What would cause backfiring when letting off throttle?
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Joined: Feb 2002
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From: Sapupla OK
What would cause backfiring when letting off throttle?
I have a basic L48 with hooker headers and true duals (with H pipe).
The car has run reasonable up to lately and I haven't done anything to engine
It seems to have developed a "miss" and when cold will backfire occasionally when letting off the gas.
My first thought was timing, I unhooked vacuum timied to 6 deg, per my Chilton's and it didn't run worth beans. took it out on road drove adjusted, drove adjusted and got a "best" setting that looks to be about 16 deg (with vacuum unhooked)
After this little exercise, I wound up with it pretty much as it was before I started.
Any thoughts would be appreciated
Ken (molchaser)
The car has run reasonable up to lately and I haven't done anything to engine
It seems to have developed a "miss" and when cold will backfire occasionally when letting off the gas.
My first thought was timing, I unhooked vacuum timied to 6 deg, per my Chilton's and it didn't run worth beans. took it out on road drove adjusted, drove adjusted and got a "best" setting that looks to be about 16 deg (with vacuum unhooked)
After this little exercise, I wound up with it pretty much as it was before I started.
Any thoughts would be appreciated
Ken (molchaser)
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From: Huntersville NC
Re: What would cause backfiring when letting off throttle? (molchaser)
I would get backfiring when letting up the gas when I had an exhaust leak. Worst case was a broken front pipe, but I also got some popping with small leaks around the mufflers or just about anywhere in the system.
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St. Jude Donor '09
Re: What would cause backfiring when letting off throttle? (molchaser)
All the above, possibly carb running too rich.
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Re: What would cause backfiring when letting off throttle? (Jughead)
Unburned fuel.
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From: Camden AR
Re: What would cause backfiring when letting off throttle? (OHSIXX)
Unburned fuel.
Maybe rich when engine burning cold (inefficient) and good when warm...I've had this problem and left it as is...
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Re: What would cause backfiring when letting off throttle? (6318)
I use to have lots of backfires. Then one day loss spark altogether. Installed new coil just to get going again.
Soon realized the backfiring was gone. Sorta puzzled me! :skep:
Soon realized the backfiring was gone. Sorta puzzled me! :skep:
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Verdad Gallardo
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From: VASS, NC, USA
Re: What would cause backfiring when letting off throttle? (OHSIXX)
I would check your spark plug wires AND your spark plug wire boots. Headers ususally run extremely close to plug wires, and especailly the boot ends. Just a tiny melt spot will bleed over spark, causing back fire when you let off. Pull them off, and inspect, one at a time, VERY closley. Just dont eye it. Check every inch, and bend the material as you look to look for heat cracks or burns
Burning Brakes
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From: Austin Tx
Re: What would cause backfiring when letting off throttle? (MELVIN)
I kind of like the sound of slight popping through the sidepipes as you decelerate...gives the car a nostalgic sound...I don't think it is anything to get concerned about. As long as you are not backfiring through the carb
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From: Waterloo ontario Canada
Re: What would cause backfiring when letting off throttle? (molchaser)
In stock car racing you see the cars going into the corners and flames comming out the exhuast, a real popping sound and it is caused by poorly adjusted idle circuits drawing fuel into the motor on deceleration.
In holleys it is the transfer slots being uncovered and dumping fuel.
In holleys it is the transfer slots being uncovered and dumping fuel.
