Backfiring
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From: St. Peter
Backfiring
Ok, i've always thought my truck ran a little rich, but now its starting to backfire more often it seems. It usually always happens if i have to slow down real quick, like for a stopsign, and theres some traffic coming a few blocks down, so i hit the gas, it will backfire just once, and then take off. I was under the impression EFI was under the impression that EFI wasnt supposed to do this. No check engine lights, the only codes i get are a 111 all clear. 119k miles, and it will only do it when the truck has been warmed up. Now i dont know if i'm going crazy, but i could have swore that it did it a couple of times when i was actually moving (like a 30 zone changes to a 55 zone) and have to speed up.
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From: Eastern WA
Sluggish engine performance, overheating/running hot, and the sound of a vacuum cleaner comming from the tailpipe while you have your foot into it are signs of a clogged converter. I have a suspicion that you are either not getting enough gas when you hit the pedal (same effect as a carbureted engine with a failed accelerator pump) or the timing is not advancing when you hit the pedal (old vehicles use a vacuum advance dashpot on the distributor, but of course with EFI on this vehicle you won't find it, the computer will address this). Is there any chance you could have a vacuum leak? Somehow, I think you're gonna be running some pinpoint test on a few sensors, beginning with the TPS. I assume the engine is in good tune (plugs, etc).
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From: St. Peter
Yes, the engine is very well maintained, plugs, filter, wires, frequent oil changes (like i usually try to do it between 2500, and 3k, but i think i actually wind up doing it alot sooner somtimes just for somthing to do). If i had a vacuum leak, wouldnt that cause a lean condition, because i'd be taking in more air than the computer thought?
Post Fiend
Joined: Feb 2003
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From: Eastern WA
Vac leak = lean, but depending on the severity of it the computer may compensate for it. Does it stumble/hesitate too?
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From: St. Peter
YESSSSS! LIke when you floor it, backfires, and hesitates for like 1/2 a second the starts to crank out
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Post Fiend
Joined: Feb 2003
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From: Eastern WA
I'll stand by my earlier post then. Kinda tough with no codes, but I'd begin by running pinpoint tests on the TPS and the MAF. I'd also make sure there are no vacuum leaks. I assume too, that you've checked for KOEO, KOER, and CM codes, right?
Last edited by CowboyBilly9Mile; Aug 27, 2004 at 01:02 AM.
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From: St. Peter
Yep, and nothing for all 3 besides the pass code, I have the ford shop manual on cd, so i'll check out the tps and the maf for pinpoint codes ont that, thanks a bunch ,so far, you've been a great help both of you!
I've acutally been waiting for some codes to come on, so i would know what is wrong.
I've acutally been waiting for some codes to come on, so i would know what is wrong.
Post Fiend
Joined: Feb 2003
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From: Eastern WA
I forgot.......I would also check fuel pressure at the rail, both engine off and engine on, to rule out a weak fuel pump. However, usually a weak fuel pump is noticed at high engine RPM and evidenced by cutting out or low on power. The check is quick and easy.
By chance, do you have EGR on this rig (applies only to rigs originally sold new in CA)?
By chance, do you have EGR on this rig (applies only to rigs originally sold new in CA)?
Last edited by CowboyBilly9Mile; Aug 27, 2004 at 01:10 AM.
