Fast idle warm 1981 Spider FI

[deang]

I've read and tried everything I can think, read the forum, read the tune up info and still the car idles around 1500rpm when warm. Actually, it starts to increase a clue of minutes after a cold start. Currently have the brake booster hose and the auxiliary valve plugged. I can't find any vacuum leaks. Nothing is cracked. Idles screw all the way in. I just don't k ow where else to look. Anyone got any ideas? It idles smoothly and drives very well.

[wizard124]

Two other vacuum lines to check: vapor canister and vacuum advance to the distributor.
Throttle plate closed?
Leaky CSV? Pinch off that fuel line to see if it affects idle.

[vandor]

Likely someone adjusted the idle via the throttle plate adjusting screw, so it does not close all the way.

[KevAndAndi]

Did you replace the idle speed screw's o-ring? Or is it in good shape? Basic, I know, but just checking.

[76was124]

I've read and tried everything I can think, read the forum, read the tune up info and still the car idles around 1500rpm when warm. Actually, it starts to increase a clue of minutes after a cold start. Currently have the brake booster hose and the auxiliary valve plugged. I can't find any vacuum leaks. Nothing is cracked. Idles screw all the way in. I just don't k ow where else to look. Anyone got any ideas? It idles smoothly and drives very well.

I feel your pain....I have been struggling with the same thing since last Fall. I finally settled on a compromise between too low an idle at cold start and too high when fully up to temperature. Right now my car idles around 900 when cold, and about 1200 when fully warm.

My gut feel tells me its a worn track on the AFM...but decided I was just going to enjoy driving it as is without having to put it in neutral and rev it at stop lights when barely warm to keep it from stalling. ( just after Aux Air Valve closed)

This was after ruling out any air leaks, incorrectly set throttle plate, idle screw, throttle position switch (TPS) and replacing the temp sensor and the AUX air valve ( AAV/AAR ) with no imporivement.

[bradartigue]

I would guess you both have throttle plates that won't close all the way...the AFM is too stupid a device to force the engine up 300 or 400 RPM, or else you have air coming in from somewhere. If the throttle plate isn't closing right then you have a system that is legitimately drawing more air.

If you unscrew the throttle set screw completely and close the idle adjustment screw completely does the car stop running? It should, or damn near stop. If it is still running at above, say, 500 RPM, and you're certain no air is coming in from elsewhere then the air is coming in from the throttle itself, through the AFM. This doesn't mean the AFM is defective, but that your throttle isn't closing fully.

[76was124]

...but that your throttle isn't closing fully.

Good Point Brad....I re-read the Original Post and missed that he had his idle screw all the way in and was still at 1500 RPM, so what you, Vandor and KevinandAndi said makes sense for Deang.

Mine is a different issue as I can stall it with the idles screw all the way in, as the idle drops below 500 the dual relay starts dropping out.

[deang]

Thanks all. Previous owner had rotated the throttle switch all the way and that kept the throttle plate open just a wee bit. With that fixed I had very low idle cold and 800-900 rpm warm. Found the auxiliary air valve not opening. Inside the small arm that's suppose to push against the bimteal piece broken off so the valve not opening when cold. Now I'm just looking for a replacement. It looks like a '80's VW Rabiit/Jetta part is the same and I might be able to get one today. Thanks again.

[bradartigue]

...but that your throttle isn't closing fully.

Good Point Brad....I re-read the Original Post and missed that he had his idle screw all the way in and was still at 1500 RPM, so what you, Vandor and KevinandAndi said makes sense for Deang.

Mine is a different issue as I can stall it with the idles screw all the way in, as the idle drops below 500 the dual relay starts dropping out.

Your relay starts clicking because the demand for air gets so low the flap is fluttering and the pump is going on and off. The dual relay turn on the fuel pump when the AFM door opens (that's 1/2 of the "dual" part). If you can adjust the idle speed to that point and you can't bring it up to 850 then you have some extra air coming in there. Is the little hat on your emissions canister vent? Is your distributor vacuum capsule leaking (it can screw up an idle if it is broken because air flows right through it into the plenum).

[76was124]

If you can adjust the idle speed to that point and you can't bring it up to 850 then you have some extra air coming in there. Is the little hat on your emissions canister vent? Is your distributor vacuum capsule leaking (it can screw up an idle if it is broken because air flows right through it into the plenum).

I don't want to hijack this thread, so my issue previously posted under:
http://www.fiatspider.com/f08/viewtopic.php?f=5&t=30235

But short answer, I can bring it up with the idle screw, which is what I did but basically idle climbs as it warms up and if I turn the idle down when fully warm to 950 RPM. Then it's too low after AAV closes and before fully warm.

No air leaks I can find with propane. I had already replaced the distributor vacuum advance diaphragm as it was torn. New AAV as it was leaking through the case, and new temp sensor, as it was out of range.