the throttle stop further open until the IAC motor steps stayed at 10 steps on a hot idle.

Ever since, my issue is gone and it starts like a 3.1 should, crisp and quick with no idle hunting! It's been 2 weeks now and still good.

Saw at least 1 other person on here about a year ago that had the same issue...if you're still here, try it, it worked for me!

Anybody else that has input, it would be welcome, please reply.

Thanks, Mark

[Imcgyver]

Hello I have the same problem with my 99 3.1 and my scan tool does not have IAC step, any other way to set the idle to produce the same IAC setting?
Thank you for your time and response
Ron

[manicmechanix]

Good tip. Also sometimes cleaning the throttle body helps starting.

[Scott Dunn]

Any idea on how much this would cost to have a garage do it? My 2000 is doing the same, but I have to hold my foot down slightly until the car is warm enough to hold its own.