JP95ZM6

Ever fix this?

Last time it happened to me, it was a bad TPS connection. Cleaning contacts and new pigtail fixed it. I could play with the throttle and monitor TPS volts, and ocassionally it would jump high or low, and it would hang at high idle. It would do this for the rest of the drive IIRC, as it would 'relearn' the 0 %TPS voltage, and then show like 7% at idle after that when the voltage reading was working correctly again..

Now my car is high-idling again, sometimes, but I have not seen the TPS act up again. So, I'm looking for other explanations. No sticking of TB or cable either, or I would see it on the TPS%.

jclark311

I have the same problem, high idle sometimes 2 k, when rolling, come to a stop, and it goes to 900, LE2 Setup , PCM tuned by Bryan, no vacuum leaks, i will be watching this thread, and keep you guys posted on what i did to cure it.

jclark311

OK here is what i did to solve the problem, i reset the IAC, I got this off Shoeboxes website, Thanks Shoebox, and Bryan, Bryans tune is dead on!

Reset the IAC Position


· Depress accelerator slightly
· Start engine, then release accelerator pedal, run engine for 5 seconds
· Turn ignition "OFF" for ten seconds
· Restart engine and check for proper idle operation
It is NOT recommended to to push or pull on the pintle of an IAC that has been in service. The force required can damage the threads on the worm drive. Also, do not soak the IAC in any liquid cleaner or solvent, as damage may result. When installing a new IAC, you may move the pintle to match the measurement of the old one. The force required to move a NEW valve will not cause damage to it. Use engine oil to lubricate the o-ring. Tighten attaching screws to 27 lb. in.

Note that the 1993 IAC has a square electrical connector and the valve screws into the throttle body, instead of being held on by screws like those of later years.

1redTA

car idles at 1200-1500 while moving and will drop to 950 while stoped. also runs rich at wot..bucks at light throttle under 2000 rpm programmed by pcm4less it does get 22mpg interstate( I think it could get a little better) and abuses heads and cam ls1 cars I need to get it scanned and the tune tweaked.

CreatiVe2

same problem here, Idle fine at stop. and while moving RPM is at 2000. its been doing it on and off since i got a dyno tune from bryan, not saying he did it. i just built me 383 motor and had bryan rework the tune (via mail) and it does it all of the time now when im moving, i understand it could be a lot of variables. but this is on a whole new motor with all new parts. any ideas?

khojo16

i just started having this problem a couple days ago as well. all of the sudden, my car idles at 1500rpms sitting still, and hangs around 2000-2500rpms while moving in neutral. got an SES code P0507 the other day and reset it, and it hasnt come back on yet, but the rpms are still doing the same thing. any ideas??? i was thinking my IAC may be sticking bc it is a stock unit from 1996, and i have a new 383 with Bryan Herter tune...iac is one of the very few parts i have not replaced yet

shoebox

Something sudden sounds like a vacuum leak.

Injuneer

Did you check the throttle blades to make sure they are closing smoothly, and fully?

khojo16

yes the throttle blades are closing fully and smoothly, the stop screw has not been touched and is in the same position as when i originally set it, the TPS was replaced when I put the new engine in bc the old one had broken inside, and I set it to the voltage listed on shoebox's website, and I have a brand new MAF...i'm not too sure where to check for a vacuum leak, but last night when i took the car out, after an initial start-up, the idle was back around 900-1000 where it was tuned for, and then a minute later was hanging high again...

dangalla

i wouldnt say that mine started suddenly but it didnt show up until about 1000 miles after the build and tune. i have not driven the car in a long time but yeah it still has the problem

i know there is a parameter that is set for idle while moving that is higher than while parked, and the funny thing is that most of the time it works fine- while moving around 1200 and around 900 at a stop, and sometimes it just goes on its own around 2000. but the thing is that at a stop it is always perfect.

i think the only way to fix this for good is to have the tune changed so that the idle is the same all the time.

khojo16 - was your car tuned by bryan as well?

khojo16

yes i had a one on one dyno session with bryan and his tune was dead on and worked perfect for a year or so now. i have close to 6,000 miles on the build, and a couple days ago, i let my brother take my car for an alignment. i got the car back with a great alignment, and also an SES light with code p0507 and a hanging idle. i just noticed yesterday however that the o-ring on injector #8 is no longer making a seal between the injector and the intake manifold. instead, it is raised on the injector and cracked/dry-rotted. could that be creating a vacuum leak and causing this problem? or is that just another problem i need to fix?

LearJet

That will definatly cause an induction leak. get a new o-ring.

khojo16

i have tons of new o-rings, its not a big deal at all to replace it...what will an induction leak do though??

Injuneer

"Induction" leak is another term for vacuum leak. The air is leaking into the manifold, and its air that causes high idle, and forces the PCM to have to correct the A/F ratio, using the long term fuel corrections.

dangalla

while idling spray it down with some 2+2 or carb cleaner and listen for a change in tone or idle quality