I haven't posted anything about my 2002 4.6is in a while because I've actually been able to drive it instead of just work on it (109K miles, purchased in June 2015). Well, that all changed today and it looks like my record for not having to work on this thing will stand at 4 weeks.

It's been running great after I finished up some fairly major surgery about a month ago. That consisted of replacing the crankcase vent, intake manifold gaskets, oil separator, and all the associated vacuum and drain hoses. For good measure I also replaced the valley pan gasket, all 8 coils, and throttle body gasket.

I went to the drive thru at the bank this afternoon and heard a what could best be described as a rhythmic engine sound when I rolled down the window. I also noticed a very slight shudder when idling that wasn't there last time I drove it. The sensation was very similar to what it feels like when an ignition coil is getting weak, but hasn’t failed completely. I made a stop to run another errand and when I restarted it the Check Engine light came on (it wasn’t on until now). The slightly rough idle was still there, although at higher engine speeds everything seems fine. And of course the noise was still there.

When I got home and opened the hood, there is a distinct mechanical sound coming from the front of the engine. But it’s not a rattle - it’s almost more of a low pitched squeak. I also noticed that the engine would nearly stall every few seconds. That’s the source of the shudder I was feeling at the bank.

It reminds me very much of the failure pattern for the VANOS in an M52TÜ or M54 6 cylinder - the same dodgy idle and near stalling. Except on the I6, that goes away once the engine warms up. Even after it was fully up to temperature, the X5 was still having the symptoms. Having recently performed a complete timing chain/guide and VANOS service on a 2001 740i, the telltale sings are very familiar to me. The noise I’m hearing from the X5 is not the same as the 740 - and the 740 definitely needed chains and guides.

I understand that the code is related to the variable timing for Bank 1, but isn’t more descriptive than that. It’s pretty obvious that it is a timing problem because of the near-stalling. But I’m not really sure where to begin with diagnosis and repair.

It’s worth noting that roughly 1,000 miles ago I performed an oil service and replaced the valve cover and upper timing cover gaskets. While the oil was drained I removed the oil pan to check for debris that signaled failing timing chain guides (there was none) and visually inspected the chain guides. There were no signs of any trouble related to the chain guides.

Also, I back into my driveway and open the door so I can see where I'm going and to make sure I don't run over the grass. So I definitely would have heard this before if it had been going on for a while.

After doing a little reading online, I think I can rule out the cam position sensor, but might swap one with the 740 anyway - just to make sure. After that, I might check the VANOS solenoid. But if that’s not the problem, I’m not sure what to look for next.

Does anyone have experience with these symptoms who can suggest where I should focus my efforts at diagnosis?

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2002 X5 4.6is - Imola Red/Black (Sold)
2001 740i M Sport - Anthrazit Metallic/Black (Sold)
1998 M3/4/5 - Technoviolet/Dove (Sold)
2003 Z4 3.0i Sport - Sterlinggrau Metallic/Black (Sold)
2009 Mini JCW (The Wife's)
2015 i3 REx - Arravani Gray/Tera World (Daily Driver)