Hi All,

I have a 2005 E61 530iA M Sport touring.

On a holiday to Belgium it was 'fed' water instead of fuel by a roadside gas station. The car broke down (not surpisingly) about 1km later. It then spent 4 days in a BMW garage in Belgium. They drained the fuel, reset the timing etc.
Upon returning to the UK it developed a mis-fire. This was diagnosed by my local BMW dealer as a broken coil (dropped by the garage in Belgium?). This seemed to solve all of the problems apart from a 'low' and erratic idle about 5-600RPM. The dealer said book it in AGAIN, at which point I have lost faith in the dealer.

What would cause this problem and why does it run almost normally on 98 fuel and roughly on 95?? Is it a timing/mixture problem? What can I do to solve this? Also, the exhaust looks a little sooty indicating a rich fuel mixture?

Any feedback really apprecitated,

Mint

I would be surprised if fuel grade would affect the idle but perhaps poor fuel quality might. Try running a couple of tanks of 98/99 octane through the car. Is the idle any different with the car in park/neutral than in drive?

First step really is to get the codes read out of the ECU to see what it thinks is wrong. I'm amused that you were told the timing was reset - there's nothing to adjust as its all electronic - there isn't even a distributor.

Yes the idle is lower in drive, I am guessing that is due to a bit of clutch 'drag'?

I have just filled up the car with 95 too....

Yes, agree about the timing. The Belgium garage also said the chain had jumped a tooth too and the jockey was replaced....my Flemish is poor so it may have all been lost in translation.

Do you recommend another trip to BMW to get the codes? The last time I went to the garage with it idling like this the service advisor said as there was no warning lights and codes everything was fine!! Despite the obvious sounds and vibration through the car...I don't want to waste another half day drinking BMW coffee and reading BMW magazines!!

The idle might be a bit lower in drive but the gearbox is quite clever and puts minimal drag on the engine when the car is stopped. But is the idle any less smooth?

The dealer's diagnostic equipment should be able to confirm that all 6 cylinders are firing evenly and correctly - unless you want to start throwing parts at the car I'm not sure where else you can start?