back fires

[jons87mj]

my 88 4.0 auto 4wd back fires atleast 1 aday

and i don't know why :dunno:

any help would be apprchated

[Eagle]

How old is the oxygen sensor? If it's old, it doesn't respond as quickly as it should to changes in the fuel/air mixture. When you let off the throttle, it allows too much gas to keep flowing, the engine doesn't burn it, so it does down the exhaust and burns in the catalytic converter.

 

Backfire.

[jons87mj]

thanks ill just get a new one because the one thats in it came on the truck

[JeffN]

low fuel pressure can cause it to go real lean and detonate and that is very bad

[airspeed]

My sons 96 4.0 had an incredible back fire from a cracked exhaust header, this wasn't a little pop, we are talking a major ka-boom. Cars would pull over to the side of the road and people would come out of their houses.

The crack was just above the O2 sensor so it must have been tricking the O2 sensor into a lean condition and dumping too much fuel.

[cruiser54]

WHEN does it backfire? On the gas, off the gas, idling?

[jons87mj]

It only does it when it does it right after you let of the gas