P0101 code and VERY rough running

[Leon R]

My 01 Proton started to run really rough. I have to keep playing the gas pedal to keep it running. It sounds like it is running 3 cylinder and smokes like it is RUNNING VERY RICH. Eventually it would show P0101 code. Sounds pretty straight forward, only it isn't. I have since tried two other junk yard MAS sensors with exactly the same results, so it is very unlikely that I am looking at THREE MAF sensors with the same problem.

Thinks that I have tried/checked:

Two other uses MAS's
Compression
There are 12V and 5V at the sensor with key on
Ground is there when ECU is turned off, but whe ECU is on, it creates some resistance (around .3 ohm, just enough to no register continuity)

Any other ideas?

[Y33TREKker]

Fuel pressure regulator and fuel filter. Two relatively easy items to replace anyway.

[Leon R]

I know fuel filter fails by clogging up and making you run LEAN, but what about the FPR? Does it typically fail by reducing pressure or increasing pressure?

[Y33TREKker]

A failing FPR has been known to cause both just because of erratic fuel flow quantity. It's been a somewhat common issue in VX's anyway, so if it's never been replaced on yours, it would be a good place to start.

I only have about 45k miles on my '01, and I've already had to replace mine due to rough running.