Hi folks

Have an '01 525i Sport with steptronic. Picked up with a couple of faults which seemed to have been fixed. Cam sensor, climate control hedgehog and wheel sensor. But..

I noticed a couple of times in traffic that sitting with it in drive and foot on the brake it would gain a shudder. Drive off and it would clear for next time.

Today I got stuck for a bit - stop/start - the shudder got far worse and became noticable as a misfire and uneven running at idle.

I parked up for a couple of hours and all seemed well driving normally. Pulling in to a car park the misfire returned and now won't go away.

Don't seem to have lost any coolant and the temp stayed rock solid at 12 o'clock so guess head gasket is less likely.

Parked up for the night now. Any suggestions as to the next checks please?

Roy

Oh dear, these things are always a right pain in the sit down bits to find but are then can be relatively easy to fix.

Try taking it to a garage who can carry out a diagnostic check on the car.  You may be in luck and have a fault code stored which may point to a crank sensor, maf, O2, coil pack or similar.

Could be something simple like a knackered spark plug but it's tracking it down is the problem.

Have a quick look at the plugs, see if there are any black arc marks on them ...... a bit of a long shot, but the caps have been known to degrade and allow the potential to travel down the outside of the plug to earth.

Andrew is correct in what he says of course, looking for fault codes is always a good start.....but if you want another "quick look", one I suffered a couple of years ago, that didn't lead to a fault code being generated, but did lead me a merry dance, was a perished rubber hose between the air filter and the inlet manifold, it looked perfect from the top, and was split underneath.

That caused the car to "missfire" just as you tried to pull away, but would be perfect after that, and of course the split was opening up as the engine "moved sideways" as it picked up, and opened the split to allow a bit too much air in ......... after the sensor.

Good luck

Diags and a smoke test showed up a leaking breather pod for the back 3 cylinders.

The misfire was in fact 4,5 & 6 being shut down to avoid damaging the cats. Being replacing on Thursday