Suddenly started to run rough..............

[Hedgehopper]

I went to the TVRSS Open Day (excellent by the way) and had a great run home with no problems.

Next time I used the car, about two weeks later, everything had changed. The engine has a slight 'beat' to it at idle and when driven hunts and surges badly. From about 2500rpm onwards it seems fine, although this might be the sheer momentum of the car smoothing things out. Performance does not seem to be affected but from 1000 to 2000 in any gear the car is very hesitant to the point that there is no desire to drive it.

I have checked the plugs and they are all the same colour and not wet. I have tried the car with and without extenders and with old but good distibutor cap, rotor arm and plug leads.

I haven't as yet bought a new coil or changed the ignition amplifier.

Anyone out there got any ideas? Help will be appreciated.

[bluezeeland]

Stepper motor cleaned ?

[QBee]

Sounds like an air leak between AFM and pistons to me. The ECU is trying to adapt the fuelling to messages from the AFM, which is not actually measuring all the air getting into the engine.

[ESDavey]

Try driving with the AFM unplugged ... You will soon find if this us the duff part

[Hedgehopper]

Thanks for all the replies guys.

I have sprayed WD40 around the plenum area but no increase in engine speed. As suggested, I have run the car with the AFM unplugged and it runs even worse. Presumably this means that the AFM is working?

Will try the car tomorrow with the stepper removed and the hole plugged.