I know I don't have one - If I had a source I'd more than willing to share it.
Based on experience, sometimes the obvious is most often overlooked - even if there is a manual in the glovebox, not that there may be.
Why guess? - that could get expensive. Or just watch your rpm's when driving and see if the tach is consistent with gear/rpm and illumination.
Member of the Dropped Valve Seat Club.
Replaced #4 Piston, Rings, Rod+Bearings, AERA Re-Manufactured Cylinder Head and a light Hone. Then CLEANED the hell out of everything.
40k+ miles, now jinxed?