Surge at idle when cold

[DanVB1]

Lately, my engine has been surging at bit at idle before fully warm. No codes. Runs well after heat-up. IAC valve?

 

[Earl43P]

Very likely.

Unplug its connector while it's happening, see if there is any change.
No change = bad IAC.

You should also see how it acts with Heat/AC control in the OFF position to rule out normal AC compressor clutch cycling (which affects the idle).

 

[dan's ranger]

I hope I am not hijacking this thread, but I have the exact problem with my 92. I intend to check into the IAC valve.
My question is this, since I don't have a garage and it is cold outside, can I just live with the problem until it warms up this spring, or should I deal with this now? Will the valve go bad and strand me somewhere? It runs and idles great, once the truck warms up a bit, and I can live with this the way it is for a while. p.s. this truck is not a daily driver, just use it 2 or 3 times a week.

Dan

 

[DanVB1]

On my 97, the IAC is as easy as it gets to service – directly on top of the intake manifold. Just remove the plastic linkage cover first by popping out the plastic clips (be careful not to break).
I took mine off to clean this past weekend and after 120K, it was still very clean. There wasn’t any caking or build-up at all. I sprayed some carburetor cleaner into it anyway to remove the light film of carbon.
I have not noticed any improvement in idle since it wasn’t dirty to begin with.
Another word of caution – be careful with the gasket, as it can be brittle. Mine was and I will replace soon.

 

[rurouni20xx]

by all means clean it or change it, mine jumped to 4000 rpm and stayed there going down the road, not good, had to disconnect it and idle w/ my foot at red lights til i could get to autozoo, its a potential safety hazard!

 

[DanVB1]

A new IAC is about $50 - $100, depending on brand and store. I guess it is cheap insurance compared to being stranded. It does not hurt to replace, especiall if the engine has 100K+ miles.