Engine Rattling

Hey there...been awhile, been too busy with my other mode of transportation (gs500), but recently my 2001 (75+K) has had significant loss of power. (going uphill biggest difference) I do the usual oil change, fuel filter, engine flush (dealer $$$$$) . Saw a slight improvement, and now i hear a rattling at low rpms. Asked the dealer bout it and he said just heat shield?? ehhh help. THanks in advance.

Possibly a plugged catalyst - causing high exhaust backpressure.

With high backpressure the hot exhaust gas gets trapped in the cylinder, and lowers the threshold for pre-ignition, or pinging - possibly the rattling noise you hear.

Makes sense too that when the engine is loaded (ie. going up hills) it would be worse, as the exhaust temperatures raise when the engine is under a load, and the pre-ignition would be exacerbated.

Is your engine temp raising? I would think that if your cat converter is plugged, the engine temp will raise.

OK sounds fixable . Easy fix or dealer job? Thanks

ohh forgot to mention, no no temp rising. At least that's what the gauge says.