Well, here's the plan so far:

Step 1: Do a proper electronic diagnosis with DIS/INPA instead of the handheld I used for the preliminary diagnostics.

Step 2: Swap VANOS solenoids side-to-side to see if the problem moves from Bank 1 to Bank 2. If so, hopefully I'll just have to replace a solenoid.

Step 3: If the problem isn't the solenoid, I suppose I'll have to rebuild the VANOS actuators themselves. Not fun on the V8.

Of course, this is all assumes that the advanced diagnosis confirms the original findings from the handheld.

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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)