87 Tbi 350 rough idle in gear

[firebird]

Blew the vacuum line off the MAP sensor the other day driving home and after finding and fixing it I decided I'd address my noisy rockers. I set all the valve lash to 0 then 1/2 turn with the motor running and it sounded better. I then drove the truck and idle drops down lower now when in gear and knocks.

Runs like a top in park. Is the MAP sensor still sorting itself out? Why'd my RPM change in gear now? Have I got a different vacuum leak?


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[Georgeb]

You can try resetting your IAC and search for another leak with carb cleaner. What is your ignition timing at?

 

[firebird]

IAC was my next thing to check. I'm waiting for a buddy to check my timing while in gear. I'll clean IAC and see if it improves. What would have caused the line to blow off the MAP sensor? It wasn't under heavy acceleration or load.


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[Georgeb]

I would set the ignition timing at 12 deg advanced in park and the IAC to its base setting. I would think a vaccume leak would cause a high idle condition. Regardint the map sensor hose. A good intake backfire could possibly do it. Is that line in good shape and nice and tight? If it is one of those plastic lines with the rubber ends it may be leaking or fit loosely. Toss that thing and replace it with standard vacuume hose.
You may also want to check if the EGR is closed at idle. It should not have vacuume to it at idle.

 

[firebird]

I was away a few days.

George- Yes it is a plastic line and rubber ends.

The IAC was broke right where the threads meet the main body. Just went to take it out and it broke as I was putting the wrench on it. Going to have to get the rest threaded out of the throttle body.


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[firebird]

Got a new IAC. Old one was rusted and gummed up. Run a can of combustion chamber cleaner through it. Running fine now