High idle with surge ??

[dg463]

Replaced all my injectors on my 91 ZR1 with Accels and replaced ignition coils, ran great for a few weeks but now when i crank it up it goes to 1200 rpm's and as it warms up the rpm's increase to about 2K, if i turn the car off, the idle goes down to approx 650 rpm's in the tach,which then slowly goes up again as I drive it,I was looking at my ICS valve not sure its stock as it says "made in mexico" with # 0001662768 stamped on the body,I was wondering if this is aftermarket and possible causing me all this grief,if not was is the part # i need to purchase a good quality ICS valve thanks Dennis.

[Racinfan83]

I'm not an expert on this - but my car had a high idle like that and when I had it at Marc's last week he said it was likely caused by the wrong MAP sensor hose. Someone had replaced the original with a piece of hose - which collected oil and wouldn't work right. He replaced with a good piece and my idle is fine now. (He also changed injectors and coils)

[icarus-54]

I had the same problem with my 90.I thought it was a vacuum leak,but that checked out ok.Turns out it was the chip,the original owner never upgraded the chip to the 1616 chip.So I got a chip from Mark and the problem was cured,not to mention the performance increase.

[dg463]

Well I reset the ICS valve and it seems to be idling fine for now idling at 700 rpm,will keep you guys up to date on whats the beast is doing thanks for the input!!

[mike100]

A vacuum hose might have popped off somewhere (possibly under the plenum). After removal of the accordion air duct section, try blocking off the air horn with a very stiff binder book or very thick cardboard etc. If the engine doesn't stall or seriously complain, you can pretty much be assured of too much air getting in somewhere. You might even be able to hear the leak with the intake blocked.

[scottfab]

Well I reset the ICS valve and it seems to be idling fine for now idling at 700 rpm,will keep you guys up to date on whats the beast is doing thanks for the input!!

Not sure what resetting the ICS valve is but....
If the issue comes back try this sequence to isolate:

1. Punch the throttle a bit and see if the idle comes down.
If it does then you've got the TB blades sticking a bit. Take the bellows off and drive the car to see if it will idle high again. If it does the reach in with you finger tip and push shut the TB blades. If the idle comes down put some axle grease on your finger tip and reach in and put some on the edges of the blades. If it did not come down when pushing on the blades take the IAC out and clean out the passages in the TB then clean the IAC but DON'T wipe off all the special grease that is on it. The IAC and the edges of the TB blades came with that special grease and many "clean" too much of it all off. Mistake.

2. If the above was not helpful next time then you've got an intermittent vacuum leak OR more probably the well know oil in the MAP sensor hose issue. Clean out the hose and position it at such an angle that the condensing oil runs down away from the MAP sensor. Just cleaning out the hose or replacing it is only a temp fix.
Good Luck