Random pop or backfire

PorterzSupra

PorterzSupra

New Member
Oct 25, 2005
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Hebron CT
I am running 3 inch exhaust from turbo into muffler, everythigs fine but im gettin a random pop or light backfire what causes that? Id say it happens about every 7 minutes of driving. My friend has a WRX and it does it too, more frequent and its a bigger, louder pop. I dont understand how it can run good then suddenly pop. Anyone know what causes it?
 
N

NDBoost

Guest
no cats or running rich more then likely.

I can rev up my engine, go from 2k to 3k back down to 2k and up to 3k repeatedly and shoot flames.


Supras also tend to backfire a bit if you go into boost lightly and let off the gas continously.
 
N

NDBoost

Guest
mine does the samething, itll lightly pop at random times. But when i get into boost and let off repeatedly it makes a nice big pop. Do you have cats?
 
M

mixmastermatt

Former Nissan Junkie
Mar 30, 2006
124
0
0
Taftville, CT
You have a wideband O2 sensor? If not, swing by and we can use mine to see if you're running rich under low load situations. That is what causes the popping, especially when you have no cats.
 
S

Satan

Supramania Contributor
Mar 31, 2005
1,594
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36
Tampa
I get 'em while just idling. Exhaust is 3" with a hi-flow cat....

A friend had a similar issue with his N/A and it turned out to be a leak at the gasket for the EGR... we changed it out and no more pops while in idle. I am going to check mine out, when I go to install the FFIM I have. Maybe that'll do the trick for me...
 
ians13

ians13

New Member
Nov 8, 2005
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Jacksonville, fl
PorterzSupra said:
I am running 3 inch exhaust from turbo into muffler, everythigs fine but im gettin a random pop or light backfire what causes that? Id say it happens about every 7 minutes of driving. My friend has a WRX and it does it too, more frequent and its a bigger, louder pop. I dont understand how it can run good then suddenly pop. Anyone know what causes it?
Click to expand...

small amounts of fuel in your exhaust combust from heat and hot exhaust pipe.
 
staticpat

staticpat

Supra Chair!
Mar 30, 2005
450
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Birmingham, AL
I get that too, I dynoed to check it out. The tuner assured me it was normal especially for inline 6s. The only time it gave me problems was when my idle was really low the pops would try and stall the car out. Also I have no cat if that could be part of the cause.
 
I

IJ.

Grumpy Old Man
Mar 30, 2005
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I come from a land down under
Joel: I don't think so as the only time it will do this is on closed throttle when there is enough vaccum in the exhaust to pull air in past the flange and you get back on the gas. (closed throttle the ECU goes into decel cut so no fuel)

cliff notes NFI ;)
 
jetjock

jetjock

creepy-ass cracka
Jul 11, 2005
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Redacted per Title 18 USC Section 798
Joel, any leak upstream of the lambda sensor will shift the loop rich. Any leak downstream won't effect it but it'll sure goof up a gas analyzer. You may not fail emissions but it'll give the analyzer a whacky lambda.

Afterfire (backfire is an induction event) on decel is usually caused by (as IJ said) leaks in the exhaust system, causing atmospheric O2 to combust with unburned fuel. Adding to this can be large diameter exhaust tubing or excessive fuel on decel caused by an improperly adjusted TPS or dashpot, among other things. Didn't you just adjust your TPS Porter? ;)
 
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