My 91z's exhaust note changes to low pitched grinding sound after driving for about 15 minutes it's present no matter what gear I'm in. This happened about two months ago Now my cars running erratically my car loses power then gets it back, all my needles are bouncing around. At a stop I have to step on my brake pedal harder as it loses power, then the pedal stiffens back up. There is a regular timing to the car losing power,all my gauges bounce around in rythmn with it. You can actually hear the dip in power. Also my fuel economy went from 17 mpg to 13 mpg and i recently failed smog. This car was running well about six months ago and now it's just falling apart. Car was given a tune up about five months ago. Don't have money to take it in. Would make me feel a little better knowing what's wrong. Thanks for the help guys.

 

For starters, I'd suggest getting your alternator checked out.

 

Well, I'm not an expert. But i have a hunch you should bring your car into a shop now, while it is running, then say tomorrow, when it won't start.

Matt