My wife's 2007 Mazda3 started running poorly and showing a P2177 and P2187 code. The car runs great while it is cold, but after it warms up, you can feel a slight miss under light acceleration, ie when the cruise is on going up a moderate hill. If the car is turned off warm for at least 5 minutes, the CEL comes on the first time the car accelerates. The usual code is P2177.

After reading up on the fault, I replaced the MAFS, the fuel ratio sensor, and the purge valve. None of this helped.

Tonight, I took the car out and tested the new components with my laptop hooked up to it. When the car was missing, the voltage to the air/fuel sensor was going crazy. When the car was running smooth, the readings stayed smooth.

Any ideas? Can a bad ECT do this? It is odd that the car runs flawlessly until it warms up. Help!


David Nolen

 

Did you check all the wires/pins on the MAF? It's pretty common with the 3 for the wires/pins on the MAF to get broken/loose, especially the ground on the MAF. This is especially true if you've replaced the stock intake with a CAI as the MAF wiring harness is tethered to the battery box. Unless it's released it can strain the wires when the engine torques during hard acceleration.

Anyway I'd check out the harness to make sure everything's good with it. Also check out the engine mounts.