loud backfire under hard driving
- Thread starter abber
- Start date
fast97gt
Active Member
Mine does it too, even when the npi engine was there. It still does it with pi engine. I've heard its lack of tune with all the bolt ons. It seems to me it does it worse with the o/r-x.
trinity_gt
10 Year Member
"Backfires" are generally a sign that air/fuel mix is making it unburnt into the exhaust and combusting there instead of in the cylinders. A tune might be a decent place to start but you may also want to verify the injectors and tune are matched, you have no leaking injectors etc.
wmburns
SN Certified Technician
+1 on above.
I have had good luck with fuel injector cleaning/flow matching services such as injectorrx.com. Much cheaper than new injectors. Once done, you have the confidence they are as good as new.
Also, have you adjusted the fuel pressure? If so, this could account for the extra fuel entering the exhaust upon throttle closing.
Also, have you altered the throttle body set screw in an effort to get the RPM to drop faster? This could be a source of extra fuel when the throttle is suddenly closed (ever wonder why the PCM tune keeps the RPM's up and delays the return to slow idle. Well this is it).
I have had good luck with fuel injector cleaning/flow matching services such as injectorrx.com. Much cheaper than new injectors. Once done, you have the confidence they are as good as new.
Also, have you adjusted the fuel pressure? If so, this could account for the extra fuel entering the exhaust upon throttle closing.
Also, have you altered the throttle body set screw in an effort to get the RPM to drop faster? This could be a source of extra fuel when the throttle is suddenly closed (ever wonder why the PCM tune keeps the RPM's up and delays the return to slow idle. Well this is it).
trombonedemon
Well-Known Member
Anybody remember that scene from the movie "Uncle Buck," when he was taking his niece to highschool and his backfire made the entire schoolyard drop to the ground, classic, the old heads might remember John Candy.
One would think you would want to fix that first and foremost, I've heard horror stories of people making parts of there exhaust look like an exploded cigar if enough fuel collects in your Cats.
One would think you would want to fix that first and foremost, I've heard horror stories of people making parts of there exhaust look like an exploded cigar if enough fuel collects in your Cats.
hotdog71
Member
RIP JC!
trinity_gt
10 Year Member
"Hey mister, your car's on fire!" ... "Naw, it's just burning a little oil."
Loved that movie on so many levels. As a kid in the 1970s our family had a 4-dr 1974 Mercury Marquis Brougham that, at times, act very much like Buck's. At one point the shocks were done like his and the rear springs sagged and on the highway when you took your foot off the gas out would come this giant cloud of smoke from the 460's cooked valve seals. A sunken float in the carb led to coughing black smoke on cold starts and a trail of soot down pristine snowy roads in the winter... lmao.
Loved that movie on so many levels. As a kid in the 1970s our family had a 4-dr 1974 Mercury Marquis Brougham that, at times, act very much like Buck's. At one point the shocks were done like his and the rear springs sagged and on the highway when you took your foot off the gas out would come this giant cloud of smoke from the 460's cooked valve seals. A sunken float in the carb led to coughing black smoke on cold starts and a trail of soot down pristine snowy roads in the winter... lmao.
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