325i Engine - Slight Running Issues

[Eddie1990]

I've swapped an M20B25 into my BMW E21, all seems well, apart from the following issues:

- When at idle, if the throttle is opened quickly, there is a slight delay/stutter/misfire before it catches up.

- When the throttle is opened and the closed, the revs drop below the idle for a second or so, before returning to normal.

- When the throttle is opened slowly, it revs up well enough.

I've had the plugs out to do a compression test and the plugs are very sooted up, so I'm assuming it's running quite rich?

It's also idling slightly high, about 1200rpm maybe?

Could this be the blue plug possibly?

[Speedtouch]

Did you let it idle for at least 10 minutes to enable base idle settings to be learnt? If not, disconnect either the battery or ECU and leave for an hour or so to reset the ECU then do the above.

Then switch off, then take it for a drive throughout the rev range. This ensures full data transfer from the EPROM to the processor.

Also check the blue temp. sensor:

http://www.e30zone.net/e30zonewiki/inde ... emp_Sensor

[minesapint]

Try reading this, particularly the sections on AFM & Adjusting the base idle settings & mixture.

http://www.e30zone.net/modules.php?name ... c&t=153524

[aimlessrock]

Sounds like you have an air leak... Do not touch the Afm until
You have properly checked.., the wikki has an excellent trouble shooting guide.

[reggid]

check for vacuum leaks firstly before adjusting something that might be already properly adjusted