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Q: 1999 Pontiac Grand AM runs rough and smells weird

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I took my 1999 Pontiac grand am v6 to a mechanic due to overheating. Befor he worked on it the car ran good but overheated every so often. Sometimes maxing out the temperature gauge. It also had coolant leaks. He replaced the intake gasket and it no longer leaks, but it now runs very rough and shaky. My head bounces off the seat it shakes so bad. It has a odd smell coming from the exhaust. I can't really explain too well what it smells like (something to do with coolant possibly?) it doesn't seem to overheat and doesn't leak a drop now. But the serpentine belt is shredding. Maby he didn't put it on right? I just hope my car isn't screwed. it can still hit 70 mph just fine though, while it's in motion at 60 mph I don't really notice it anything, it doesn't show any signs of dying, just rough running, shredding belt, and odd smell coming from exhaust. I just want to know what's wrong with it or if it's safe to drive if I replace the belt

My car has 170000 miles.
My car has an automatic transmission.

A: Hello. An engine running rough at idle coul...

Hello. An engine running rough at idle could be a vacuum leak creating the wrong fuel ratio for the engine to operate correctly. The smell is probably unburned fuel caused by the vacuum leak issue. The belt shredding could be an alignment problem. You may want to have the previous work double-checked to see if there is anything they can do to help. If you’d like, you could have another certified technician from YourMechanic come to your car’s location to inspect the rough idling and strange smell so that this can be resolved properly.

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