High Idle?

[mtownfiero]

Ok so while i had the top part of the tb off i moved the iac pintle to fully extended so that it blocked off the part it sits in after i had cleaned out the bore and the pintle. With the iac unplugged it still started. My problem is im having a very hard time figuring out what the leak would be coming from.

[Sonyman]

from my experience, the rubber edge on one of the lower intake manifold gasket that sits over one of the intake ports had peeled off causing my engine to rev up. I replaced it and that my high idle went away.

[mtownfiero]

Was the gasket new when that happened? From the lim up was just recently assembled with new gaskets and tq.d to spec. Im thinking part of my problem could be that i didnt do a great job sealing up one of the ports on the bottom of the uim and that could be leaking? What im wondering though is it i took off the uim now would i have to get new uim gaskets again? The motor hasnt had maybe even 10mins of running time since the new gaskets.

[Sonyman]

i'd say about 3 months new but the bottom line is, if your high idle is caused by a vacuum leak, then it has to come from a vacuum line, upper or lower intake manifold gasket or faulty idle air control valve or even your tubing linked to your cruise control. When faced with problems like this, i try to look at it as a human body starting from the throttle body down to the intake valve and figure out anywhere in between...if you see my point. Just think it through.

[mtownfiero]

Im assuming since it is a swap that it is being caused by a vaccum leak more than anything and the more i think about it i really didnt do the greatest job sealing the port on the bottom side of the uim. Problem is i cant see it to tell weather or not its leaking. Im just wondering before i go and take the uim off again if it would be okay to reuse the uim gaskets when i reinstall it or oder new ones use rtv etc..

[55trucker]

You CAN find a vacuum leak by using a propane bottle. With the engine running, open the valve of the bottle (do not light the flame...that will cause unhappiness)...you don't need to have the bottle open very much. Now, direct the nozzle around to the various flanges where gaskets are, vacuum lines are and such (try to avoid blowing directly on electrical items). If you come across a location where propane is sucked into the engine you should hear a change in engine rpm. Voila ...you've found a vacuum leak.

[mtownfiero]

By propane tank you mean like a grill style propane tank lol. Im guessing by rpn change you mean that its going to go way up like if nitrous were introduced.

But back to the other question i had, if i removed the uim to reseal the port on the bottom of the uim would i be able to reuse the gaskets?

[55trucker]

Well....I was actually thinking of a small handheld cylinder with a nozzle on the top that you light. I've never personally tried to reuse the plenum gaskets even if they were relatively new (since they are not expensive I've just replaced them) once compressed, they are compressed.

[mtownfiero]

Alright thanks ill try the propane thing next and see what happens.

[x-thumpr-x]

Does your fiero have cruise control and the vacumn lines hooked up to it? The black canister under the actuator are known to rot out and cause vacumn leaks. Also a stuck EGR valve can cause this too. If you EGR valve has an open bottom style, carefully try pressing the lower diaphram up with your figures and see if it moves freely.