I pulled Bonne out for winter duty a couple weeks ago. It will intermittently idle at 1500-2500 rpms. By unplugging the battery, MAF, IAC, or TPMS, I can usually get it to idle normally, but everytime it seems to take a different sequence of sensor unplugs to fix the problem. Last night i drove for two miles at 55mph with my foot off of the accelerator. I cleaned the MAF in April, and the IAC and TPS were both replaced in fall/winter 2014 because the TPS legitimately failed, and while cleaning the throttlebody, the IAC fell apart. Which tree should I start barking up first?

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1993 SSE Since 11-12-2000
2011 Camaro 2SS
2006 Silverado 3500 4x4

Can you scan live data? That would be what I would do first because that takes the guesswork out of it.

I would also check throttle linkage and cruise control linkage too, just to ensure the throttle is closing fully.

Edit: My opening round vote is TPS, because I think anything else in that list will set a code if readings are not consistent with other readings. IAC is second, but I believe it's position is monitored so I would expect that to set a code if it is not shutting properly.

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~Randall~


1993 Buick Park Avenue - 197k - Some odds and ends done - Simply won't die
1994 Buick Regal - 78k - Bone stock - Always ready for a good kicking
1990 Oldsmobile 88 - Gone to a better place

No, unfortunately only have a Cummins scanner for our semis. The throttle/cruise cables aren't the culprit, but i haven't completely ruled out a vacuum leak.

What kind scanner would you recommend than can scan OBD1 and OBD2?

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1993 SSE Since 11-12-2000
2011 Camaro 2SS
2006 Silverado 3500 4x4

Try disconnecting the throttle and cruise cables. One could be hanging up and just keeping the TB open a slight bit, and the pcm doesn't handle it quite right sometimes. Mine has been known to do that.

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WHITE WHINE - 1992 SSE Supercharged 236.26 ci (.040 Over) 15.090 at 90.2 MPH on old engine w/ slipping trans & melted O2 sensor - Gen 3 M62 and matching TB, Gen 2 Pully, Zillamotorsports Ported LIM, YT 1.72 Roller Rockers, SII FPR & Injectors, Hypertech Thermomaster chip w/ 160 Thermo, TransGo Shift Kit, Infinity/Pioneer Speakers & a 10" Alpine Type R Sub, all the watts, 140 amp Alternator, Ricepipe CAI w/ heatshield, Pilot Angel Eye Foglights, Clear Corners, '02 17" Chrome Bent 5's, Magnaflow F-Body Muffler and Hi-flo Cat, Ceramic Coated Ported Exhaust Manifolds, Fan Override, Monroe Reflex struts, red calipers
2009 G8 GT - Sport Red Metallic, loaded, SOLO Axlebacks, Rotofab Intake, Tuned, autodim mirror, removed intake manifold cover, HSV GTS triple gauge pod, two tone red-hot shifter and HSV SuperSport steering wheel, GXP rear sway bar and diffuser, 3.45 diff and various Camaro suspension bits, LED Taillights

Was able to finally open the hood during a high idle today. The throttle is closing with slack in the cables, but it looks like the return spring on the new TPS is weak. Pulling the sensor arm back by hand brought the motor down to idle. Thanks!

edit: ended up just tweaking the sensor arm to bring the idle voltage down to 0.31v

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1993 SSE Since 11-12-2000
2011 Camaro 2SS
2006 Silverado 3500 4x4

Thanks for posting the solution to the problem.

What brand was the replacement TPS, if you can recall?

Carquest. It tested 0.48v with the throttle closed before I took the pliers to it.

Edit 12/27/15: Tweaking the arm helped for awhile, but i had to replace the sensor a few weeks ago. All good now.

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1993 SSE Since 11-12-2000
2011 Camaro 2SS
2006 Silverado 3500 4x4