So since getting this 540/6 last July the ASC light would not go out when depressing the ASC button meaning the system was not ON.
I finally before bringing it to a BMW trained shop for diagnostic decided to try swapping the two throttle position sensors. The plugs do have slight differences in the cover but they do each fit on the other sensor..
This was in fact the problem.. Immediately the ASC light went out , the rough and surging idle I assumed was a sticking ICV all vanished and the engine performance noticeably improved though it wasn't really bad other than the idle issues... just much faster responsiveness to throttle.. Now I can drive carefree in Snow again and get on to other issues..
Thanks for that follow up. Don't you want to strangle the guy who did it?
If you can leave two black stripes from the exit of one corner to the braking zone of the next, you have enough horsepower. - Mark Donohue
It's an easy assumption that something is assembled correctly when we start a diagnosis. This is a good reminder that isn't always so.
I have a sneaking suspicion the M20 no start thread currently a few threads down has a similar problem.
If you can leave two black stripes from the exit of one corner to the braking zone of the next, you have enough horsepower. - Mark Donohue
Actually my mechanic made the same mistake. I don't remember what repair the E34 was in for. I picked the car right before they closed and noticed the ASC light as well as the idle. I was going to bring it back the next morning, but got to tinkering around at home and switched the sensors. Voila!!! I agree: BMW should have designed the connectors to be different so this should never be an issue.
USC Ralph - Long Beach, CA USA
1989 E34 White 525i (M20) 310,000m (Sold)
1993 E34 Black 525i (M50) 308,955m
1995 E34 Calypso Red 540i/6 (M60) 201,254m
1993 E34 Black 525iT (M50) 138,500m
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