Fuel Cut?

[91eclipse4g63t]

i have a problem with the car i am driving now it is a 91 talon tsi i recently had a few mods done to it by polk performance including a 16g turbo, fmic,550cc injectors, walbro 255 fuel pump, injen j pipe, 2g maf, and 3" turboback exhaust....anyways i got it back after sitting up there for 7 months and it ran fine for about 2 weeks on 10lbs of boost and 2 days ago it started making a popping/backfiring sound out of the exhaust when i try to get on it...i have searched everywhere that i can think of for boost leaks and i have found none..when you drive it like a grandma it seems to run fine but when you try to get in it at all it wont due to the popping/backfiring idk if i could possibly have fuel cut issues or what? please help!!!

and also one of my friends just put a new tranny in his car and now when you hit the clutch all the way in and put it in gear it grinds and when it goes in gear the wheels start spinning slowly(up on jackstands) any ideas? weve bled the clutch and adjusted all that we could(it was working fine before the swap)

 

[sonik619]

I see your profile and I see no safc, data log etc.

What rpm does it start back firing?

Did you use a boost leak tester or just checked that all couplers were tight?

 

[91eclipse4g63t]

i have no tuning equipment yet...it starts this usually about 3-4k it varies from time to time and i didn't use a actual tester for the boost leak i just checked everything to make sure nothing was off...idk what to do...it ran perfectly for those 2 weeks and i did nothing but put gas in it.. i was even pullin on trans ams. but now my car isnt running worth a shit if you need more info let me know

 

[bastarddsm]

Do a real boost leak test, and also pull the plug to se what they look like.

 

[JayRolla]

Man you cant run 550's without fuel control. Even with the 2g maf you are going to run dangerously lean at WOT. Sounds like you also have a boost leak.

 

[Jeff@Slowboy]

Man you cant run 550's without fuel control. Even with the 2g maf you are going to run dangerously lean at WOT. Sounds like you also have a boost leak.

That ECU is telling what it thinks is a set of 450cc to fire X amount of fuel for X amount of air being metered, its really firing a set of 550cc running 10psi on a 16g, how will this cause a lean condition? I agree he needs something to control the injectors, I just don't see how it will go lean.


Oliver
[email protected]

 

[SBR Joe]

Man you cant run 550's without fuel control. Even with the 2g maf you are going to run dangerously lean at WOT. Sounds like you also have a boost leak.

It will not run lean by any means, infact, is probably running very rich. With the added fuel the ECU sees with the injectors, and the added airflow it sees from all the mods and the 2g MAF..its just going ballistic. OP, you need an SAFC controller and a wideband or such to tune with. Your computer is dumping gobs of timing and an extreme amount of fuel in...it is trying to overcompensate for everything at this point. I mean, it is very possible you may have a boost leak (which would just amplify the effects) but tuning is probably issue numero uno. Get an AFC and a wideband, and do a boost leak test just to make sure that isnt adding to your problem.


Joe
SBR

 

[jrohner]

If its popping/backfiring it's not fuel cut. Fuel cut makes a pretty violent jerk -- as in pop flew out of my pop can and all over my console and shifter boot area when I was fuel cutting. At only 10 psi it won't be that bad, but it when you hit fuel cut for the first time you'll know it.

You need to at least have some type of logger to see what's going on. Some people claim the 2g mas matches up half way decent to 550cc injectors without tuning and others say it's way off. You are either way off on fueling or your spark plugs or wires bad.

Until you get a logger and a way to tune, go back to stock injectors and the stock mas.

 

[JayRolla]

It will not run lean by any means, infact, is probably running very rich. With the added fuel the ECU sees with the injectors, and the added airflow it sees from all the mods and the 2g MAF..its just going ballistic. OP, you need an SAFC controller and a wideband or such to tune with. Your computer is dumping gobs of timing and an extreme amount of fuel in...it is trying to overcompensate for everything at this point. I mean, it is very possible you may have a boost leak (which would just amplify the effects) but tuning is probably issue numero uno. Get an AFC and a wideband, and do a boost leak test just to make sure that isnt adding to your problem.


Joe
SBR

It will run lean. Come on, 550's add about 15% fuel. 2gmaf can lean the car out 20-25%. That will cause a lean condition at wot. When I had my 550's and 2g maf I was seeing lots of knock at wot and leaner than 12:1 afr's.

 

[SBR Joe]

It will run lean. Come on, 550's add about 15% fuel. 2gmaf can lean the car out 20-25%. That will cause a lean condition at wot. When I had my 550's and 2g maf I was seeing lots of knock at wot and leaner than 12:1 afr's.

Every car is different...for example...my 1g when i had 550's, 2g maf, 5h 20g, with no tuning....i was flat lining my UEGO...on the rich side. i had a ton of phantom knock from it being wack too. What boost levels were you running? Also keep in mind..the ECU doesnt compensate AT ALL for any of these added levels of fuel/air...but it tries to. I am willing to bet, especially at only 10psi...a lean condition is no where near his problem.


joe
SBR

 

[jrohner]

I don't think AFR is very critical at only 10psi, heck, closed loop is active until around 7psi.

 

[91eclipse4g63t]

i apreciate all of the help guys...i will check into everything and let yall know what happens.. dave@ polk said that he sort of tuned it when he got it running i just dont have a safc im about to install a wideband tho... but if it was my tuning what is wrong wouldn't it have started this problem when i first got the car?

 

[Burtismaximus]

just wondering do you have a fuel pressure regulator. i noticed in your orginal post it didnt say naything about it. but for sure check your spark plugs and make sure you dont have a boost leak. im running kinda the same setup as you except i got a pos afc neo that i have to send in and a datalogger so and a 190 fuel pump. let us know

 

[SBR Joe]

i apreciate all of the help guys...i will check into everything and let yall know what happens.. dave@ polk said that he sort of tuned it when he got it running i just dont have a safc im about to install a wideband tho... but if it was my tuning what is wrong wouldn't it have started this problem when i first got the car?

Yes in theory...thats why myself and a few others suggested a boost leak test just to make sure that is/isnt part of, or the problem.



Joe
SBR

 

[JayRolla]

That is wierd because when I ran my 2g maf I had to add about 10-11% at wot to get good afr and about 8% on the lows to get good fuel trims.

Anyways backfiring, popping is usually from running way to rich. A boost leak poping up will cause the motor to run even richer. It could also be plugs, wires if the spark is breaking up. Have someone watch you in wot and see if you blow a lot of smoke. You should smoke if your running rich enough to cut out.

 

[91eclipse4g63t]

ok...i ran a boost leak test and there was one really tiny leak at the expansion plug in my j pipe that plugs of the recurculation hose to the stoc bov and i got that fixed and i put new spark plugs in it and bam problem fixed.... but there is one other question i have... it has always done this..when you reach about 5 to 5 and a half thousand rpms and hold it there it jerks and kinda pops a bit but when you hold it steady at this rpm and then hit the gas it goes away and boosts on up... and when you hook up the recurc hose it don't do it anymore...??? is it because of the stock bov being a peice of shit or what?...this aint a big deal i was just wondering if that was the culprit

 

[jrohner]

Well if you are not recirculating your BOV and it leaks it will cause you to be rich. You will be rich whenever you let off the throttle and your fuel trim will be off at idle because the ecu will be leaning it out so it's not rich (or trying to).

You need to have your BOV recirculated unless you have a gm airflow sensor AFTER the BOV or are running speed density (map sensor and no airflow sensor).

Also, what you are referring to isn't a j-pipe it's an intake pipe. The j-pipe goes on the outlet of the compressor down toward the intercooler.

 

[JayRolla]

Recirculate the BOV and you will be fine.