Why is it backfiring?

[jeryst]

I was driving my 73 Challenger today, and it started doing something that it never did before. It ran great for a while, then, every time I would let off the throttle, it would backfire through the exhaust. Didn't seem to run bad. I stopped, and it idled fine, shut off and started fine. Got back on the road, and it still backfired every time I let off. I was close to home, so I just put it in the garage.

Anyone have any idea why it would do that?

[360 'CUDA]

Timing too far advanced?   

Streching timing chain or loose/broken distributor, camshaft gear ect
Bent valve/pushrod/wiped camlobe/ lifter

Hard to say

[Chryco Psycho]

usually it will be a leak in the exhuast system allowing air into the pipes & causing combusion with the rich mix as you let off the throttle

[loco340cuda]

This could be caused by a few different problems as mentioned already.

I have had the same problem that you mentioned when the header burned the spark plug wire and it was arching from the header to the spark plug wire.  If you have headers this would be one more thing to check for.

[MEK-Dangerfield]

This could be caused by a few different problems as mentioned already.

I have had the same problem that you mentioned when the header burned the spark plug wire and it was arching from the header to the spark plug wire.  If you have headers this would be one more thing to check for.

I've had that happen, but it was more of a miss than a backfire in my case.

I really have no other suggestions here. 


  Mike

[ted]

a bad spark plug or bad plug wires

[RusTy/SE]

Same thing happened to me years ago on my first Challenger and it turned out to be a burnt valve.

Russ