2001 Alero Trans Surging

I have a 2001 Alero with a 3.4L and a 4t45e trans with 125,000 miles. It seems to go into the gears fine, but slipping in and out of 3rd and 4th gear. When this happens the RPM's shoot up about 500 - 1000 and back down. There are no DTC's and no lights on dash. I thought the best thing might be to check for PCM update. Any help would be appreciated.

Craig

Welcome to AF.

When was the last transaxle service? New ATF and screen filter? Although it is hard to do did you check ATF level?

I don't know when the last service was performed. I bought the car on Saturday, and it started acting up right away. I did check fluid. (What a pain). I have not replaced trans screen filter. It feels like if you were driving in a standard transmission auto and popped the clutch in and out while maintaining position of throttle.

OK I just scanned the car and got a stored P0128 and a pending P0440. It seems that I read about an intake air temperature (IAT) sensor causing some problems with transmission function. I don't know if this is of any help but thought I would add.

That is correct. Common problem if the IAT is bad or disconnected or if you install a CAI and do not install it properly. Just check out our old/archived threads on the issue. Also, GM issued a technical service bulletin (TSB) on the issue.

The P0440 DTC is an evaporative emissions issue but not necessarily a bad or loose gas cap. Check the purge solenoid electrical connector at the engine area and the vent solenoid at the charcoal cannister at the gas tank area.

Well, I guess I can rule out the IAT sensor. It reads 5v and shows 78.8 f on the laptop. Is there anything else you know of that could cause this? I cleared the codes and will take it back on the road tomorrow to get a better Idea of how it's acting. also I am going to get the PCM flashed and re-loaded saturday at the dealer.

By the way the P0128 DTC is a possible issue with engine warmup time and the thermostat.

Can any of that cause the trans surge? the connector to the trans is clean and dry. I cleared the codes and nothing appeared yet. What will happen if I disconnect the plug to the trans and drive it? Just looking to see if popping in and out of engagement is mechanical or electronic.

Disconnecting the tranny electrical connector won't do any good. You'll lose all automatic shifting, torque converter functions, and it will go to so called limp home mode.

You might consider starting with the basics like a basic tranny service. ATF and screen filter and go from there. It should have been done back at 100K miles anyways. With your mileage do not do any type of flush. Just a pan drop service.

I didn't try disconnecting trans plug. I did drive the car home from work (60 miles). I noticed that the car was surging until I accelerated. Once I pressed the gas the surging stopped and the RPM’s dropped to normal, and everything was smooth. The only problem I had was cars kept getting in my was and kept me from accelerating any further (90mph).

I did the transmission maintenance (Filter & Fluid), but it didn’t help. I also took the car in to the dealer and had it scanned. No codes, but there was an updated program. They loaded the program, but no improvements. The service tech rode with me, and his scanner, but could not figure out why the car is doing a “Neutral Flare”. Maybe I should take it to a transmission specialist, but the last car I took in he wanted to rebuild the transmission, ($1,800) and all I did was to replace the solenoids ($65.00 EPC TCC).

Well, I'm getting ready to do the Trans Swap, but I came across some interesting info about the evap canister purge solenoid. It says splice S107 should be inspected for corrosion. I did have this code, reset it and have had no codes since.

I did the R & R about a month or so ago. It wasn't so bad. I replaced a leaky rack while I was in deep. I took a solid 12 hours and some bloody knuckles, but I love the car now and it was well worth the work. I have heard other friends complain about problems with this trans. I know the 2001 only fits in the 2001. Thanks for all the advice BNaylor.