I had a similar problem before and it was the throttle body sticking. A second hand eBay bargain later and it ran perfectly again. Starts ok but the response to the throttle is to momentarily rev a bit then collapse back to idle. EML and engine lights on. Is this a known problem please chaps? Thanks.
M54 Fly by wire will not rev beyond idle. Fixed now!
- Thread starter motco
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Just a guess - but it sounds like a VW Golf TDI - this is also a drive by wire engine, and has a brake-operated switch, operation of which cuts the engine back to idle. With the brake pedal held down, it idles normally, but when the throttle is also pressed, the revs rise a little and go no further. I bet a BMW drive by wire engine has a similar safety device - if the throttle sensor failed to give full throttle, the driver would naturally hit the brakes, when this switch would save the day. I would have a look at the brake pedal, and disconnect the switches - one will be for the brake lamps, and perhaps there is another as a safety device. I do not know if the EML light would react to such a fault, but assuming there are no air leaks in the inlet bellows, a code reader would be handy.
Thanks Mike, I have yet to read the error codes but as I said above, I had this before and a replacement throttle body fixed it, but given the cost of those I baulk at speculative buying. If I could get the car to my local indie I'd ask him to run his test gear over it but obviously I can't. I'll get the ccodes and if the pedal is mentioned I'll check that. The brake certainly disengages cruise so there must be more than a brake light switch.
Funny business! I read the code (P1632) which refers to throttle adaptation process failure which was happened before. I then cleared the code and started the engine. It ran perfectly so after a short blast along a quiet country lane, put it back in the garage vowing to use it more often. I shall not be too surprised if the fault recurs but I have the OBD2 adapter in the glove box in case it needs clearing again.