Car is not responding well,anyone have any clue ?

[ahmedi80]

hello
i have an 1996 316i compact ,i just replaced the motor with an 1993 M42 1.8 motor with my old gearbox and old electric circut,i was imagining to get a much better preformance ,but i am having a problem with the car response now ,when i hit the gas the car takes sometime to accelrate as if it is not breathing well ,
Can anyone help ?

[pnosker]

If you're using your old ecu you could be having issues due to different programming.

[cooljess76]

What caused your old motor to fail? Possibly a bad or clogged catalytic converter. I'm assuming that you cleaned or replaced the air filter, did you happen to notice if it's running rich? I'd check your plugs for buildup and also for proper gapping appropriate for the m42 engine. Make sure there's no leaks downsteam of the AFM as well as any vacume leaks or leaks around the valve cover or headgasket. Now that I think about it, did you use the old DME(ECU) for the m43? You might need to reprogram or swap it with one for the m42.

Edit; went to wash my hands and Patrick beat me to it. +1 on the ECU.

[pnosker]

Yeah, you definitely would need a new ECU; the M43 is only 2 valves/cylinder so the curves will be way different as will the timing.