am i being naive ?

[newbieUK]

I heard that when swapping throttle position sensors on the p38 the car had to be hooked up to the testbook to reset the zero throttle position.

I swapped mine out a few days ago, and after an initial few hours of over revving and fast idling, the car appears to have sorted itself out is now idling as normal.

Can the BECM teach itself and recalibrate itself automatically, or am I just being naive and disaster is lurking just round the corner when i least expect it.

Should mention that the car is 99 with the THOR / Bosch engine.

Any assistance would be grateful.

[David Sparkes]

What you have experienced is the wonder of adaptive fuelling, resulting from closed loop running.

Simply, the output of the oxygen or lamba sensors in the exhaust is fed back (the closed loop) to the Engine ECU (not the BECM).

The ECU changes the fuelling so the amount of oxygen in the exhaust is 'correct' (as laid down in the fuel map).

Thus the fuelling is adapted to changes in the running condition, which could be new sensors (MAF or Oxygen), or changing atmospheric conditions, such that you might experience moving from Aberdeen to the Thames Valley.

If you wished to reset the ECU to it's start position for some reason, then you would need a Testbook, or Autologic, or Rovacom, etc, but what you have done is perfectly valid, and the poor running period is reassuring, in that it tells you that your new MAF is giving different (correct) results compared to the old one, thus justifying the spend.

Hopefully you will find both better running and increased mpg as a result.

Cheers.

[newbieUK]

What you have experienced is the wonder of adaptive fuelling, resulting from closed loop running.

Simply, the output of the oxygen or lamba sensors in the exhaust is fed back (the closed loop) to the Engine ECU (not the BECM).

The ECU changes the fuelling so the amount of oxygen in the exhaust is 'correct' (as laid down in the fuel map).

Thus the fuelling is adapted to changes in the running condition, which could be new sensors (MAF or Oxygen), or changing atmospheric conditions, such that you might experience moving from Aberdeen to the Thames Valley.

If you wished to reset the ECU to it's start position for some reason, then you would need a Testbook, or Autologic, or Rovacom, etc, but what you have done is perfectly valid, and the poor running period is reassuring, in that it tells you that your new MAF is giving different (correct) results compared to the old one, thus justifying the spend.

Hopefully you will find both better running and increased mpg as a result.

Cheers.

Cheers David, had a horrible image in my head of being stuck in the middle of no-where due to a £30 sensor !