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Hello! I have a Pontiac Grand Prix that I have a peculiar and intermittent problem with. Sometimes when I’m in a low gear (usually just after starting the car or inching up to a traffic light) I will apply the brakes and instead of stopping, the car will actually lurch forward a couple of feet. It’s almost like I can feel that the brakes just aren’t catching correctly, but I’ve had them checked (and the brake lines drained etc) and they can’t find any problems. My ABS/Trac-Off lights will come on, there will be an brief clattering noise, but the car doesn’t actually stall, the traffic light turns green and I drive on without having to re-start the engine or anything.
When I asked my mechanic about cleaning the IAC or the throttle body, he wouldn’t even consider those as the possible problems, and said that my internet research about that stuff was pointless. I can’t duplicate the problem for him and so he says he doesn’t know enough about the car to really diagnose the problem unless it completely breaks down.
HELP PLEASE!
I’d say you have a transmission problem for sure. You’re probably at the beginning phases of failure and it will just end up getting worse over time and you’ll lose more and more gears, and pretty soon it won’t shift at all. Try and check the fluid level, and also see if the fluid is very dark and/or smells burned. If so, you’re definitely going to need some transmission work done. You may be better off, price-wise, to look into getting a used transmission instead of rebuilding the current one. It is usually less expensive and should come with a warranty. There are lots of the Grand Prix/Monte Carlo/Lumina/Regal vehicles in the junkyard, so transmissions are readily available.
What you’ve got happening is quite common. The reason the ABS/Trac Off lights are coming on is because you are experiencing an ABS event, even when you aren’t supposed to. This is due to one or more wheel speed sensors being faulty. This can be the actual hub bearing itself, which has the wheel speed sensor as an integral part, or the wiring to the sensor which can become corroded from moisture intrusion. The noise you are hearing when you lightly apply the brakes is the ABS unit activating because it’s lost a signal from one of the wheels. This will cause a feeling of little or no brakes and the vehicle not stopping as it should. I would recommend taking the car to a GM dealer where they can scan the ABS module for any problems. You’ll be most likely looking at replacing one or more wheel hub bearings and/or the harness to them.
I’m somewhat hesitant to take it to a dealership though; the last time I went to my local GM for my Pontiac issues, I felt like I was dealing with a bunch of guys trying to sell me a time-share. It was a high-pressure sales guy trying to convince me of a bunch of stuff I didn’t need, so I’ve just never gone back there. I’ll do my best though.
Go where you feel most comfortable, but insist on factory GM parts for sure, or you’ll be replacing them again and again.
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