My 2001 1.8 a4 has just started making a loud fast pinging (clicking) noise out of the back of the engine block durring a warm idle when the engine oil temp 250deg.it's very slight at startup. I reseached and though this could be sludge so I bought a oil pressure guage and ran the test. I have 1.6 bar at idle and 4.0 bar at 2000rpm just after starting the engine, however after getting to operating temp 250deg.My idleoil pressure is still 1.6 bar but at 2000rpm it falls to 3.0 bar whichI think is probably just becauseoil runs smoother at higher temps.Just to be safe I did 2 oil changes using 1 quart transmission fluid and the rest 10w40 dino oil and ran the car 10 minutes each time.The oil was really dark the first time and a little less dark the second.Finally I put in 5w40 syn. and a k&n oil filter. Still the same pinging. I should also tell you that I had the p0411 error code (Secondary air injector incorrect flow) message come up a few weeks before this started. Could it be the SAI, Oil Pump, Cam tensioner even EGR? I can't figure this one out. Can someone else out there who has been able to fix this problem tell me what they did and what I need to do to get my baby purring again?

Thanks

 

If its the top/back of the engine I would guess the cam chain tensioner is the problem