Engine revving while driving

[stripgirl]

Does anyone know what to look for when driving at a constant speed the transmission starts revving on its own? It's slight but you can feel it. And you can watch the RPM's going up and down. Then it just stops (not the car but the revving).

I was going to check the transmission fluid but apparently GM didn't make that very easy for the consumer. As far as I can tell, you must have to check it from underneath the vehicle, or else go to the dealer. However it is not leaking any trans fluid.

Anyone else have these problems?

Thanks in advance

2002 Grand Am GT 3.4L 86,000 miles

 

[capnvonbaron]

I have the exact same problem, exact same car. It seems to happen when the car is still cold. Usually around 100-200 rpm, in the 40 - 50 mph (1300 - 1800 rpm) range, quits after the car has had plenty of warm up. I have 92k on the car, had a full fuel system cleaning not long ago. Had the gasket problem fixed not long ago too, although I noticed it the first time the temperature got down into the 40s before I fixed the gaskets. However, the dumb abs/ets sensor just went out, so I have to fix that now and I wonder if that might've had something to do with it. Will keep posted. Anyone else out there with this problem?

-capn

 

[stripgirl]

Yes, please let me know. I actually just bought this car in September when I got rid of my lease. I haven't had any problems until now. But I haven't noticed that it only does it when it's cold or anything. Seems like it does it warm or cold, but definitely in the 40 - 50 mph range. However, it could probably use a fuel system cleaning.

If I find out what my problem is I'll make sure to let you know. A friend of mine is an ASE certified master mechanic and told me to watch for a couple things so he would have a better idea of what it was. His guess originally was the intake manifold gasket, but after driving it and seeing the problem he thinks it might be the torque convertor unlocking and coming out of 1:1. I will be doing some documentation over the next week for him but he thinks MAYBE a trans flush should be first. But it sucks throwing out $100 not knowing.

I'll post as soon as I talk to him again.

 

[capnvonbaron]

I was starting to wonder if it might be the tranny too, to tell the truth. Just based on the somewhat limited nature of the revvs bouncing. I think I've noticed it also when getting up to highway speed; when you give it a good amount of throttle before its gotten to its 5th speed, up in the 3000rpm range it seems like it doesn't want to deliver steady power. I think it has to do with how much load is on the motor/tranny? I may just have them flush the trans when I get the wheel hub replaced. 92K is probably long enough to go without one, or...?

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[99Green GTP]

i used to drive a 1996 grand am, with the 4 speed automatic and a v6. now this is likely either the same or a very similar transmission as what was in my car. I actually had the transmission replaced, but here is what was the problem i my car:
Attached to your lock-up torque converter solenoid is a valve. It is made from aluminum and to be honest, i can't remember whereabouts it is located, because it was a while ago and i only looked at it a few times. Anywho, this valve has something of a little piston inside of it, also made of aluminum, and over time both the casing and this little piston sort of thing will wear out and start to get stuck. Once this happens, your torque converter will engage/disnengage rapidly. Yhe torque converter is what helps the transmission to go into overdrive when you have stopped acclerating and are trying to hold a constant speed. In my car, this revving problem was most prominnt when i was going up a hill, or around a corner, because the car was nto sure if it should gear down or not. Eventually, this problem will worsen, and the car will not go into overdrive, and your engine check light will come on. The lack of overdrive will occur when the car is hot, and the valva has expanded and become stuck, and the revving happens when cold, and the valve is sticking/unsticking repeatedly. Furthermore, the car will burn about 1/3 more gas if it cannot overdrive because at 50 mph you will be at about 2300-2500 RPM instead of 1700-1800. In the advanced stages of this problem, the car will begin to stall out when you stop etc., and the revving when cold, sticking when hot will get much worse. Take it to a chop and sugest this may be the problem, and they can check it out. I never had mine repaired, but a gentleman i know had this repaired on his GMC Jimmy when it displayed all of symptoms and it cost him $500. I believe on some vehicles the valve is on top of the transmission, and the trans must be removed to access it. If not it is an easy fix. What should be done, is that the valve is drilled out, and a new one, made of much higher grade aluminum is put in it's place. Post back with anymore questions, I can probably help, I spent a lot of time trying to figure this out on my car and I learned a lot in the process.

 

[capnvonbaron]

oops, totally forgot to update. I got the car looked at a week ago. The wheel hub assbly was indeed bad, but that probably wasn't the problem anyway. About $300 parts/labor later, everything fine there. Put a tranny flush on top of all that for another $100, and the revving in top speed has gone to nearly nonexistent. Right after the work was done, it still seemed to be there just a tiny little bit. It may have been my imagination, and I haven't even looked in the last few days so it may have gone away entirely after the new fluid worked its way in.

 

[stripgirl]

Sorry about so late getting back to this. My car was at the dealership for two weeks for a warranty issue. However, I was finally able to get a transmission flush yesterday. And I am happy to report that I have not had any revving problems since. It may be too early to tell but so far I am exstatic that my problem only cost me $95.00! I'll let you know if I have any more problems.