What causes an exhaust backfire or afterfire?

[justagt]

My speed density fox backfires through the exhaust ( I think it's actually called an afterfire but whatever).

 

[Jack's95gt]

If you have a high milage car, then check your timing chain. It may be worn and loose.

 

[svtpower]

hmm

Maybe timing?

 

[bt15]

Check your ignition and timing first. The coil is always suspect in this type of circumstance (relatively cheap and easy, too). Ignition boxes can exhibit this type of behavior when failed (or failing). I have seen all these culprits cause this kind of problem.

 

[fordguy87]

I'm actually having this kind of problem right now too. I have a new timing chain on, new spark plugs, new wires, msd coil and new distributor cap and rotor. What else do you think it could be... O2 sensors maybe?