Misfiring/Backfiring when taking off in lower gears

Say I take off in 2nd or 3rd from a roll. I get lots of sputtering and often a huge backfire. The whole car bogs down.

I can do the same 4th or 5th on a highway and there is no problem.

After the misfire or backfire, the engine soaks for 20 seconds as if it has been soaked in fuel even if I am trying to drive it normal. Fuel cut has been disabled in my tune. The tune is the same that it has always been. Nothing has changed.

I can run 2g timing or 1g timing. I can run it rich or lean...doesn't matter.

I recently changed the fuel filter, spark plugs, and wires with NGK/NGK Blues.

What on earth is going on? Compression is perfect across the board. This happens with full exhaust or with the downpipe open. /ubbthreads/images/graemlins/dunno.gif

 

Oh no...come on guys don't make me go to tuners for this. /ubbthreads/images/graemlins/frown.gif

 

[James]

It's been less than a day.
It's a holiday weekend
And it's not the easiest question to answer. It could be many different things.

 

Not a holiday weekend for everyone. /ubbthreads/images/graemlins/smile.gif

Surely someone here has some idea. Close plug gaps to .018 maybe?

 

[prove_it]

If everything was fine then bam! now there is an issue. I would suspect plugs are bad first. More info on your car would help. It's like the guys that go to the parts store and say hey I need that part on my car that spins. I don't what kinda of car it is, but tell me what I need.

 

[transparentdsm]

plugs, filter, fuel sock, injectors, fpr. i had a similar problem and it was a clogged fuel filter. every time i laid the throttle down it would sputter and backfire. i put a fuel gauge off the rail and ran it out on the hood to get a reading while putting a load on it and when i put the peddle to the floor i watched my fuel pressure almost go to 0, it was scary.

 

Thanks everyone, all of my mods are clearly listed in my signature, all you really needed to do was "click".

I closed the gap of my BPR7ES from .028 down to .020 and that didn't help.

The coil secondary is slightly out of spec. 1.2 ohms on the primary and 15.5k on the 2/3 secondary. Expensive as heck to take a chance on something like that!

Wondering if is fuel related somehow like Transparentdsm mentioned. Warlboro 190lph in fuel tank with new sock, new fuel filter...hmmmm maybe the FPR is bad.

 

So you ran a few feet of fuel line outside the hood from in between the fuel pressure regulator and rail? Wasn't that sort of a long pain in the ass run? Did you just tape it to the windshield?

Thanks

Quoting transparentdsm:
plugs, filter, fuel sock, injectors, fpr. i had a similar problem and it was a clogged fuel filter. every time i laid the throttle down it would sputter and backfire. i put a fuel gauge off the rail and ran it out on the hood to get a reading while putting a load on it and when i put the peddle to the floor i watched my fuel pressure almost go to 0, it was scary.

 

Seems to be in the tune somewhere. Leaned out to 10.8:1 in all loads above 1.88:1 and no more misfire.

 

Still misfiring...at my wits end! Flirting with the for sale section soon. /ubbthreads/images/graemlins/mad.gif

 

[ktmrider]

Quoting blkchr91:
Seems to be in the tune somewhere. Leaned out to 10.8:1 in all loads above 1.88:1 and no more misfire.

10.8:1 is rich, not lean.

Or do you mean your O2 pegs at 10:1 then "leans out" to 10.8:1?

 

It is leaner than other ratios though and want to preserve my engine as long as possible during troubleshooting. I know these engines just well enough to say that I'd better get this fixed soon or I will have other problems to fix. It is set at 11.1:1 now though and the problem persists.

 

Read your edit...no it is set to 11:1 now and generally stays there at WOT.

 

I'd like to post a csv file in here of my latest log. Is there a way to do it?

 

Here is a print screen of the log....17-26 knock counts at around 6k rpm!