93 3.o missing at idle

[chad]

I was told today to look for a vacuum leak. Apparently, because the truck misses at idle but runs fine under acceleration (as the throttle plate opens), a vacuum leak could cause a miss on that cylinder? I know I had the stuck injector problem, which has been replaced. Could it be a vacuum problem causes the miss that is still present?

 

[Geeshik]

Yes, a vacuum leak could cause that.

Spray some Electronics cleaner or other plastic safe solvent around the intake and vacuum lines. If the engine revs up or starts to run differently, you can use this to pinpoint where a leak might be.

More likely though, you have a dirty Idle Air Control. If you don't find an obvious vacuum leak, try removing it, cleaning it, and lightly re-lubing. Note: you may need a gasket when you remove it.

 

[chad]

That sure is a lot easier than pulling the head! I will try that hopefully this evening. I was also told about the IAC by a friend of a friend who is a mechanic. The procedure for testing and replacement is in the Haynes manual. Thanks again, this is turning into a head scratcher, especially for a novice such as myself.

 

[chad]

IAC tested good and no notable vacuum leak.... off with it's head! This weekend we will pull it and see just what the hell is going on. Leaning towards an exhaust valve now, keeping my fingers crossed the washout did not damage the piston or cylinder......