backfire

[97_4g63t]

To start i've changed wires, checked coil packs, fixed boost leaks and changed plugs to bpr7es gapped to a .028. The car will back fire if i try to turn the boost up past about 15psi. My af ratio is also only in the 13.1 to 13.5 range at peak boost (22psi is what i'm trying to run.). It seems to run good in first and second but in 3rd and up it back fires, i'm guessing because its under a load not just spinning. I dunno what else to try Or check, i've had this problem for like 3 years now. i've probably read a thousand tech articles trying to figure it out. Any ideas Or help would be much appreciated. thanks

 

[DSMxJB]

Possibly fuel cut.

 

[Boostinsideways]

Boost leaks. Something is making your car run way to damn rich underboost, and when you let off to shift your getting backfire.

 

[97_4g63t]

I done a boost leak test and i have very little leaks. 26 pounds on the regulator and 26 on my boost gauge. i have a very small leak from my idle air screw i believe that's what it is but i'm not sure how to even fix that. It back fires pretty hard but i wasn't thinking that it was fuel cut because at a partial throttle it does it but not near as bad. It just feels like it stumbles. i was told i throw a flame and when i boost it smokes really bad.

 

[simple jake]

What kind of fuel are you running? 13.5 is super lean even with E85. Have you changed your fuel filter? Maybe its restricting your fuel flow causing fuel cut and your lean condition.

 

[compression]

If a 2g fuel cut is similar to a 1g, mine didnt backfire at all, the car just stopped like it hit a brick wall.
i would say its running to rich, but 13.5:1 is just way to lean.

My car is doing the almost identical thing, even getting about 13.5:1 in 3rd, but only 12:1 in first and second. but my problem is the sump on my fuel tank is lower then my fuel pump and i believe under acceleration the pump cant quite pick up the fuel fast enough.

But a backfire usually comes from a rich condition or some sort of ignition malfunction.

 

[97_4g63t]

i'm only running 91 octane and i have changed my fuel filter a few times. That's what i didn't get its back firing and its still running lean.? Sorry about the other threads i'm on my phone and had bad service. bov is recirculating and i've put a new maf on.

 

[tonyspyder]

couple things you might want to look at. check for any loose hose. mines would do that when the hose to the turbo popped out . check all hoses i mean all the little hose going every where. bigger injectors? i have a e316g and i got 650 to cover the boost. what tunning device do you have? i think these guys can help you a little bit better if you can show the data logged. One thing that happens alot too is the fuel injectors wires are pinch. This will cause your car to run lean. check those wires. last thing to fix the problem is run some race gas. 100 octane should help you out alot. if you want to turn up the boost some more go 110 or e85. hope this helps

 

[97_4g63t]

thanks i'll check those and try some higher octane. i have an apexi neo just didn't wanna lean it out even more. its not even on. i have 660s and i just turned my fuel pressure down to 20. it was doing this on my last motor before all the mods. i have a few more really small vacuum leaks i'm gonna fix and see what happens. i don't have a logger but my wide band will log i'm pretty sure, i'll have to try and find something to hook up to it.

thanks i'll check those and try some higher octane. i have an apexi neo just didn't wanna lean it out even more. its not even on. i have 660s and i just turned my fuel pressure down to 20. it was doing this on my last motor before all the mods. i have a few more really small vacuum leaks i'm gonna fix and see what happens. i don't have a logger but my wide band will log i'm pretty sure, i'll have to try and find something to hook up to it. thanks for all the help guys i've done everything on this car and had no idea what the Hell i was doing ha ha i'm learnin slowly.

 

[skatershawn]

Wow... I think you should turn you base fuel pressure back up to 42psi and use the neo to tune for the 660 injectors!
I wouldn't fog with you engine like that! I can only guess that your running lean because you fuel pressure is extremely low!

And YES you can still backfire in lean conditions it just not as common as backfiring due to rich conditions!

Read this Info:
*Exhaust system backfires occur in engines that have an emission system malfunction, like an air injection system diverter valve problem, an exhaust leak, or when the catalytic converter has been removed. In some high-performance vehicles, when a driver shifts up and lets off the accelerator, the engine has a moment of running rich. This causes an incomplete burn which causes the fumes to explode in the exhaust system along with an audible clacking sound. However this condition is a result of working smog equipment, and is unlikely to cause any damage.

A fuel injected engine may backfire if an intake leak is present (causing the engine to run lean), or a fuel injection component such as an air-flow sensor is defective.

Common causes of backfires are:

Poor or unregulated engine timing is often a cause of intake backfires, but can also be responsible for exhaust backfires
Improper wiring in the ignition can also lead to timing issues and backfires
Low fuel pressure, clogged fuel filters, and weak fuel pumps could cause a severe lean air-to-fuel ratio during fuel injection
Missing or damaged catalytic converter can result in backfires out the tailpipe*

I would go over all these to insure these couldn't be causing the backfire!
FIRST I would turn the fuel pressure up and tune CORRECTLY, and if that doesn't solve it, I would work my way down the list!
Second, I would fix your vacuum/boost leaks as this is a huge cause of lean or rich condition, potentially causing backfires.