Gun shot backfires?
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Gun shot backfires?
My 1993 F250 ext cab 4x4 with 351 - 5spd is still letting off super loud backfires when I gear down and when I accelerate hard in say first gear and put in the clutch. I changed plugs, cap, rotor, wires , air filter, pcv valve, fuel filter, breather valve, checked timing -at 10 degrees. Wires are on proper plugs.
When I first did tune-up I didn't have my plug gap tool so just put in plugs as they were but it was still giving the occassional backfire, so I pulled the plugs checked and regapped them to 0.044", they were all around 0.038" out of the package. I rechecked timing, still at 10 degrees, but the gunshot backfires are even more frequent now with proper gap of 0.044",(which is wider than before)????????????????????
Oh and I have a new flo pro 3" muffler and pipe with the old gutted cat, with no leaks, any thoughts, maybe coil???????????? How do you test coil??
Thanks mat
When I first did tune-up I didn't have my plug gap tool so just put in plugs as they were but it was still giving the occassional backfire, so I pulled the plugs checked and regapped them to 0.044", they were all around 0.038" out of the package. I rechecked timing, still at 10 degrees, but the gunshot backfires are even more frequent now with proper gap of 0.044",(which is wider than before)????????????????????
Oh and I have a new flo pro 3" muffler and pipe with the old gutted cat, with no leaks, any thoughts, maybe coil???????????? How do you test coil??
Thanks mat
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So will adding baffles to the system help? The popping sound of the exhaust gearing down doesn't bother me, it's the occasional gun shot backfire that I want to remedy. Is it caused by unburnt fuel being forced into exhaust system?
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I have a 1970 Torino with a 460, no cat, dual 2.5 flo pros, same muffler as my truck and I get the popping exhaust sound as I gear down using high revs, but never the loud gunshot backfires I get from my F250, that's why I thought it was something other than the lack of backpeessure
mat
mat
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Thanks for the replies, so if I add baffles to the exhaust, in front of my muffler will this take care of the super loud backfires, or will the baffles just get rid of the usual popping sound I've heard on many cars with hi flow exhaust, like my Torino with no cats and two flo-pros??!!?
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baffles will be the same as putting a muffler on only restricting it and adding enough back pressure will get rid of it but then you may as well have kept the stock exhaust.......this could be wrong but a cat could help
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Cargo Master
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From: Arcadia, Fla
Sounds like your running rich. Is this EFI or did you swap to a carb? If its EFI, pull the codes and see what code are present. I doubt a cat would help in totaly ridding the afterburning but would help in burning up the unused(wasted) fuel. Now if it's a carb setup, check your power valve, that might be leaking fuel.
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Could just be just late ignition timing, very late due to setting it with the jumper in place and a loose timing change. Even that should not create a back fire though, shouldn’t be enough fuel in the system to backfire at that point.
How does it run/start? Got any power or doggy?
Did you pull the spout when you checked/set the timing? Install the right heat range plugs?
Either way sounds like your system might not be returning to an "idle mixture" like it should as fast as it should when you back off the throttle to slow down, or shift, spewing some fuel into the exhaust system. bad sensor or one or more leaking injector's etc etc.
I'd start by check it for trouble codes, KOEO and CM but should also run the KOER test and see if something shows up.
And run a fuel pressure test, does it hold pressure like it should? or just drop to zero once the pump stops?
Take it for a ride in the dark, any of the exhaust glow red hot?
How does it run/start? Got any power or doggy?
Did you pull the spout when you checked/set the timing? Install the right heat range plugs?
Either way sounds like your system might not be returning to an "idle mixture" like it should as fast as it should when you back off the throttle to slow down, or shift, spewing some fuel into the exhaust system. bad sensor or one or more leaking injector's etc etc.
I'd start by check it for trouble codes, KOEO and CM but should also run the KOER test and see if something shows up.
And run a fuel pressure test, does it hold pressure like it should? or just drop to zero once the pump stops?
Take it for a ride in the dark, any of the exhaust glow red hot?
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Thanks for the replies. It's stock EFI. Truck seems to run great, starts first turn of key, seems to have good power, no bogging or stutters. Only had it for about a month, and after gave it a tune up it has lots more power, revs up quicker, gas milage still crappy (340km on 72L). But seems to run good and strong. I did pull the spout before checking timing and was 10 degrees before and after tune up. The back fires seem to have lessened In last couple of days, wondering if could be sticking valve?? Think the truck sat for a year without oilchange, before I bought it, and pretty sure I was first to change oil in more than a year, and probably first to tune it up in about five years. Wires stuck to the plug-I had to pull them off with pliers, plugs were rusty and electroid worn to almost nothing.
Thanks again
mat
Thanks again
mat
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Forgot to mention, my brand new exhaust already black after 2 weeks, so I guess it's running rich? Would changing my O2 sensor help that?
Do I have one or two on my 1993 F250, 351 4x4 5spd?
Were abouts is it located, how much work to replace?
Thanks mat
Do I have one or two on my 1993 F250, 351 4x4 5spd?
Were abouts is it located, how much work to replace?
Thanks mat
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