MAF/ Trans Problems

[fast_ga]

Well after months of diagnosing electronics and mechanical parts of my trans and finding nothing wrong to cause soft and erratic shifts, i got brainy tonight and swaped my stock MAF back into the car and poof, trans problem gone! Anyone else eperienced trans problems after installing a aftermarked MAF or porting and polishing your own?

[Craig99SE2]

I run the GMS MAF with no problems. Porting may cause problems because you are throwing off the calibration by porting and/or removing the screen. I'm still not exactly sure how the MAF would affect the trans shifting, but I am trying to dig up some info on that. All I have found so far was what I posted in this thread:

http://www.grandamgt.com/forum/showthread.php?s=&threadid=19450

[Craig99SE2]

OK, what exactly is the problem you are experiencing?

Just looking quickly at some GM PowerTrain info, the PCM uses the MAF input to determine the load on the vehicle (i.e. trans). Under hard acceleration, airflow increases significantly with respect to time and the PCM applies more line pressure to the transmission. It also controls TCC lock-up when a steady state (of airflow vs. time) is detected.

With this info, it would make sense that the shifts are softer. By porting the MAF, you are now allowing more air to enter for a given output since the unit was not re-calibrated post-porting. The engine will apply more power to the transmission than with the stock MAF at the given throttle position. The problem is that the signal controlling line pressure is also less than the signal of equivalent "airflow" NOT throttle pressure.

For example:

Stock MAF:

Airflow = 10 lb/min.
Output = 32KHz

Ported MAF:

Airflow = 12 lb/min.
Output = 32KHz
Airflow 10 lb/min.
Output = 28KHz

Because you have an incorrect calbration on the MAF by porting, the PCM thinks you are going slower than you actually are and is not increasing the trans line pressure accordingly.

In theory, a GMS or *ANY* calibrated aftermarket MAF shoudl not have this problem. I know a few people did, but I think they cleared it up by getting it re-called. If the cal was done by Pro-M, it should work just fine. Mine is the GMS with Pro-M cal and I do not have any problems at all. As a matter of fact, mine shifts harder under acceleration after installing the GMS MAF than it does with the stock MAF.

It looks like the bottom line is that modifying the stock MAF is a BIG NO-NO!!!

[3400MAN]

I'm working on the same thing right now. Trying to find specifically how the MAF influences the Transmission.

Follow this link to some interesting info:

www.autoshop101.com/forms/h34.pdf

This explains the different types of MAF's used and makes the same statements regarding load that Craig mentioned above..

Just an FYI.....

[3400MAN]

Mass Air Flow (MAF) Sensor
The Mass Air Flow (MAF) sensor measures the mass of air flowing into the engine. The MAF sensor output signal is used by the powertrain control module to calculate injector pulse width. For transmission strategies the MAF sensor is used to regulate Electronic Pressure Control (EPC) , shift and torque converter clutch scheduling.

Quote from another website regarding MAF function on automatic transmissions.....i.e. MAF also determines when the car shifts.....