94 LT1 Idle Surge at Temp when in gear HELP!
 

Hi Guys. Brand new member here. I have a 1994 Coupe with 58k on it. The car is in fantastic shape and runs great EXCEPT once it reaches around town operating temp. Once I pull up to a stop light while in gear (automatic) it begins to rev up to 1,300 or 1,500 and is "hunting" for an idle speed. When I pop it in neutral or park it drops back to 500 R's (there are no codes). I have replaced the throttle Position sensor, Taken the MAF out and cleaned it and replaced some vacuum hoses that had signs of bulging. The MAF looked good but I sprayed it down with Carb Cleaner anyway. I had the car out yesterday and I gave it a few opportunities to do it but it didn't. However, this is an intermitent problem. Can anyone tell me what their thoughts are on this problem? Replace MAP, MAF...any other suggestions? Thanks a bunch!
Ken

RE: 94 LT1 Idle Surge at Temp when in gear HELP!
 

How long does it hold steady rev's, when you do neutral at this point?

When slowing to an intersection and you let off of the gas, before you apply brake, does the tach go ALL THE WAY down, to idle speed?

RE: 94 LT1 Idle Surge at Temp when in gear HELP!
 

When the vehicle is out of gear or in park the revs are normal... holding at about 500 rpm. As soon as you go back into drive it begins to hunt again shooting up to 1500 rpm and back to 500 within a couple of seconds. When driving and coming to a sop sign, now that you mention it the car does seem to drop to idle rpm. I do not think the thing has ever downshifted on it's own.
Thanks, Ken

RE: 94 LT1 Idle Surge at Temp when in gear HELP!
 

It's your torque converter. It's getting a signal at the solenoid to lock up, at the improper time. And it isn't UN-locking either, as you come to a stop. (Now is a very good time to get familiar withthe tranny - filter and fluid change). 99 % certain it's electrical (TCC solenoid). Cheap fix, but difficult to find the problem, andcould cost a few $$$ to find. BUT, could even be in your brake pedal switch. I'm lookin' for where the diagnostic info was.

Some of the other guys in here might back me on this (or lead elsewhere, too)...

Say your prayers and do penance in the meantime.

RE: 94 LT1 Idle Surge at Temp when in gear HELP!
 

Well, there is something I have not looked into. Would this cause an intermitent problem?

RE: 94 LT1 Idle Surge at Temp when in gear HELP!
 

CWB,
I just took the car out and I was mistaken. It doesn't drop right to idle RPM when you lift off off the throttle. I seems to wind down a bit slower.

RE: 94 LT1 Idle Surge at Temp when in gear HELP!
 

Yup, it winds down slower, I'm almost 100%, because the torque converter hasn't disengaged. Yes, it could well be intermittent, being an electrical problem.

Here's your diagnostics flow chart. DON'T be intimidated. Print it out, study it, and re-write it into your own flow chart process. If the dealer does this diagnostic process, YOU WILL PAY, and you can do it your self...

http://autorepair.about.com/cs/troub.../aa061701a.htm page links at bottom.

Make sure your moto keepslow rev's in neutral and park. If it didn't, we'd be going into a vacuum leak in the intake, which doesn't care what gear you're in. Pulling/rev'ving when only in gear, and not downrev'ving at speed with gas pedal off, is torque convertor/TCC clutch solenoid.

RE: 94 LT1 Idle Surge at Temp when in gear HELP!
 

Spraying the MAF with carb spray is not a good thing since there is a circuit board in there. I doubt the torque converter is giving you problems since the car is not dieing. If the converter was staying locked up, the car would die at stops just like a manual with the clutch engaged. Have you cleaned throttle plates? Try cleaning plates, then disconnect battery for a couple of minutes, then reconnect so the ECM can relearn idle position. Also, would need to see what TPS voltage is @ idle and is it stable? Also, can spray around intake with carb spray to check for manifold vacuum leaks @ idle.

RE: 94 LT1 Idle Surge at Temp when in gear HELP!
 

Thanks. I will definitely look into that. That is somewhere I have not looked.
I appreciate all of the help! Looking forward to getting this red beast back out on a regular basis!
Ken

RE: 94 LT1 Idle Surge at Temp when in gear HELP!
 

Yup, the TC locked-up would cause the motor to stall when stopped. Increased impellor pressure would not.

If he was getting carbon build-up behind the butterfly (indeed, a common problem), his idle wouldn't drop when he puts it into neutral, or park. Right? And vacuum leaks are the same way - they don't care what gear you're in. He said neutral and park are steady, low idle.

Vikes, does your gas pedal seem to hang, or stick,as you begin to accelerate?