Transmission Issue

2004 Impala 3.4 130,000km/80,000miles

Issue started yesterday, when driving @ low speed around 20k up to about 40 k there is a kick when accelerating, almost as if I put it i neutral pressed the gas then dropped it into gear. However there is no revving, tranny fluid is fine and no dash lights on, it only seems to happen midday, drove home after work and took it for a nice ride last night, this morning on the way to work no problems, but at noon it acted up again. No other issues lately (which is strange :icon16:) any help would be greatly appreciated.

I would check you're catalytic converter. My impala acted like it had tranmissions problems but it turned out it was a plugged up catalytic converter causing the car to not shift right and run crappy.

I was just thinking the same thing I have noticed some change in acceleration, any symptoms that I should look out for? Just talked to a fella I know and he is dropping off his scanner in the morning hopefully going to get it looked at this weekend.

Just got off the phone with the local dealership based on my description of the issue he feels its the cat, he also said the warranty has been extended to 130,000 km or to the year 2012, sadly im 5000 over but he said if it was indeed the cat I could complain and the manager would warranty it.
Going to get the fuel filter changed first thing tommorow as well.

Just got off the phone with the local dealership based on my description of the issue he feels its the cat, he also said the warranty has been extended to 130,000 km or to the year 2012, sadly im 5000 over but he said if it was indeed the cat I could complain and the manager would warranty it.
Going to get the fuel filter changed first thing tommorow as well.


When my car was messing up I thought giving it a complete tune up would fix it. I thought maybe it was mis-firing. I changed plugs, wires, air filter, oil, transmission oil, tranmission oil filter, fuel filter and also added the lucus transmission fuild additive. Needless to say the car was still running poorly. It was acting like it was only running on a few cyclinders. I then took it down to a local shop and they informed me it was a bad cat. This car is known for the cats get plugged on them. There was no exhuast coming out of the tail pipe. I would have somebody rev on the car while you feel for exhuast pressure at the tail pipe. Or another way to test, you could go by the auto store and purchase a pressure gauge. Then t it into the vacumn line next to the fuel rail and test it that way.

Also I had a muffler shop replace the cat for around 400 - 500. I cant remember excatly how much. The car a year later would not pass inspection. It was failing 3 things on the inspection. O2 sensor heat, Cat no ready or failed and evap system not ready or it failed. So beware if you do take it to a small muffle shop and not the dealership.

So I hooked up a reader and it isnt throwing any codes, according to that everything is going fine, going to change the fuel filter(needed to be done anyway) and have the car looked at monday morning hopefully something can be found.

I have the 3.8 LS and it is doing the same thing when I'm acclerating. Will try some of your suggestions and repost if I find out anything new. I've kept up on its maintenance schedule and cannot figure out why this is happening at only 60,000 mi. It's an 04'

Easy way to check is to remove the forward O2 sensor and see if the symptoms go away. I wouldn't drive it very far with the sensor out, but a little bit should be fine.
A shop can do a back pressure test to confirm a plugged cat, it should be pretty cheap and quick.
GM made a bunch of bad cats back around 00-03, I think. That's why there is an extended warranty on them.

Phoned a shop on the weekend, wanted some simple repairs done the mechanic that was "supposedly" the manager/head mechanic didnt know what a back pressure test was so needless to say they didnt get my business. Just dropped it off at a shop across the street from work and they seemed quite competent. Will keep ya posted.

I have the same problem on my car wehn driving in really heavy traffic. I don't think it is the cat, probably just the transmission getting old. It doesn't slip at all when in gear just shifts a little hard.

Mechanic called back, fuel filter was terrible (which I knew) and the MAF was dirty and now they are going ahead with the back pressure test, heres hoping it fixes the issue. Next up new pads/rotors and plugs/wires.

EDIT/
Just got the car back, CAT seems fine back pressure is in a reasonable range, im thinking this should cure it, going to take some long drives over the next day or two to test it out.

That is good news, hope it works out for you. Did they replace the MAFS? If needed to, you can clean it you're self. They sell a spray at the local auto shop.

Good news indeed. The did just clean the MAFS that was on my things to do list as well but they beat me to it. Took it out last night for a long drive, ran good no issues, unfortunatly I'm sick as a dog today and didnt make it to work to see how its running.