Malibu Surging Problem Advice Needed

I have a 2000 Malibu, automatic transmission. While slightly accelerating at highway speeds (as in up a gentle hill), after the transmission shifts out of overdrive and into 3rd gear it begins surging. The engine rpm is around 2500 and it will fluctuate 2-300 rpm. I took it to a garage, they said it was a transmission problem. I took it to a transmission shop and they thought it was a fuel / injection problem. I don't have any codes coming up. I just replaced the EGR valve which made the problem better, but is still there. It doesn't happen all the time, but seems to get worse in warmer weather. A parts man suggested a throttling valve? Not wanting to just throw parts (and money) at it until I find something. Any other thoughts?

Welcome to AF. Low fuel pressure for one can cause this, restricted fuel filter. A full scan will tell if the trans is functioning properly and in the hands of a good tech, fuel trims and sensor inputs may point to the problem.

I'm glad you asked this question. I have the same problem. Only codes that was stored when they we're read was for the EGR valve. Engine light hasn't came on since I replaced the plugs and wires. I swear at times it acts like it has a hotrod style cam in it if you let it sit and idle. Mine doesn't do this all the time either, just sometimes. I really don't think it's a transmission problem. I'm going to check my fuel pressure, and probably change out the EGR valve, but I can see now from your post that this probably wont help, changing the EGR valve that is.

This problem is all over the net, with no real clear fixes. If you find you're problem, please let us know what it is. I'm leaning toward the catalytic convert being about half stopped up, but then again I was also thinking it was the EGR valve. I've read posts where folks have changed torque convert, torque covert lockup soleniod, and all sorts of parts and still has the surging. I'll find it eventually. ...I guess... <shrungs>.

I did notice the AC kicking on and off, on the heater controls. The little LED lights would flash on switch from inside out to fresh air. Thought that might have something to do with it. You know the AC compressor kicking on and off would sure put a stain on the engine, I would think anyway. That's an easy fix though, you have to take the heater controls apart and clean those little contacts in there. I done mine today, we'll see if that's what it was I and I'll post back with results. I have a PDF document with clear instructions on how and what to clean if anyone needs it. Also will post back if it's low fuel pressure.

Thanks for the suggestions, but I don't think it is restricted fuel line. When it is surging and I step on the gas, it kicks down into a lower gear and then runs fine at a higher rpm. One thing the transmission people wanted to do was an intensive injector flush. I have put several cans of injector cleaner through it (many different brands) but that didn't seem to do it either. I may have been money ahead having them do it.

I can report that it's NOT the heater controls kicking the AC on and off thats causing it.

It seems like we have come to a solution. I took it to a garage. He first suggested a tune up so I put in new plugs and wires. It seems to have taken care of it. The garage put it through pretty extensive tests and couldn't find anything else. No codes in the transmission or engine showing up. The man checked an internet site they have available and said there was one situation listed where the transmission indicator lever showed it was not in the same gear as what the transmission actually was (this was not my case). He also mentioned that there was a software patch available for the car, but didn't think that would be relevant either. I hope this helps others, and thanks for your help - it's appreciated.

I had same problem. I removed the first sencor past the air filter and cleaned off the buildup of carbon from the sencor using soap and water. That fixed the problem for me. Hope it helps.

Please check the dates before replying this thread is inactive, thanks.