Idling Problems

[j_r_starr]

I just bought my first car -a 1990 Legacy Wagon with 290,000km on it. It seems to be the perfect car for my application (road trips, snowboarding, photography projects outside the city) and I'm stoked to have it. But, it has some issues while it's idling. It will bounce between 500RPM and 1000RPM. When it's running, it's generally fine and really only gets nasty when idling. However, today I had it on cruise and it would fall below the set cruise speed and then crank it up to reach the set cruising speed again.

I changed the oil, air filter, spark plugs and (although it's not related) the coolant, but no change.

Any ideas?

Like I said, it's my first car and I have a decent beginners knowledge of cars and can do my own fluids, filters, plugs, etc., but my knowledge after that is lacking. Any help would be awesome, even if the answer is "get a tune-up". Thanks in advance.

[green97gt]

im not familiar with that generation, but i would look for vacuum leaks. vacuum hose is cheap, so go thru and replace all that, especially with that high mileage.

as well as find and clean your idle air control(IAC). this would effect idle but not cruise. someone will chime in on where it is on that car.

[Custom Import Heads]

Vacuum leaks at the manifold are common. MAF probably needs a good cleaning. IAC valve should be on the throttle body and would benefit from a thorough cleaning as well. Have you done a compression test or leak down? Probably wouldn't be a bad idea to learn the internal condition of the motor.

[impreza_GC8]

Replace vacuum hoses. I just did it on mine and it cost me less than ten dollars in hoses from AutoZone. Also, clean your IACV and replace the gasket. Get a new gasket from the dealer before you take the IACV out, the gasket is NOT supposed to be reused.