Last night I installed a new A/C Delco IAC. But instead of the car idleing low (at or below 500rpm) it now idles 200-300rpm higher of where it should. The scanner showed that the idle should be 550rpm in gear and 680rpm (IIRC) in Park.

I cleaned the TB very well, including the ports for the IAC, and cleaned the MAF. I cleaned everything from the filter to the TB. The air filter was cleaned about two weeks ago. I also remembered to reset the IAC.

Once all that was done I started the car and let it idle. My scanner showed the the IAC was at 45 counts, the TPS was at .65v and the blades were closed at 0%.

At start-up the RPMs went up to 1500 and started droping to about 1000 and stayed there. As the car warmed the RPMs started comming down. After the RPMs leveled at 1000 the IAC was still reading 45 counts, but started steadly dropping. After about 8min the car was idleing in Park at about 850rpm (never went lower) and in gear the car idled in the lower 700 RPM range. The temp was at 175degrees in closed loop. The IAC count was 0, the TPS was still showing .65v and the blades were closed at 0%. The engine load was at 3%-4% the intire time.

All this leads me to believe there is a vacume leak somewhere, but I checked all the lines on the intake manifold and everything seemed to be OK.

Anyone else have any ideas?

===UPDATE=============================================
This mornig I but a bottle of Lucas Fuel Injector Cleaner in when I filled up with gas, and this evening I changed the fuel filter. Now on startup the RPMs jump to 2K instead of 1500. The IAC counts still drop like a rock, and I don't know if any of this info makes a difference. But hey, the more info I give the better the prognosis I will hopefully get.

 

Yeah, sounds like you could have a small leak.

Is there a gap between the blades and the TB wall?

Have you tried the propane test? (propane near all intake seals/plugs/fittings to see if RPM rises)

If it idled steady above the programed idle speed I'd doubt it'd matter much... but it sounds like its more than just say 100 or 200 above programed. It's staying above 1500?! Has to be a leak there.

 

How's your fuel pressure at idle?

 

Have you reset the IAC? You should probably do that when installing a new one. The computer does not know the pintle position of the new valve. It only knows what the old one was.