Idle issues and codes.

[87hurricane]

I recently purchased a SHO, guy that I bought it from told me that a 60K had just been performed, and it appears that it was. The car runs fine, but it doesn't idle very smooth, and now that its getting cold, I'm having cold startup issues. Plugs and wires are brand new, cleaned the MAF and TB. When the car is warm it runs fine, although the idle is a little rough, stumbles occasionally, and idles at about 1000rpms. The guy I bought the car from told me he replaced the IAC valve, and it looks new. When the car sits overnight in the cold, it won't idle, it will start, then stall. If I give it some gas, it will continue to run, and after holding the idle at 1500 for a min or two, it will idle without stalling, but its rough until it warms up. Pulled the codes this morning, and I am getting a 411 code, which points to the IAC. Anything else I should look for before I replace it? Oh yeah, someone definitely moved the base idle screw....I think I've got it close, but is there an actual procedure to set the base idle screw? Thanks in advance guys.

 

[johndallara]

my '95 ATX also has done something similar for quite some time. I had replaced the IAC with some improvement in the problem.

Although I never got a code for it, at some point I wondered whether the air temp sensor (airbox) or the coolant temp sensor (engine block) might be bad. Both checked out OK. I got some improvement in the problem by replacing the coolant temp sensor -- this made sense to me.

Cleaning the MAF -- you did this already. Anything else that would effect cold start drive-away would potentially be suspect. I have even wondered whether my computer might have a failed component which accounts for this.

Best of luck, would be interested in hearing what others have to say.
JD

 

[87hurricane]

Update: Idle problem is fixed...mostly. I pulled the TB off to find that someone had put the gasket on backwards, and the gasket was blocking the port that runs to the IAC. New gasket in place, and the car idles better, and starts much better in the cold. Idle still isn't as smooth as I think it should be, but its much better. Car isn't showing any codes now, and it passed the balance test, so I'm not going to worry about it for now.

 

[johndallara]

idle issues

good work.
JD