240sx- rough idle when started

[aleph1]

Ive searched and found a few related posts, but nothing exactly the same or conclusive.

I have the DOHC engine with 170K miles(ran pretty much fine before, just recently replaced alternator).

Sometimes, mostly after not using my car for more than 15-30 minutes, when I start it up my idle goes between 500-1000rpms and shakes the whole car.

It goes away and idles nomally again after a couple minutes of driving and/or revving high.

I just recently started doing this and I have no idea why. As far as I can see, suggestions for a fix range from spark plug wires to temp control sensor to idle air valve. Anything more specific or anyone have a similar problem with advice?

[Dougster]

I would first check all connections and make sure you also don't have any vacume leaks...I have a situation that might be related in a car I am looking at as well and will be checking back on your problem too..

[aleph1]

I ran some seafoam in my intake, cleared it right up! =)

[NISTECH]

check your coolant temp sensor