won't stop backfiring.

[littleblackpsycho]

Last year alI through the whole summer my truck ran fine then without any change it one day started to backfire out the exhaust. It's been about 8 months and I still haven't figured it out. It seems to idle fine and you could probably drive it but when ever it gets down to the 800 to 1000 rpm range it starts backfiring. Any help would be appreceated.

 

[sly dvl]

Re: won't stop backfiring.

Checked your timing?

 

[kentuc]

Re: won't stop backfiring.

If it`s not your timing,might be an exhaust valve.

 

[littleblackpsycho]

Re: won't stop backfiring.

Timings good unless the balancer slipped.

 

[Don W.]

Re: won't stop backfiring.

Cap, rotor, and wires. Sounds like cross firing to me. Good place to start anyway.

Timing, unless it's way off, shouldn't cause backfiring.:2cents:

 

[littleblackpsycho]

Re: won't stop backfiring.

distributer,cap rotor,plugs and wires all have about 1,000 miles on them. My mods are all the saftey mods, 50lbr's, 20g, tuner pro, ostrich. The only thing that I can think of is an intake gasket or maybe the egr valve would that be possilbe?

 

[Don W.]

Re: won't stop backfiring.

distributer,cap rotor,plugs and wires all have about 1,000 miles on them. My mods are all the saftey mods, 50lbr's, 20g, tuner pro, ostrich. The only thing that I can think of is an intake gasket or maybe the egr valve would that be possilbe?

I guess what I'm saying is at least check the cap and rotor. Look inside the cap for "carbon tracking."

What's funny is you say it backfires only in the 800-1000 rpm range? That's kinda weird. If correct maybe some sort of fueling issue. TPS?

Old trick, mentioned here often: Run it in the pitch dark and look for sparks. If things are bad you'll see 'em.

 

[ircwet]

Re: won't stop backfiring.

Bad gas?

 

[littleblackpsycho]

Re: won't stop backfiring.

I changed the gas and I remember checking the cap rotor and wires during the winter. But I'll run through them again today.

 

[littleblackpsycho]

Re: won't stop backfiring.

If it idles in the 10.0 afr range it doesn't backfire as much once every 30 sec. and it's very sparatic but the leaner you go the worse it gets with faster repetitions.

 

[sly dvl]

Re: won't stop backfiring.

Are you talking about a "backfire" or a "mis-fire". I really can't see it only backfiring @ idle. That just doesn't make sense...

 

[littleblackpsycho]

Re: won't stop backfiring.

It's backfiring I promise. I drove it up he drveway today and as long as you are on the gas it clears up and seems like it would drive fine but as soon as you let off it does it backfires. Cap and rotor seem fine tonight I'll try to run it in the dark try to find some arcing or something.

 

[Don W.]

Re: won't stop backfiring.

OK, let me ask if it's backfiring through the throttle or out the exhaust?

 

[gkrcr882]

Re: won't stop backfiring.

10.0 sounds pretty rich.....from a scantool and 5 gas analyzer, my Ty was at stoich (14.7:1) at idle, with a constant 725 RPM desired. Sounds ignition related however...check to be sure the wires are not resting on any hot parts of the engine, or any spots where they could rub through the insulation and short to ground.

 

[littleblackpsycho]

Re: won't stop backfiring.

It's backfiring out the exhaust. When you first start the truck it will run fine rarely backfiring idles at 1000 and 10 afr then when it gets up to temp and starts to idle down and lean itself out which I had it lean out to stoich before and it would idle and run perfect but now it would backfire continuosly in the 12ish range.

 

[bezerk]

Re: won't stop backfiring.

have you chacked your vacuum lines? or if you have a boostgauge.. what does it show at idle?