I have a 2004 Monte Carlo SS (non-supercharged) that has an intermittant trans issue. When driving at 35 and then applying throttle SOMETIMES the trans balks or lurches or acts like is skips or cannot find a gear. Car has 55K on it and has not been beat. Also just one time the engine dropped out for a fraction of a second. There are no CODES and no SES light.

It has been suggeted to me that there could be a vacuum leak. Also a while back the dealer replaced the Mass Air flow valve. This defect caused a signficant jerking of the car before it was corrected.

I still have a GM extended warranty and just had the car in the Chevy Dealer for a week and they cannot locate the issue, even though I demonstrated it to their mechanic.

First what do you think about the vac leak theory? And where is the Mass Air Flow Valve?

This has been a decent car for us and at 55K I rather hang on to it for a couple more years.

Sparx22

[This message has been edited by sparx22 (edited 07-22-2009).]

My in-laws' 2000 Impala, same 3.8, around 45k miles on it, has similar symptoms. Feels like the torque converter is locking and unlocking around the 45 mph point. Dealer tells them it's common, and can't really fix it. I told them to take it to a different dealer.

My 2000 impala with 3.4 does it too. But has 135k on it.

quote Originally posted by 2birds: My in-laws' 2000 Impala, same 3.8, around 45k miles on it, has similar symptoms. Feels like the torque converter is locking and unlocking around the 45 mph point. Dealer tells them it's common, and can't really fix it. I told them to take it to a different dealer.

This is what is sounds like to me also. Does it do it worse when say going up a hill at around the same speed?

Well as you know all Dealerships are not created equal. O’rielly Chevrolet in Tucson had my Monte Carlo for 7 days and was not even clever enough to duplicate the problem, even after I demonstrated it to their engine Tech, a sincere individual btw that admitted he was not a transmission mechanic and could not fix the problem.

So they were going to drive the car but this guy, that guy, and the man in the Moon could not duplicate the problem. So I went back this past Tuesday to show them the problem and they allowed me 10 minutes to duplicate it and it would not buck. The next morning (Weds) I picked up the car and of course got the trans to act up no less than 8 times on the way home. Later took it to Watson Chevy also located in Tucson.

Watson was nice; a white shirt tech connected a code reader and had me drive the car. In no less than 2 minutes the problem showed up. Trans was missing shifts and bucking. Tim the tech had me pull off the road and put the car in PARK. He said the readings he was getting on his scanner were strange for the "learned" values of the transmission. So he reset the trans memory. I had considered disconnecting the battery on the car to reset these very same values but they MUST BE RESET WITH A SCANNER. TY GM one more PITA.

Anyway right from that point the car shifts as it did when we purchased it in 2004. Nice smooth shifts, no loss of gear engagement, no revving engine. It took a whole 20 minutes to solve the problem!

I have a GMAC extended warranty and O'Rielly (rip off) Chevy wanted to charge me $105.00 for my visit, but I got them down to $52.50, as far as I am concerned I am due a refund. They can take any (empty) apology and shove it up their a$$.

The major issue I have with this is the need for GM to do BETTER; they are currently hanging by a shoestring. Some of GM's downfall is due to crap customer service. So if you have 3.8 that has a trans acting goofy, this might be the answer. Oh, and stay away from O'rielly Chevrolet in Tucson Arizona.
Sparx22

quote Originally posted by sparx22: Tim the tech had me pull off the road and put the car in PARK. He said the readings he was getting on his scanner were strange for the "learned" values of the transmission. So he reset the trans memory. I had considered disconnecting the battery on the car to reset these very same values but they MUST BE RESET WITH A SCANNER. TY GM one more PITA. Anyway right from that point the car shifts as it did when we purchased it in 2004. Nice smooth shifts, no loss of gear engagement, no revving engine. It took a whole 20 minutes to solve the problem! Sparx22

OK, first off, the GM's have had to have a scanner to reset the codes since at least '99. My Silverado is that way as well. That's not a big deal, IMHO, because you shouldn't be working on these without a scanner anyway.

That said, what he reset was NOT the codes, it was the "learned values". This is similar to clearing the prom and reloading the default original values. You've NEVER been able to do that without a scanner/programmer with OBDII as far as I know.

You said that you had Mass Airflow issues in the past that cause the engine to Miss or something to that effect. Most likely, when the engine was causing issues, the transmission was trying to compensate and it should have been reset when the engine problems were fixed. They weren't. THAT was a dealer/tech oversight.

I'm sure it was an aggravating problem for you, but what the heck? I mean, you said yourself you couldn't get the car to duplicate the issue at the first dealer. Intermitten problems are a real PITA to figure out for anyone and if you think Ford, Chrysler, Toyota, Nissan, or anyone else never has these issues think again. You're not going to get perfection from any machine no matter if it's from GM or anyone else, to expect it is going to be a disappointment.

John Stricker

I know he reset the learned values. I was able to demonstrate the problem on the first test drive, did not have enough time on the 2nd test drive, due to an impatient service manager. The mass air flow problem was last year, didn't have trans issues after it was replaced. I was not looking for perfection only a trans that acted as it did 6 months ago. I did not spend extra money for the warranty to have them fail to correct a problem.

I could go into how Chevy is blowing myself and hundreds of other guys off regarding a factory defect in the paint on the rear deck of our C5 Corvettes, but I won't! That car was $43,000, YES I do expect GM to fix it for free, especially since there is a TB on it! Let's face it the less GM spends the better... bad PR in my book.

Anyway I have a car that is running as it should and one dealer I can trust, maybe!

[This message has been edited by sparx22 (edited 07-25-2009).]