I have a 94 GT that runs fine except when the motor's warm and you put your foot in it. Then there's a metallic rattling sound coming from the engine. It get's louder with the more load you put on the engine. Anybody know what I should check?
Check your timing. Sounds like a case of the "pings" or detonation. It could also be a header gasket leak. Retighten your header bolts, but if the gaskets are blown you will need new ones.
What is your timing set at?
What octane fuel are you running?
Kind of a stab in the dark here, but if you still have the factory h-pipe set up, then check the heat shields for the convertors. Perhaps one of the welds has come loose and its banging around.
finally checked the timing the other day and it's fine. I guess I'll try the heat shields next as the sound does seem to be coming from the area of the cats. the rattle isn't there when the engine is cold but the hotter it gets the worse the sound is when you accelerate.