Backfire "not boost leak" Help!

[joeyzaza]

Ok, I have searched everywhere on this site for about 2 months, with no results.

Here is my problem. I get a single backfire, seems like fuel cut, but not too sure, when I am at WOT. This seems to only happen in second gear and up. The car is an automatic. I am currently at stock boost levels, about 11 PSI, with a small creep to 13. I just hooked the stock BCS back up, after thinking it was my MBC.

Here is what I have done so far. Changed the plugs "NGK 6es" gapped at .28. Did that twice. New plug wires, new fuel filter, new battery, and new ground cable. I have fixed every boost leak that the car had on it, and have reset the computer by unhooking the battery a few times.

The car is a 2g 97 GSX. I have a front mount intercooler, with all custom made hard pipes. I have a 1g BOV on it, and aftermarket exhaust turbo back, with no cat. Hardpipe air intake. Aftermarket Boost guage.

My plugs look grayish brown, so I'm not running rich anymore. My BOV is recirculated properly.

I ordered EVO Scan logging software and cable, I should have it here in a few days. My turbo has 0 shaft play "stock t25"

WTF Anyone else have issues like this before, and fixed it???? Please help.

 

[joeyzaza]

Well it used to backfire when shifting from first to second, so on and so on. Tonight it didn't!!!! I fixed the belt yesterday, and never drove it until today. I did a search on alternators, and after sifting through 17 pages, I found one where someone said that if the alternator belt was slipping, the car's ignition may be off.
Also, with a lower voltage I may have been losing voltage to the fuel pump, resulting in less fuel pressure.

This could really be the issue, I want to go WOT from 1st to 4th, but I live in Michigan, and we have 3 feet of snow right now.

Evo scan works great on my car, for logging. Looks really sweet to!!!

 

[joeyzaza]

Still not fixed!

I just drove it. It warmed up and when I drove down the road, where there was no ice, I gunned it, I think it was in 3rd, it down shifted, and pulled like crazy. I layed off it ### I was doing 70 in a 40. Well I dropped off the movie and mashed it out of the parking lot, 1st was fine, then it shifted into second, I kept it at WOT and about 2 seconds into 2nd it backfired, I saw a flash from the exhaust.

Remember its an auto.

I am going to spend the 40 bucks on a fuel pressure tester, and try that.

Any other thoughts would be greatly appreciated. Thanks

 

[joeyzaza]

Its been a blizzard here so I haven't gotten a chance to work on my car lately. Today I did a log, and found my injectors duty cycle is hitting up to 98% at WOT. I have a stock fuel system, on a stock t25, at 13 psi. Car still backfires, any ideas?

 

[Tarantula]

Its been a blizzard here so I haven't gotten a chance to work on my car lately. Today I did a log, and found my injectors duty cycle is hitting up to 98% at WOT. I have a stock fuel system, on a stock t25, at 13 psi. Car still backfires, any ideas?

Your injectors are pretty much open all the time. You need to upgrade in injectors to maybe 550's

Another method is raise fuel pressure and tune the injectors down via safc or link.

 

[joeyzaza]

I shouldn't have to upgrade injectors at stock boost, with a stock turbo, and stock fuel system.

 

[Tarantula]

I shouldn't have to upgrade injectors at stock boost, with a stock turbo, and stock fuel system.

No you shouldn't but you have to because your car is not right at over 80% duty cycle. You either want to fix the car the right way or keep asking the same questions. No one really wants to help someone that does not want to listen.
I'm not going to tell you what you want to hear.

Good luck with your situation.

 

[joeyzaza]

Here is the log.

 

[joeyzaza]

I definatly want to fix it the right way, and I'm definatly listening. I just want to make it right stock, before I go an bolt on a bunch of upgrades. Thanks for all your help

 

[Tarantula]

I definatly want to fix it the right way, and I'm definatly listening. I just want to make it right stock, before I go an bolt on a bunch of upgrades. Thanks for all your help

Are you sure you have the 450cc's Its sounds to me like you may have the 390cc's which were on Autos.

 

[joeyzaza]

my car is an auto, i thought the 390s were on 1st gen autos, mine is a second gen. I'm about to do a fuel pressure test, i just picked one up from autozone.

 

[dylan702110988]

Are you sure you have the 450cc's Its sounds to me like you may have the 390cc's which were on Autos.

Only the 1gs had the 390cc injectors, all the 2gs came with 450cc injectors.

Im having the same problem in the upper rpm range around 5-5.5k, but im on a evo3 16g (auto too ).

Please let me know if u get this fixed!

 

[joeyzaza]

will do!

 

[1_2befast]

I don't know what you can log with Evo scan, but I would check out your MAF signal/readings. I high MAF reading would be causing your high IDCs. My thoughts are you either have a boost leak or you have a bad MAF. It never hurts to do another BLT on these cars even if you just did one when this thread was started. Good Luck.

 

[joeyzaza]

For sure, I was thinking of doing another boost leak test. I was also thinking about if the issue is from the maf, being that I seem to be running rich. Something is telling my car to push the injectors so far.

What should the maf readings be roughly? I have a logger but not sure what to look at on it for this problem.

I'll try to do some research on what the MAF flow should be at.

EVO Scan lets me log lots of stuff, its super fast too!


Thanks

 

[joeyzaza]

Ok I think I have attached a log. Its in word format. I have the air flow, timing, duty cycle and RPM on it. See if anything looks wrong, I'm still new to logging. Thanks

 

[joeyzaza]

Well the car began smoking oil "blue smoke" at idle. I figured valve seals, but I did a compresion test and I got 160 through 150. I was impressed 150xxx miles on the car. So I did another boost leak test and had a bubbling sound comming from the oil. I then checked the T25 for shaft play, and its has some serious side to side, and feels like some minor in and out... Its blown! I checked the LICP pipe and there was some oil residue in there. I must have blown the oil seal. Could a failing turbo be causing this backfire?

I un hooked the stock BCS and hooked the waste gate up directly, the car still backfires when shifting.

I have a 14b sitting on my tool box, I'm thinking I'm going to install that in a few weeks, plus some 550s and a 190. I have a SAFC that I will hook up too. I just wanted the car to be right before I put bolt ons on.

 

[joeyzaza]

Well I found another boost leak. Its the throttle body shaft seals. They leak super bad!! I just ordered new seals, throttle body seals, and a biss screw from MachV. Once they are here I'm putting them in. I will update then about the backfire.

The blue smoke went away after I changed the PVC valve, and got rid of the breather on the valve cover, I ran it back into the intake.

Hopefully this will fix the issues, so I can put on the 14b without worries. Thanks

 

[joeyzaza]

14b is on, still waiting on shaft seals, I guess there was an issue with my credit card and MachV?? Anyways I will have it running on Tuesday. My 2g oil return line got all jacked up, so I ordered one from Forced performance. Update soon.

 

[joeyzaza]

I replaced the shaft seals, and finally got to drive it after the turbo install. Its night an day on how smooth it runs, even out of boost. Shaft seals were the problem without a doubt!! Logs look way better.

The title of this thread should be; backfire, probably a boost leak. Because it was.

Now I just need to fix my why my turbo boosts to 17 psi, when hooked up with no boost controller. Well off to reading, thanks all!!!


Resolved!!