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2003 Pontiac Montana Acceleration

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New User

Nov 2, 2014, 9:21 AM

Post #1 of 3 (1216 views)
2003 Pontiac Montana Acceleration Sign In

I have a 2003 Pontiac Montana mini van with a 3.4 Liter engine and 103,000 miles. The problem I am having is the vehicle will accelerate on its own. It is not a sudden thing, rather a gradual acceleration. For example, I can pull to a stop sign, take my foot off the brake, and the vehicle will start off at a normal idle speed. It will then continue accelerating on its own as far as I will let it. I usually stop it at 45 mph. Once I apply the brakes I can bring the car back down and stop it with not much trouble, but I do have to push hard on the brake to fight the engine. This usually only occurs when the car is warmed up after driving for 15-20 minutes (sometimes less). I have had it to two different repair shops (one a GM dealer) a total of 4 times. So far they have: Replaced the Throttle Position Sensor, reprogrammed the ECM, Cleaned the throttle body, removed and replaced the Idle air control valve, checked all wiring for chaffing or bad connections, checked the mass air flow sensor TPS switch and IAC motor, and replaced the MAP sensor. Nothing has fixed the problem. Mechanics are stumped. Any help would be appreciated.

Hammer Time
Ultimate Carjunky / Moderator
Hammer Time profile image

Nov 2, 2014, 9:47 AM

Post #2 of 3 (1208 views)
Re: 2003 Pontiac Montana Acceleration Sign In

There is no excuse for them not finding this if they can reproduce the problem. They can drive with a scanner and see what all those components are doing at that time. This is not an electronic throttle so the issue has to be obvious to a trained technician. My guess is there is a very large air leak into the intake somewhere. A smoke test would easily find that.


We offer help in answering questions, clarifying things or giving advice but we are not a substitute for an on-site inspection by a professional.

Ultimate Carjunky / Moderator
Discretesignals profile image

Nov 2, 2014, 10:07 AM

Post #3 of 3 (1203 views)
Re: 2003 Pontiac Montana Acceleration Sign In

I agree. Monitoring data stream information, sitting down, and evaluating the data is much cheaper than playing swaptronics. Sounds to me like someone isn't actually troubleshooting properly.

Since we volunteer our time and knowledge, we ask for you to please follow up when a problem is resolved.

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