The GP (supercharged GM 3800) has developed a strange rattle/scraping sound. It comes from the passenger side of the engine compartment and sounds sort of like a loose heat shield vibrating against a piece of metal or metal blades scraping against metal. It only happens at 1,900 rpm under light/medium load, such as when slowly accelerating or going up a slight incline, and seems to happen more often when the engine is fully warm than when cold. The noise stops if you raise the rpm to 2,000 or drop to 1,800 and does not happen if you just run up through the rpm quickly. It can't be reproduced for any length of time when parked because it needs that load; I can be parked and hold the engine at 1,900 rpm with no unusual noise. And it is not speed/gear dependent: it happens at 35 mph on city streets or 65 mph on the highway. Also not dependent on A/C or heater operation as it happens with it both on and off.
I have checked for loose heat shields and cannot find any.
Any idea what it could be? I'm at a loss and will take it into a shop for diagnosis later this week if nobody here can help me nail it down.
I have checked for loose heat shields and cannot find any.
Any idea what it could be? I'm at a loss and will take it into a shop for diagnosis later this week if nobody here can help me nail it down.