Hi guys,

My 1995 Camaro LT1/T56 combo transplant in a 1984 Jaguar xj6 is suffering from high idle. It idles at around 1400-1500. I have done the following:

I investigated for an intake leak, and didn't find one -- I replaced the intake gaskets again for good measure and torqued everything down to spec. Still it is idling high.

I replaced the IAC.

I've checked for other intake leaks at the brake booster.

I replaced my MAF.

I tried Re-setting the IAC (holding the accelerator pedal down slightly on startup and then letting go after 5-10 seconds)


I'm not sure what else it could be -- the car threw one code (the fans clicked on, so I decided to check out what the code was) but when I scanned the PCM, there were no trouble codes stored.

Since my Speedo isn't working (i tried solving that one a couple weeks ago) i could have a VSS problem -- does the VSS partially control idle?

I don't know what the problem could be -- does anyone have any suggestions? I feel like i've exhausted all options. One of my friends says it could be that the timing is off, but the engine isn't running rough, just a high idle.

What else could I try? Since the car is a conversion most mechanics are reluctant to work on it, and I've done all the other work on the darn thing I'd like to figure it out on my own, but it's diving me nuts!

Thanks for any help!

 

First off, any mods done to the motor? all stock?. Do you have a way to scan it to check your IAC counts. It could be as simple as adjusting your throttle blades if the IAC counts are off. other than that you would need software to get into the pcm to see if it has been altered...

 

Everything is stock except for a few tweaks like fan temps & I turned off VATS. I looked at throttle blades and they looked ok -- I read that you can't adjust the idle speed with the set screw; is that the adjustment you're talking about?

 

yes, that is not an idle adjustment screw like on a carbed motor, but if your iac is off, adjusting this will help. you will know because if you close the blades and the idle drops but then goes back up, then its not the problem..

 

i seam to be having the same issue i have a 95 firebird v8 and i just replaces the iac valve and it still idles around 1500rpms also when i put it in gear it jumps a bit and idle goes down any tips?to my knowledge the car has no mods.

 

I'd check to see if there is a leak/crack in the tube that goes from the pass side valve cover to the pass side of the throttle body or leak/crack from the PCV tube on the other side.

I'd make sure the throttle is closing all the way against the stop, if it is, then I'd try adjusting the screw so it will shut a little further. If your problem is related to it not shutting all the way or hanging open a bit, a second spring fixes that. If you adjust the screw, it is best if you can see what the IAC controller is doing, but I'd still try adjusting it if nothing else worked.

 

birdnerd

vacuum leaks from old, cracked vac lines and fittings can cause high idle

if your car was running fine and this just started it is not the "stop" screw on TB. That is something that should not be touched from it's factory setting

when you replaced IAC did you also clean out the area it sits in?