Rough idle when cold - things to check?
 

Just replaced all the vacc. lines and installed a new ISV (works much better!) Car runs like a top right now except when starting the engine COLD, it'll idle at about 500 RPM, which is kind of rough (things vibrate and shake). Once warmed up it's balls-on 840 RPM. Thoughts on things to check?

Found this in a search. Did you ever resolve this one?
Mine is the same, but will NOT idle when cold, but once warm it is trying the 300 RPM idle like yours when cold. Kind of like a lower RPM version. So maybe it is the same problem just different settings, etc..

I have the same problem, anyone have any ideas on this problem? Mine cropped up after a vacuum line change and venturi delete.

Ok that is three for sure with simular problems. Someone here has HAD to have found some kind of solution. Maybe just a better place to start looking for the problem? I have checked my Vac. lines and looked at the connections for the sensors, but nothing has worked yet. :confused: Will maybe try the AAV next week. God, I don't want to remove the intake... :crying:

Well make it four guys. I have the same problem... rough idle till warm and then its fine... but mine also runs really weird until it warms up WITH gas. It's almost like the fuel stops coming in just for a second... almost like a mis... or a sensor. So yes, someone please help.

Add me to the list..........car idles rough then there is a sudden small surge in rpms and then idles smoothly.

If you already replaced the ISV and the vac lines, how about the boot to the AFM? They get hard with age and even if it isn't torn it may not fit with a tight seal any longer.

How about this, flapper in AFM may be gummed up with oil mist maybe? So it kind of sticks until the engine bay warms up? I'm grasping at straws with that one?

Interesting. . .

Four guys and at least two of 'em (myself included) have done the venturi delete.

For one, I thought the car was supposed to idle slightly higher-than-normal when cold to assist with warm-up, but I could be wrong about this.

What chips are you guys running? I may throw my stockers back in just to see if that solves it.

Stock Chip and I did not do the Venturi delete either. Just checked the vac lines. The boot on mine seems to fit well and as far as leaks there are no apparent ones. Mine also will idle when warm, just at 300 rpm while cold it will die as soon as I stop supplying fuel (throttle). :crying:
I would like to see if your chip swap will help. Maybe it will give the rest of us a place to start.
:thumbsup:
Higher idle at cold is what I thought too. Every other car I have seen is this way.

It seems like all of us aren't from super-cold climates either. . .

How many have checked as per WM/Clark's:

Pressure test intake sys?
Check fuel pressure?
Adjust idle?

Put me down on the list. Mine wont really idle unless I give her gas and warm her up. I am in the cold climate of the windy city. She gets pretty cold here. Mine had a chip too from Euro something. Go Bears!!!!

I'm from a cold climate. Mine used to surge up and down from almost stalling to about 1000 right after startup when it was really cold out until the engine got up to temperature, then it would settle down to normal idle. Unfortunately I can't say what fixed it since I replaced most everything when it was warm out, including the boot which was so hard it wouldn't stay on the AFM very well any longer, vac lines and ISV.

When cold, my car idles very rough, but at about 900 rpm. Then after a few minutes, when warmer, it just suddenly smoothes out, also accompanied by what feels like a surge. I was thinking a head gasket problem but am not convinced, since temp remains normal, minimal coolant loss. Don't think it is ISV since idle is fine. (even when running rough).

Try cleaning the connector to the airflow meter. Worked for me on the S2.

Also check the infamous DME relay. I had a problem starting the 951 which was solved with a $25 relay that worked like a charm. The date on my old one was Oct 1990! The old relay has been superseded by a larger unit with a 993 extension in the part number (993.615.227.00).

Good luck and let us know what you find.