350i misfire at 4,500rpm

[KKson]

Hi all, the 350i has been occasionally misbehaving for a few months now. Car starts first time and runs great. Once it warms up however if I floor it and run the revs up it starts misfiring at around 4,500rpm. I'm working my way through the usual suspects, temporarily swapping components off the 390SE, one at a time, in order to eliminate things. It's not the coil, HT leads, plugs, dissy cap or rotor arm. I've also double checked the timing and also the fuel pressure - all of which are good. The fuel pump is only a few years old and gives consistent good pressure.

Next on the list is the ignition module. If that doesn't resolve it then I've also got a spare ECU, full dissy and AFM to play with. Anyone got any other ideas I may have missed? Coolant temperature sensor and twisted wires? (cue Marks photo....). Cheers.

[Jobster]

Different car but had the same. Not the kind of guy that takes the easy, cheap but time consuming road. So changed everything including ignition module. Problem solved.

[mrzigazaga]

No pic Keith...its buried somewhere in an external drive..

Did you change the distributor on the 350i or was it the 390SE?....could be sticking bob weights....mind you if they dont get used for a couple of weeks they do start playing up...

[KKson]

Thanks for the replies. It was the 350i that had three fussy from Powers park, which I ditched as it was crap, and bought a good original serving hand unit. It could've the in weights. I do now have a good spare for the 390 so if ignition module doesn't sort it then I'll swap the dissy.

[mrzigazaga]

If the weights are sticking you could try some electrical contact cleaner...carefully remove the dust cap and spray plenty inside...leave for an hour before trying it...it sorted mine.

Cheers

Ziga

[KKson]

All sorted and rude health restored. I swapped the dissy out for a good working spare I'd used on the 390SE. Not sure if it was the bob weights or ignition module as I swapped the lot. It had obviously been playing up for a while as the new dissy gives me way better low rpm pulling and screams happily to 5,500rpm without a hiccup. Happy days.

[mrzigazaga]

...enjoy