# Crazy fast idle?



## turbinepowered (Mar 19, 2007)

So, had an occasion to take the new-to-me Quantum 2-door past 4k RPM on the way to work. Discovered power I didn't know the transplanted 1.6 had, but now I have a problem.
Previously, the idle was ~900 rpm. After my little excursion into the upper range, it seems to want to idle at twice that, between 1800 and 2000 RPM.
Fuel system is CIS basic, no electronics, but it does have an idle stabilizer at least plumbed in. Tried pinching that hose off to no change at all, and none of the throttle body screws seem to have moved, or at least none of them feel loose enough to have moved themselves.
Not quite sure how the event and the condition are related, but then it is rather late for me... Appreciate any hints folks can give me to send me back to the wonderful land of lower idle. I really don't want to just start turning screws and masking the problem.


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## turbinepowered (Mar 19, 2007)

Pulled the plug on the bypass valve (that shuts it, correct?) with no change in idle.
Thinking I might have something stuck in one of the butterflies, I pulled the intake boot off and felt around them with my finger. The two sit practically flat, I couldn't feel a perceptible difference or opening around the edges that would allow more air in.
Top of the air metering plate was covered in an oil-like brown substance. Going to try gently cleaning that off of there tomorrow afternoon.
Any suggestions as to why this would just suddenly crank it's idle up like that?


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## turbinepowered (Mar 19, 2007)

Sitting overnight brought the idle back down on its own to ~1200RPM when cold. Once it warmed up the idle settled around 1500.
A jaunt on the highway (65-70mph, 2000-3000 RPM with shifts up to 4k) brought the idle up once more to 1800-2k.
The way I see it, obviously the engine is ingesting more than the usual amount of metered air. It has to be metered, because an idle isn't going to increase due to sucking in extra air; there must be fuel to go with that extra air, right?
So, there are three ways I can think of to get metered air into the engine. The idle bypass passage in the throttle body, past the butterfly valves themselves, and the idle stabilizer valve.
Assuming that there aren't other ways, and assuming that pulling the plug on the stabilizer valve closes the valve, then I'm left with the throttle body passages letting extra air through. Feeler check tells me that the butterflies are completely closed @ idle position, so I guess it really is time to start messing with the idle screw.


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## Longitudinal (Nov 13, 2004)

Kurt, sounds like the idle bypass screw (the little brass one that is hard to get a screwdriver into because of the intake boot) is backing out. Turn that back in. If your idle returns to where you want it, you should pull that screw and replace the o-ring or seal/goo it up with some weatherstrip adhesive or the like.


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## turbinepowered (Mar 19, 2007)

*Re: (Longitudinal)*


_Quote, originally posted by *Longitudinal* »_Kurt, sounds like the idle bypass screw (the little brass one that is hard to get a screwdriver into because of the intake boot) is backing out. Turn that back in. If your idle returns to where you want it, you should pull that screw and replace the o-ring or seal/goo it up with some weatherstrip adhesive or the like. 

Sure enough, the process of elimination and suggestion has brought me to that very same screw. _Loose_








Tighten it down a full turn and a half (using a 1/4" flathead bit and a matching 1/4" box end wrench with a bit of magnetic tape to hold them together







) and the idle obediently dropped to an indicated 900 RPM.
Need to pull that screw, I suppose. Little baby drip of blue loctite would probably be a bad idea, wouldn't it?


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## Longitudinal (Nov 13, 2004)

*Re: (turbinepowered)*

Yeah, not a bad idea. Those o-rings dry up and harden after a while, and this car is 27 years old now! The best solution would be to buy a viton replacement o-ring, but some blue will keep it from backing out. Really, what you want here is not to lock the screw but to add friction. Blue should do that, but that is why I mentioned weatherstrip adhesive.


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