back firing at wot, maybe fuel cut?

1sick91tsi · Jun 27, 2004

:thumbdown ok let start, i have a 91 tsi talon awd, and at wot it back fires almost like a fuel cut, very distinct bam bam bam it some times even starts in first at wot arond 4500 and continues through the gears, but if i only give it a little bit of gas and let it rev it goes clean throu to 7200 before the rev limiter. what do u think is wrong open to sugestions here. this is what i have done, 16g, fully proted, exhaust manifold ported to turbo, 2 1/2 dump pipe, apex 2 1/2 down pipe to full 2 1/2 exhaust with a high flow cat, boost controller set at 13 pst, upper intercoller pipes, 2g throttle body elbow, magnecore 8.5 plug wites, ngk bpr7es, dejontol intake pipe, k&n air filter, honey comb removed from maf, amd i think thats it. thanks for the help guys. :thumb:

1sick91tsi · Jun 28, 2004

ok let start, i have a 91 tsi talon awd, and at wot it back fires almost like a fuel cut, very distinct bam bam bam it some times even starts in first at wot arond 4500 and continues through the gears, but if i only give it a little bit of gas and let it rev it goes clean throu to 7200 before the rev limiter. what do u think is wrong open to sugestions here. this is what i have done, 16g, fully proted, exhaust manifold ported to turbo, 2 1/2 dump pipe, apex 2 1/2 down pipe to full 2 1/2 exhaust with a high flow cat, boost controller set at 13 pst, upper intercoller pipes, 2g throttle body elbow, magnecore 8.5 plug wites, ngk bpr7es, dejontol intake pipe, k&n air filter, honey comb removed from maf, amd i think thats it. thanks for the help guys. :thumb:

DSMSpyder99 · Jun 28, 2004

ehh u have no fuel mods of course its fuel cut try turning down the PSI to 10-11 and you should be fine till you get fuel mods. Also since you live in PA i hope your taking advantage of the 93 octane. Also why the hell are u revving to the rev limiter?

1sick91tsi · Jun 28, 2004

actuallu i get 94 octane :thumb:

gotta love texaco. but i was only reving it to the rev limiter to see if it would go to it with out back firing. just a test dont do it other wise. i will try turning the boost down to 11 and see what happpens if it still does it what else could be causeing this, thanks for the help everyone

TSIfreek · Jun 28, 2004

check the gap on your plugs. Set them at .030. Or it could be your plug wires are just old. What may be happening is that when you come onto boost it is blowing out the spark causing a miss fire issue. I only recomend NGK copper plugs with stock heat range 6s for your aplication along with the magnacore or NGK wires. Dont get the irdium plugs because the tips get to hot and the car runs like ass :barf:

with them. I never will run anything but the NGK coppers and are 10 times cheaper.

TSIfreek · Jun 28, 2004

I forgot to add if that doesnt help you may want to get a 2g mass air and a SAFC with 720s. Fuel cut is a possibility. Were the f### is your fuel pump by the way :confused:

psychlow · Jun 28, 2004

Vote #1 for boost leak(s).

A stock 1G can run 15PSI. Fuel cut should not occur until at least 16-17+PSI. You should not be having problems with over-rich conditions or fuel cut.

boosted95 · Jun 28, 2004

check all the vacuum lines

1sick91tsi · Jun 28, 2004

how can i tell if i have any boost leaks. what should i use to test it. and thats what i thought i always read that a stock fuel system can handle like 15 and thats pushing it but i mean im runnin 13 and still hittin fuel cut and its drivin me up a wall when i try to have some fun and next thing u know bam bam bam, no fun. thanks for the help guys.

psychlow · Jun 28, 2004

1sick91tsi said:
how can i tell if i have any boost leaks. what should i use to test it.

VFAQ to the rescue!

4GSixty3 · Jun 28, 2004

Check for boost leakes. Maybe at your rubber couplings on the UICP. Usually, fuel cut is not just bam bam bam, It's BAM and it feels like you hit a brick wall. Your problem is a boost leak.

1sick91tsi · Jun 28, 2004

wow thats cool, ill try it tommaro thanks for the help guy :thumb:

psychlow · Jun 28, 2004

1sick91tsi said:
wow thats cool, ill try it tommaro thanks for the help guy

No problem, make sure you keep this thread updated on what fixes your problem for future searchers.

MattnGsx · Jun 29, 2004

back firing could be a spark issue? Check plugs, wires, coilpack.

-Matt

1fast97gsx · Jun 29, 2004

MattnGsx said:
back firing could be a spark issue? Check plugs, wires, coilpack.

-Matt

if its a coilpack would it throw a check engine light? I have a similar problem ... I'm thinking it's the ecu though.

4GSixty3 · Jun 29, 2004

I dont believe it would set off a CEL. A friend of mine had a bad coil pack (actually 2 friends) and the ecu didn't bring up one. A good way to check if your coilpack is bad is to take off your plug wires at the plug itself and touch all 4 of them against your intake manifold or anything else metal and have a friend turn the car over. If all 4 wires have good spark, then it's not the coil pack.

MattnGsx · Jun 29, 2004

4GSixty3 said:
I dont believe it would set off a CEL. A friend of mine had a bad coil pack (actually 2 friends) and the ecu didn't bring up one. A good way to check if your coilpack is bad is to take off your plug wires at the plug itself and touch all 4 of them against your intake manifold or anything else metal and have a friend turn the car over. If all 4 wires have good spark, then it's not the coil pack.

Hey, don't post crape like this ^. Im not tryn to be a dick, but If I didn't know what I was doing and I tried this, do you know what could happen? You could easily f@ck alot of things up this way; not to mention theres enough electricity in those sparks it could kill you!

Here try this (if its out of range your coilpack is bad):
Also I grabed this from another post and its for a 1g, but I think the range values are the same. You might want to confirm that before you buy a new coilpack, but its basicly just to show you how to do it the right way.

-Matt

MattnGsx · Jun 29, 2004

1fast97gsx said:
if its a coilpack would it throw a check engine light? I have a similar problem ... I'm thinking it's the ecu though.

Only if theres complete failure in the coil pack (no spark).
I had a bad coilpack, and I backfired all the time at about 4800-5100 rpms when I was at wot. If I never got on it, my car was fine. Anyways I tested my coilpack and I was about 2.5 volts out of range on 2 and 3. I swapped coil packs off my old motor, and "WALA" no more back fires. I first replaced plugs and wires but it didn't fix it though.

-Matt

1sick91tsi · Jun 29, 2004

hey thanks for the help guys, the first thing i did actually was checked all the gnition stuff, coils wires and pulgs, everything checked out ok. so i mean from what i have read in other forums and vfaq is it possiable to have a bad ecu, and is there anyway in checking to see if the ecu is bad. hey thanks for the help guys keep it comming. and thanks for the diagram helped a bunch :thumb:

1sick91tsi · Jun 29, 2004

nope not a boost leak. everything checked out ok. im gonna check the coils and wires one more time thou. thanks for the help guys :confused:

psychlow · Jun 29, 2004

Okay. If that checks out, pull your ECU and see how the capacitors look. Might have something to do with that if nothing else.

4GSixty3 · Jun 30, 2004

MattnGsx said:
Hey, don't post crape like this ^. Im not tryn to be a dick, but If I didn't know what I was doing and I tried this, do you know what could happen? You could easily f@ck alot of things up this way; not to mention theres enough electricity in those sparks it could kill you!

Dude wtf are you talking about. Me and my club do this all the time. Very simple to do and if you would kill yourself doing it, get rid of your car . Ok ok so sorry, MAKE SURE THE PLUG WIRES ARE NOT TOUCHING EITHER. Dont go flaming me b/c the way I do things. Very safe way.

1sick91tsi · Jun 30, 2004

finally its fixed

ok so last night i was pissed off and took half my engine bay apart. LOL

. first i started out just cleaning my air filter then i took out all my intercooler piping and took off my throttle body. made sure evrything was clean, then put every thing back together extra tight, well hose clamps and so forth, put it all back in, oh yeah took my boost controller apart and made sure that was all in tune, seemed ok. got it all back to gether and took it for a ride, got on it saw the boost gauge shoot to almost 25 psi, OMG

pulled over, had the lined hooked up wrong to the mbc, stupid mistake well back off i went got on it and no more back firing or anything, :thumb:

. so dont know if it was a combo of things or maybe just a dirty air filter? but i dont care i just know now shes running good. what confused me is that i didnt see and boost leaks when i checked it so what else could it have been :confused:

well thanks for the helps guys :thumb:

1sick91tsi · Jun 30, 2004

finally its fixed ok so last night i was pissed off and took half my engine bay apart. LOL

. first i started out just cleaning my air filter then i took out all my intercooler piping and took off my throttle body. made sure evrything was clean, then put every thing back together extra tight, well hose clamps and so forth, put it all back in, oh yeah took my boost controller apart and made sure that was all in tune, seemed ok. got it all back to gether and took it for a ride, got on it saw the boost gauge shoot to almost 25 psi, pulled over, had the lined hooked up wrong to the mbc, stupid mistake well back off i went got on it and no more back firing or anything, . so dont know if it was a combo of things or maybe just a dirty air filter? but i dont care i just know now shes running good. what confused me is that i didnt see and boost leaks when i checked it so what else could it have been well thanks for the helps guys

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back firing at wot, maybe fuel cut?

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