High idle with 22 inch of vacuum

[skylark]

Check the timing. If it is too far advanced it will bring the rpm up. Perhaps someone else can answer this @someotherguy comes to mind, the 88-91 has an ESC module. I know that it effects the timing but I don't recall how.

 

[Chewy1576]

Check the timing. If it is too far advanced it will bring the rpm up. Perhaps someone else can answer this @someotherguy comes to mind, the 88-91 has an ESC module. I know that it effects the timing but I don't recall how.

Isn’t the ESC module for the knock sensor? I know that the 94-95 later model PCMs have that circuitry built in so it doesn’t need the ESC. Knock sensor is wired directly to the PCM.


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[redfishsc]

There's a part of me that still wants to say you got a vacuum leak of some sort going on. Next time you're having the high idle problem, try using a set of channel locks to pinch off your brake booster hose. If blocking some of the flow from that brake booster hose changes your idle RPM, you may have found your culprit

 

[77Impala]

I will check both the timing and pinch off the brake booster hose and see what that does.

I am starting to suspicion a problem with the wiring bundle on the drivers side of the engine block. Saturday I found the area of the engine harness that has a heat shield wrap near where the air-pump feed line to the exhaust manifold was touching. This morning I pulled the harness away from and zip tied the harness where it would not touch anything metal. On todays drive the idle rpms did not higher than 1400 rpms. I am thinking there maybe a few melted wires in the harness. I will find out this weekend.

 

[77Impala]

After a long day of pulling parts to change the intake gasket I found the actual problem. The MAP sensor elbow that connects to the throttle body. Found a crack in it that also had dirt in the crack which told me it was a old crack. I had tried to pull it a month and a half ago but it would not come off the throttle body. That explained the random high idle problem that it had. Did not continue to change the gasket

So far it idles at around 700 rpms when warmed up.

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