BMW E39 520i Auto Slightly Rough Running at Idle - Long Post

[taxboy]

I finally got to taking my 2001 E39 520 Auto (103 k) in because I had the ABS sensor changed & still got ABS + Traction warning lights when the car got hot. The indy initially rang me to say after plugging would need a new control unit & would take a couple of days to get. When I went back to pick the car up he said he had another look and noticed some oil in the loom & wondered if this was the problem so rather than spending a fortune on a new unit he had cleaned it out cleared the faults out road tested it and seemed OK. As I was going on holiday he said let him know how I got on. A day later sensor light comes on together with the engine fault light & whilst on holiday the car gets very lumpy at idle - and cut out once whilst stationery.

Car went back to the indy who plugged it in and it was telling him that I had a whole list of issues - all cylinders misfiring, coil fault feed problem from DSE, thermostat. He said these couldn't all be correct as the engine probably wouldn't have run with all these faults. Also still some oil in the loom. He has therefore ordered me a loom from a breakers and will fit the the new control unit at the same time as he says that if the unit gets contaminated with oil then the warranty on it will be invalid & doesn't want to risk this. Once these have been fitted hopefully either the running problem will resolve itself or he will be able to diagnose specifically the problem.

He fits the control unit and about to fit the loom when he noticed that it had a broken plug so repairs the plug, clears the fault codes and then replaces the thermostat as this was then the only fault showing.

He cleared all the fault codes and replaced the thermostat as this was the only fault now showing & the car ran brilliantly for 2 days. Then ...... at idle it stated to feel slightly lumpy (initially I thought it was me being oversensitive) until the engine light came on and at idle intermittantly it ran slight rough, I can stop this when it happens by revving the engine to approx 2,00rpm for a couple of seconds and then it goes away

Car has been back & according to the diagnostic he reckons its a manifold air valve problem - so any ideas if this will cure it. I'm starting to get a little worried that the engine is slowly being rebuilt in an effort to cure this so any thoughts from the experts please

[Renn Sport]

A friend of mine had a similar issue and after spending 1k never sorted it.
Doesn't mean you will have the same thing but hey.. It sounds like you in for a hard slog... I hope you get it sorted. Faults like these drive me nuts.

[taxboy]

Thanks for your post - I guess its the way with modern cars in that you plug in the computer & see what it tells you. My only concern is that as one fault gets cleared it then decides that something else isn't right