About three months ago I started to noticed when getting off the freeway a slight overlapping knocking noise that I have pinpointed to the (above) cylinder next to the timing chain and or the Vanos solenoid for which I understand in on the intake side of the head. I have only heard this noise six times in about three months, if I shut off the engine and restart the engine the sound is gone except for today.

I went away after several minutes, came back and noise disappeared, I probably won't hear it for another 2-3 weeks. If the Vanos solenoid is located near that cylinder is it possible it could be the Vanos solenoid causing this sound by not making any change to the cam timing from getting off the freeway? Perhaps when I get off the freeway the Vanos gets stuck and thinks I'm still at 3000 rpms when infact I'm at idle. I'm 95% certain the overlapping noise is the cam lobe slapping something.

Feedback needed and appreciated!

Regards,
Systemlord.

 

I take it no CEL? I got a CEL once in a while, with a slight decrease in power. After a few minutes, CEL went away, full power returns. Turned out to be the intake VANOS. Seems there is a way to test them. I'm not sure how the test works, but it was my understanding the tech removed the VANOS and applied electric power to it and measured how much it moved. Hope I'm making sense here, as I believe it's nothing more than a solenoid. Maybe another member here will post how to test it..

 

No CEL, it doesn't occur long enough to get a CEL. Sometimes when I accelerate hard only while in third gear rpms rise quickly from 3000-5000 with no increase in acceleration, kind of like spinning you're wheels. It doesn't happen all of the time. Occasionally at idle the rpms rise above 1300 rpms then suddenly drops back down to idle, that is a rare event though.

Where is the VANOS solenoid located?

 

Driver side, sticking out from the end of the cylinder head. About as big around as a beer can. I think the n14 has one for the exhaust, the n18 has two for exhaust and intake. There are some threads around about replacing them (with pics), will look if I can find them..