Rough engine idle, 3.1 Multi-Port.

[LUMINATOR]

My 90 Lumina seems to be running rough when it is idling. I changed the spark plugs and wires not to long a go, AC Del-co spark plugs gaped at .45. Is there any sensors I could clean or replace that would smooth it out? Any advise would be helpful.

Thank you!

[95LQ1VERT]

I would check for vacuum leaks, clean the IAC valve and replace the fuel filter, Its a good start.

 

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[LUMINATOR]

Could I clean the IAC with brake cleaner?

[jman093]

Carb / throttle body cleaner would be better. I'm also guessing it's a vacuum leak though.

[LUMINATOR]

Where could I check for vacuum leaks?

[jman093]

Engine gaskets, any vacuum hose, and any object connected to a vacuum hose. There's vacuum hoses runing all over the engine bay, down to the vacuum resvoir and even around behind the dash inside the car.

 

You can spray carb/tb cleaner around all the gaskets and see if you can get the idle to raise to pinpoint it. You could also try disconnecting all the vacuum hoses one at a time and plugging the nipple to see if it helps idle better and pinpoint the leak.

Edited April 30, 2013 by jman093

[rich_e777]

Check both ends of the large vacuum line going from the UIM or plenum to the brake booster. Maybe clean out your EGR valve and change your O2 sensor. Find your vacuum canister(black ball looking thing maybe found in the fender under the battery) and follow the lines from there, eventually you will come to a plastic joint and these are prone to breaking which will give you a vacuum leak. UIM and LIM gasket failure will give you vacuum leaks as well. The upper is very easy to change, the lower is a bit more in depth but it is worth it once done.