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Backfire On Tbi?

K

K5HIGH

1/2 ton status
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Dec 8, 2004
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harrison twp. mi.
Im driving home from work last night after getting all the power motors replaced for the pwr windows and tailgate and another problem arises. I step on it and it backfires, hesitates then downshifts and takes off. It was cold and has done this another time also when cold. what could the problem be? :confused: By the way its an 88 k5 w/350 tbi
 
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K5HIGH said:
Im driving home from work last night after getting all the power motors replaced for the pwr windows and tailgate and another problem arises. I step on it and it backfires, hesitates then downshifts and takes off. It was cold and has done this another time also when cold. what could the problem be? :confused: By the way its an 88 k5 w/350 tbi
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ANYONE??????:confused:
 
i'll take a crack at it....since the computer controls the entire air/fuel mixture, and backfires are caused by faulty mixtures, i can only assume one of ur sensors in the engine compartment may be failing and the cold temps cause it to show it's failure in a major way, by the back fire...no check engine light when this happens eh???

I would hook up a good scanner to your OBD port and check all the voltages on ur fuel system sensors and make sure one of them isn't giving bad voltage readings...that would be the only way to check, if theres no check engine light, you won't be able to get any feedback from a cheapy OBD code reader..
 
another thing to check would be your fuel pump also...again, i would think the check engine light would come on with any of these systems malfunctioning...esspecially if a fuel pressure change occured...
 
semper-k-five said:
i'll take a crack at it....since the computer controls the entire air/fuel mixture, and backfires are caused by faulty mixtures, i can only assume one of ur sensors in the engine compartment may be failing and the cold temps cause it to show it's failure in a major way, by the back fire...no check engine light when this happens eh???

I would hook up a good scanner to your OBD port and check all the voltages on ur fuel system sensors and make sure one of them isn't giving bad voltage readings...that would be the only way to check, if theres no check engine light, you won't be able to get any feedback from a cheapy OBD code reader..
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COULD AFTER MARKET EXHAUST HAVE ANY THING TO DO WITH IT? O2 SENSORS READING WRONG. NO ENGINE LIGHT ON THOUGH BUT WHO KNOWS THE PRIOR OWNER MAY HAVE TURNED IT OFF?
 
well, i guess that would depend on what type of exhaust you had installed...straight pipes? what type of cats? things of that nature...if the exhaust is refined any more or any less due to the system you have, it could cause a O2 issue and cause your computer to over or under adjust to reach the readings it's looking for...
 
semper-k-five said:
well, i guess that would depend on what type of exhaust you had installed...straight pipes? what type of cats? things of that nature...if the exhaust is refined any more or any less due to the system you have, it could cause a O2 issue and cause your computer to over or under adjust to reach the readings it's looking for...
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FULL LENGTHS STRAIGHTS AND 2 FLOWMASTERS THEN STRAIGHT TO THE BACK
 
hmmmm...yeah, if ur not runnin a cat, i would certainly expect a problem there...you may have to tweak your computer with a straight system...i would contact a muffler shop and ask if they do computer adjustments for aftermarket exhaust systems and types...
 
semper-k-five said:
hmmmm...yeah, if ur not runnin a cat, i would certainly expect a problem there...you may have to tweak your computer with a straight system...i would contact a muffler shop and ask if they do computer adjustments for aftermarket exhaust systems and types...
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YEAH SO I FIGURED SO MUCH. PROBABLY HAVE TO GET A TUNER FOR THE COMPUTER SEEIN THAT I WILL MAKE OTHER UPGRADES IN THE FUTURE. OR CHIP? NOT SURE HOW MUCH THE COMPUTER CONTROLS IN '88 IM SURE NOTHIN LIKE THE TECHNOLOGY NOW LIKE IN 01 SS LS1. ANYWAY AROUND ANY OF IT?
 
you really think not runnin a cat would cause that problem? is it a backfire through the TB or the pipes? the O2 is before the cat so i dont think the running or not running a cat would change the fuel mix. How ever if there is no cat (wich is designed to get real hott and burn any excess unburn fuel) this might cause a back fire,

Also when the engine is cold it runs in a closed loop mode, wich should be a rich condition=more fuel= more likeley to back fire when you romp on it when its cold
 
Yes...a permance chip would offer you a fix...you would have to contact summit or someone like that who will have a helpfull tech person to speak with...tell them the mods you have already made and what you have planned for the future and they may have a chip designed to fit ur needs...i would certainly expect there's something out there for folks running straight pipes...
 
surpip said:
you really think not runnin a cat would cause that problem? is it a backfire through the TB or the pipes? the O2 is before the cat so i dont think the running or not running a cat would change the fuel mix. How ever if there is no cat (wich is designed to get real hott and burn any excess unburn fuel) this might cause a back fire,

Also when the engine is cold it runs in a closed loop mode, wich should be a rich condition=more fuel= more likeley to back fire when you romp on it when its cold
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I was thinking that too...I know some systems have O2's before and after the cat...i wasn't sure if the OBD I system used that set up or not...
 
I only know the more you let out, the more you gotta let in! you're gonna have to make some sort of TBI upgrade to match your new exhaust flow...i just can't tell ya exactly what that would be...other than rip it all out and carb it w/ a truck avenger or qjet...
 
semper-k-five said:
I was thinking that too...I know some systems have O2's before and after the cat...i wasn't sure if the OBD I system used that set up or not...
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ITS A POP THROUGH THE THROTTLE BODY I THINK CUZ ITS NOT SUPER LOUD.
 
if it's through the throttle body, then ur system is leaning out...probably cause of the rich flow through straight pipes....
 
well there is a pretty big difference in waht could be wrong if it is through the TB or the exaust,

oh and turn your caps off:D
 
The best way to keep this from happening is to not romp on it when it's still cold. That is a bad idea whether you're running straight pipes, cat, carb, TBI, with chip, or without chip.
 
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