1990 pontiac firebird backfiring out the exhaust on deceleration. It is a 305 tpi

[kurt w]

automatic.? Here are the things i have done so far. Replaced spark plugs, plug wires, distributor cap and rotor. checked the air injection valve and air pump. Checked the timing. no obvious exhaust leaks before the cat convertor. The car does reek of fumes, smokes and runs a little rough on cold start up. I have been told it could be a bent push rod or valve. Any advise before i start leaning that way????? Thanks ~ Kurt ~

 

[BEAUTY]

its making that noise like an old ti-mi truck or something....when you step on the gas, it goes boom? lol

 

[GSD PAL]

Check the car for leaky injectors or anything that can contribute to a rich condition. After decelerating the ECM will command the injectors to decrease fuel. If there is any fuel vapor from an unburned mix then there is a high possibility of an ignition in the exhaust stream especially on cat equipped vehicles.

Pull the vacuum hose on the fuel pressure regulator and make sure that there is no raw fuel entering the vacuum line. If you see signs of fuel then the regulator is defective.

 

[Goatman]

Also if you have any leaks in the exhaust pipes in fornt of the muffler that allows air in on decell it may pop and bang ...