For the last couple of weeks my 98 523 (2.5 ltr m52) has been running crappy at idle. I sprayed a bit of carb cleaner around the inlet manifold and the revs increased slightly - obviously needed a new manifold gasket then!! I've had this replaced today and tried the old carb cleaner test again - no leak, then why the bloody hell does she still idle like a bag of crap???? Idle control valve is likely a culprit but the thing is sometimes she will settle at idle perfeclty and I have to keep revving her to get the bad idle again, other times she will just consistently idle badly - does this sound like an idle control valve issue??? I thought they just died or can they just get a bit sticky? I disconnected the MAF and the idle problem went away, however after driving home with the MAF disconnected the idle problem returned. This might sound stupid but the problem always seems worse when I put her on my steep drive nose facing down <wtf??
Also there is an incessent rattle from the exhaust somewhere which started about 7-8 weeks ago as a little tinkling but now is a major rattle when the engine is started/revved. Last week I had a new hi flow Stainless cat, center box and rear box fitted not just because I thought it would aliviate this problem but because I had promised myself a stainless system for a while. The exhaust was a custom job and uses the down pipes from the original cat, is there anything in these down pipes that could cause a rattle - ie are they double skinned or something or can anyone think of a possible problem with the manifolds??? She had new manifold gaskets about 3 months ago. Just to let you know what the rattle sounds like, it really sounds as if a heat sheild is loose, but this isn't the case, all are in place firmly.
Any help appreciated