Rough Idle

[rseeley]

I have a '91 with 248k. When I bought it last year, it had a very rough idle when cold. I replaced the IAC and it solved the problem.
Recently the problem has come back. When cold it will not idle. When warm it idles at about 500rpm and sometimes stalls out. When I give it gas, it runs strong and smooth.
Fuel filter, plugs and wires all changed last year.
I have checked the IAC again, and it is working.
From what I have read, it sounds like it could be the O2 sensor.
Does this sound like a good place to start?
Thanks in advance for any suggestions.
Rob

 

[MrShorty]

I think it might just be the IAC (and at that age the entire upper intake manifold and throttle body) are getting dirty.

 

[rseeley]

I have a friend who works for Napa and yesterday he gave me a new IAC to try. I put it on and there was no change.
I cleaned the throttle body last year. Could it need it again?
The rough idle started pretty abruptly. It started right after I filled up with gas. I thought I had gotten a bad tank of gas, but that was not the case. I put in dry gas and then injector cleaner - no change. I then filled up with high octane- still no change.
Any other suggestions?

 

[dogfriend]

check this thread

I think this thread covers almost everything about rough idle.

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