Has anyone had this problem? My (chipped) 320d coupe has a problem with its EGR valve or something associated with it.
Fuel economy was down and it had a major flat spot from 1700 - 2200 rpm.
Bought an EGR bypass valve and WOW.. it flew, pulled like it should through the rev range. Only thing is, engine management light came on and wouldn't go out.
I cleaned out the original EGR valve and it seemed to open when pressed hard with no sooty deposits. Put it back on the car and the flat spot's still there.
Any ideas on what else to check? Not sure what the small pipe does that attaches to the nipple on it.. could it have a leak? would this effect it? Although the flat spot came back, the engine management light has now gone out. Grrrr!