2007 MS3 bucking/jerking? (p2138 + u2023)

Hey all! It's been a while, I remember the old mazdaspeed forums from before. Glad to see things are still going!

I was hoping to get some help with this issue I've been having. It started about 2-3 weeks ago. Pretty much, when in lower RPM's in 1st and 2nd gear (usually below 2500), the car will randomly start to jerk and buck, and the only way to get past that is to floor the gas pedal and quickly switch to the next gear. This doesn't happen in 3rd gear or above for whatever reason. The first few times it did this, no codes were thrown. The most recent time actually caused the engine to throw a P2138 and u2023 code, and also limited the speed I could go to no more than 20 mph. I quickly pulled over to the side of the read when this happened, turned off the car and restarted it, and the car drove normally after that.

Doing some research, it seems that this may have to do something with the throttle body, throttle body wiring or pedal positioning sensor if I recall correctly. I already cleaned the MAF, checked the hoses/lines, recently replaced the spark plugs (about 10k miles ago) and removed/cleaned the actual throttle body. I thought that initially fixed it until last night when I was driving around again, the same thing happened (but the car didn't limit the speed this time, and still, no codes were thrown).

Does this sound more like a sensor thing going on? Or wiring that needs to be checked? Only modifications done are a Cobb intake and a AP tune (the generic, out of the box stage 1 I believe). I really don't know where to go from here as I've read it may not actually be the sensors but some wiring or ECU issue? Could it be my battery (it's old, has had to be recharged a few times + added distilled water into it to help keep the charge).

 

Easiest fix would be to replace the battery, especially if you know it is old.

If you look at the service manual it seems like the battery is you BEST hope. After that, it would be a loose/frayed/corroded electrical connection. The PCM is a $$$ if you have to replace it, especially if you get an OEM, instead of a reprogrammed unit.





Not sure if you are still having the issue, but if you have the access port, you should do some data logging. The data logs might be able to catch the APP and if the TPS is not matching.

If you would like to try a different throttle body, I have a spare one.

The other thing to consider is the HPFP. If you are going to do anything else, you will want to get a HPFP so you don't destroy the motor.

I see that you are in San Jose. I am just over the hill, in the Santa Cruz area, so you wouldn't need to worry about trying to get it mailed