Ok, just got done installing my H/C. Had my PCM tuned by PCM4less which set my idle speed at 850rpms. Car will idle at 850rpm or close to it on a cold start. Once warmed up it idles around 1200rpm. PCM4less said it could be a TPS sensor, vacuum leak or exhaust leak.

I checked the TPS and the volts appear to be all good .700v with TB closed and 4.76 WOT between the blue and black wires. Im also getting 5v on the gray wire.

I can't find any exhaust leaks so that leave me with possible vacuum leaks. But what about the IAC valve? Could that also cause a high idle? In the mean time ill try to find any vaccum leaks. Thanks for any help!

 

The IAC is going to react to whether or not you have a vacuum leak. I'd check for leaks, first, then try to get some scan data on the IAC counts. Is the TB still currently stock?

 

Thanks for taking time to respond shoe. The TB is not original, its a 58mm BBK. I have an appointment on thursday at the dealership down the road who will do a smoke test on the car to check for leaks so hopefully since the H/C install i don't end up having a dozen of them.

If there are no leaks, would the logical next possible problem be the IAC since the TPS checks out good? Ill see if i can get the dealership to read the count on the AIC if they don't charge me an extra fee, they are already carging me $95 for the smoke test.

 

my iac recently went bad. It would high idle quite a bit but was very inconsistant(sometimes was decent and sometimes over 1500rpm). The counts were all over the place. It got bad enough I didnt drive car until I got the new one in. I would confirm the throttle is closed(both by hand pushing linkage and visual inspection that blades are closed. A vacuum leak should be consistant and not idle down. Im not sure if a vacuum leak would not appear in the cold start condition(others would know that and what line or area to look at.) The pcm also keeps track of the iac counts and kind of learns so resetting might cause a change as it would go back to thirtyish rather than what it has learned since last battery disconect or pcm fuse pull. There is also a setting of the iac by starting part throttle and running a few seconds the turning off and waiting about ten seconds and starting. Shoebox has that info. You can also test the coils resistance on the iac with ohm meter. Is the tb a new addition with the h/c? I did a couple of the tb mods that helped my situation out( more of split blm and high iac count but my iac was dieing).


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Your BBK TB could be the issue. There are things that have to be done to set up an aftermarket TB. That is going to include some time with a scanner to look at TPS and IAC data. It would be a good idea for you to have the ability to look at those things.

 

Thanks Rob and to all that have replied. I just got done with the smoke test and there were no "visible" vacuum leaks. The tech said my tach was off because there computer when hooked up showed my car idling in the 800rpm range while my tach showed it running 1,100rpm or more. I have an auto meter tach I had for my 6spd I use to have, never installed it on my auto car I'm referencing here because I always felt it was taboo to have a tach on an auto but it looks like it going to be needed.

 

I think the majority of our cars are off on the tach but not quite the 300 yours shows. From what ive seen many are in the 150-200 off range including mine. Did they give you your current iac counts and what the current memory is? If you can afford a cable and some data monitering or logging software you may pay for it in throwing unneeded parts on and fine tuning your throttle body as well as any future needs. The problem with your throttle body is it doesnt use the iac passages it just dumps the air behind the blades and some of the cyllinders hog that air while others starve often creating a bad split in blms. One of the mods forces the iac air to go into the iac passages like the stock tb does(it either uses a brass tube or a filler in the throttle body were the opening dump into the plenum. If you still have your stock tb its helpful to compare but their are also pictures showing both the mods and the stock tb. The other big difference is a through hole on the stock tb that bypasses the iac valve(roughly a 3/32 hole). Adding and or adjusting that hole size is also one of the mods and that one is used to get the iac counts around 30 or so. Like I said you can test the resistance in the coils of the iac valve. Mine tested fine but valve was probably damaged when I switched it from my stock tb to my current one. You can damage them by improper handleing and cleaning. I shopped around on the one I bought and found a delphi for about 70 bucks vs the 160 the local dealer quoted so if you end up needing one thats the price spread. First thing first check the blades being closed and the linkage against the stop screw(this one is best done when its high idleing). Currently mine will often stick just a little(worth about 100 rpm) and a bump of the throttle will get it down.


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haha reread your original post. thats interesting because your idle may be right or very close warm and super low cold then. Or your tach is super wack.


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Thanks for the post tho it was a good read and very well written. I had my car on two separate scanners today, once at the dealership and again at a performance shop and both showed my idle in the 800's just as it is tuned to be so yes....my tach on my dash is way off. Its not the original dash, I took my 96 dash out and installed a 97 dash so i could have the digital odometer, that perhaps could be part of the problem. Ill install the auto meter tach that i have. I never did it before because i though guys with automatics got laughed at for having aftermarket tachs but ill remove the shift light and use it to monitor the actual rpms, at least that way in the future if i have idling issues ill know for sure since ill have a true gauge for the rpms displayed on my A/M gauge.