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backfire under acceleration

Old 12-09-09, 12:05 PM
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backfire under acceleration

what can cause WOT accel backfire .. in all gears ( neutral included ) .. not boost level dependent .. rpm ~ 6.5K ... A/F ( innovate LC-1 digital ) dont go under 10.5 .. over 14.... ... egts normal

i floor it .. it revs..boost..pulls great .. gets to 6.5k .. backfires under WOT .. hesitates a split second .. and continues to rev ( i lose a bit of boost ) but will continue to rev ... sometimes back fires 2wice

i have had this problem for a while now and everything seems fine

new plugs ( 9`s )
wires
rewired ignition coils to igniter ( new power and signal wires )
upgraded fuel pump , rewired straight from batt
relocated + rewired knock sensor to rear housing
injectors cleaned + flow tested
stock ecu ,
idles great .. starts cold warm whenever .. never floods ..
upgraded inter cooler intake exhaust ...
only CEl i have is for the speed sensor .. i cut the wire going to the ecu so i can go over 180 km/h ..

hypothetically speaking .. backfire is unburnt fuel .. or excessive fuel ... unburnt ... but should this not show up on my a/f as an ... <10

any ideas , suggestion would be much appreciated
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Old 12-09-09, 12:07 PM
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bad primary coil.
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Old 12-09-09, 12:09 PM
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Have you messed with the ignition set up at all lately? I left off a connector on the coil packs while putting everything back together a few years ago and it had similar reasults as you. Maybe plug wires are bad, or loose?

What boost levels are you running? Why did you cut the speed sensor wire?
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Old 12-09-09, 12:11 PM
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i have tried .. 3 leading coils .. and i have the same result ... and nothing is unplugged or loose

boost is 10 psi ... it`s not boost cut im experiencing ..because i get the same wot backfire in neutral ... if i rev to redline... it`s just rpm dependent .. not boost / load
so weird
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Old 12-09-09, 12:13 PM
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bad MAP sensor or connector not plugged in?
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Old 12-09-09, 12:19 PM
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Maybe check the grounds out. Even in neutral does it hit the hesitation right at 6.5k just like under load?
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Old 12-09-09, 12:22 PM
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map connected ... grounds are clean + then some
same hesitation in neutral .. as under load ... it`s ONLY RPM dependent .. ~6.2-.3-.4-.5 K

i dont have another MAP to ..try..but for example i can rev in all gears under full boost up to 6k and no problem ... it pulls really hard .. good A/F and EGT ... boost 10psi

it just does not like going over 6K
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Old 12-09-09, 12:31 PM
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It might just be ignition break up, but it really doesnt seem like it running only 10psi. Why are you running 9's with that low of boost? Have you tried going to back to 7's and 9's?
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Old 12-10-09, 07:04 AM
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Do you have an A/F guage? It could be too rich for whatever reason. Any readings below 10 and my car breaks up bad.
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Old 12-10-09, 10:57 AM
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i do and it never goes under 10.5
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Old 12-10-09, 11:51 AM
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What ECU? What is your fuel setup?
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Old 12-10-09, 03:56 PM
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stock ECU .. stock injectors ... cleaned / flow tested
walbor 255 rewired to battery with relay ....
plug`s all 9`s ...
ignition coils rewired .. new signal wires from ignitor .. new power wires ( did this to try to cure this break up )
relocated + rewired knock sensor to rear housing
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Old 12-10-09, 08:25 PM
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Have you replaced the coil pack harness? I know you rewired the coils to the ignitor, but there's a harness that goes from the coil pack to the connector behind the power steering pump stock. It's about a 1-foot harness, has all the plugs for the coil packs. If the harness has a ground wire, it's the old style coil pack harness - the new updated part doesn't have that ground wire.

I've seen a similar problem that was a bad coil pack harness.

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Old 12-10-09, 08:52 PM
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that harness no longer exists on my car .. when i rewired the signal wires from coils to igniter .. and from batery to coils ... that harness became obsolete ....
i did the rewiring job because i suspected a possible problem with the ignition harness
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Old 12-10-09, 08:59 PM
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Did you have the old style harness? How much of it did you use?

Also, the factory harness has some shielding to prevent interference. If it's picking up some sort of RF interference and isn't well shielded that could cause problems.

Big dumb one too, make sure you don't have something funny going on like the trailing and leading coil signals swapped or trailing one and two signals swapped. With that many wires it's easy to confuse them in your mind. The proper signals need to go to the right coilpacks.

As well, make sure the plug wires are on right - again, simple stuff, but this is the time to double-check and make sure everything's on there right. Swapped leading and trailing will make the car run VERY weird, for example.

Dale
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Old 12-10-09, 09:42 PM
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dale i appreciate it but if i had some crossed wires my car would not drive normally to 6k rpm ..
and i used shielded wires for the coil signal wires which are rewired from the ignitor plastic connector all the way to the colored coil plastic connector .. similar with power wires as well

the problem is the same as before rewiring


it`s simply an rpm dependent WOT backfire ... aroun 6.5 k ... very very loud

i will try to post a vid .. but it`s hardnow cuz my car is stored and snow outside .. cant really drive it around
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Old 12-30-18, 03:16 PM
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If all connections where Checked if it was me I would check the fuel filter
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