TripleM, I've had several isuzu 3.2/3.5's in the family. I also owned a 2002 isuzu rodeo 3.2L LS 4x4. If this knock was an oil related concern (connecting rod knock, etc..) the engine would have died a quick death long ago. The #1 con rod bearing is what goes first on these engines from oil starvation. Once an audible bottom end knock is heard, she's done. There are no hydraulic valve lash adjusters on these engines, so it's not 'lifter tick' you are hearing, although this direct acting, shim and bucket adjustable valvetrain is inherently tappy sounding (sewing machine rythem). A loud rap at idle only is typically a worn timing belt tensioner (unlikely on a 2002). Some ping under hard acceleration is typical on these engines. Certain fuels, ambient conditions and driving habits make it worse. I guess I was lucky as I never had a ping with my 2002. You could try a decarbing on it, but I doubt it will yeild much. An oil system cleaner certainly is not a bad thing, but I doubt that will do anything at all for this issue. In the event you have not discovered this, these engines can consume oil at an alarming rate. Oil level checks at every fuel up are a must for long-haul trips.
Joel
