For some reason my truck likes to backfire and sputter at random. It will run good for a couple days then out of nowhere it will act up sometime for 5 mins or sometimes till you turn it off. The backfire sounds like its from the exhaust but not 100% sure. Im thinking its either a fuel issue or something has to be loose for it to be just temporary. The motor was just rebuilt 1500 miles ago and it has plenty of fuel in it so im stumped.

 

i had the same problems, has it done it since you rebuilt it?

 

It started the problem at 1400 miles after the rebuild and at first it would only do it for a few seconds and it would go away for 3-4 days, now its daily.

 

carb or fuel injected engine?

 

check your exhaust valves' adjustments- if they're too tight, the valve and seat will get too hot and can cause an afterfire (popping out the tailpipe) as can a rich mixture and an exhaust leak.
Incorrect timing can sometimes cause an issue like this as well... as can a wiring issue (loose or corroded connector for instance) between the distributor and igniter.

 

i was definitely thinking a timing issue, I did the timing chain in my 86 pickup 22r,and even the slightest bump with the distributor would cause it to backfire, run rough obviously until I readjusted the distributor and tightened it back up. Also bad spark plug wires arcing out could be the cause of this, run the truck at night and pop the hood, see if there are any wires sparking between the coil/distributor, or distributor/plugs.

 

When does it happen? acceleration? deaccel? coasting? maintaining? List some more 411 guy, vague post make it difficult to offer insight.

 

mainly on acceleration it starts whether its warmed up or not. When it does it the tach starts bouncing around like crazy when I put my foot on the pedal and it sounds like the motor is scrambling. Also it happens at just about any rpm and sometimes comes out of nowhere and will be gone in a few seconds, but its rapidly appearing more.

 

Valve Adjsments prob wrong? Jump timing?

 

I'll watch this post I have know idea, but would like to know what it is and how you fix it.