Severe stuttering around 3k or 12psi!!!!

[gsxcellent]

Ok so it says im a newbie but ive been workin on my dsms for some time now, so tough question in a newbie section...

My car has the listed mods minus the SAFC...(not installed and tuned yet) The entire car will run fine until about 3k rpm or 12psi and then it will stumble and backfire horribly until i let off the gas or if the rpms and boost is lowered. At first i thought fuel cut, knowing my mods so far, but i knoq/have heard that fuel cut is like tying ## car to a tree and runnin out of chain. I have boost leak tested, 20 psi held fine for a good time before starting to lower very slowly. I have disconnected my MBC and reconnected the stock BCS. Nothing seems to help. Plugs and wires are both new and not cheapo. Injector resistence was tested fine.

(550cc injectors and SAFC are being put on as a shot-in-the dark to fix the problem tomorrow so they are not a part of the problem)

Anyone have some input on this, its driving me crazy!

 

[FastGS-T]

Do another boost leak test, this time spray soapy water everywhere and look for bubbles. EVERYWHERE. Any check engine lights? Is your egr hose off? Ive experienced serious fuel cut and light fuel cut. So you might still be experiencing fuel cut. Never underestimate the power of a boost leak!

 

[gsxcellent]

Thanks i will get on that soapy boost leak test in the morning its 1:15am im tired and my birthday is tomorrow .

A good present would be a good running AWD DSM .

 

[bujang_hensem]

check your fuel pump, well it work for me as last option. After installing the AFPR, the meter show that my fuel presure not enough when under load. now change to walbro 255 it rock again

 

[dub2gsx]

When was the last time you changed the fuel filter? If it's been over 10,000 miles or you can't remember, change it! I had simular problems and that was it. My car felt like a new car after I changed it! Also try to see if your plugs are gapped correctly, makes a big difference.
Are you venting your bov or recirculating? If venting then check into recirculating.

 

[gsxcellent]

It has been well over 10,000 miles without a fuel filter change, i will get on that but wouldnt that create a problem that gets worse over time, or could it just happen all of a sudden like this. I feel like the problem has occured because of some combination of mods i have done. Yes i am recirculating

 

[ddavisaf]

What kind of spark plugs are you running?

 

[Ultimatedsm]

1. Bad plugs and wires
2. Boost leak
3. Coil pack/Transistor
4. Bad MAF
5. Leaky caps on those 1g ECU's

Check these one by one and I know you will find the problem. Trust me its one of these. I had a similar problem as you and it turned out to be a bad MAF, the pain in the ass part was that the car drove fine but once boost hit, the car would hit a brick wall. I checked all those parts I listed (I checked the MAF last and didn't check the 2g ECU). So I was like what the hell is going on, I hold 20 psi for 30 seconds, my plugs are fine and gapped correctly, wires are brand new, coil-pack and transistor was swapped (Friend had spares) and I was just like what the &%*#(&$*)@#&$*)#(@&$*(# is going on. Then it turned out to be the MAF, stupid thing. Anyway sorry to bore you with my MAF story, just check out everything thoroughly or I have to hurt you.....just kidding. Good luck with the car and again I know its one of these for sure.

 

[gsxcellent]

What kind of spark plugs are you running?

I was running with bosch platinums because my NGK's were changed out but i recently changed the plugs to A/C Delco, didnt fix problem.

1. Bad plugs and wires
2. Boost leak
3. Coil pack/Transistor
4. Bad MAF
5. Leaky caps on those 1g ECU's

Thanks UltimateDSM #3 and #4 are the only two i havent checked so far so hopefully that will be the key! (is there any way of testing the two parts to make sure they are working or do i just have to buy a new one?

 

[desertspyder]

I had the exact same problem and I tried everything but nothing worked until I checked my plug gap. The plugs were densos and were supposed to already be gapped but they were all over .040. I gapped them all to .028 and it completely fixed the problem. The plugs must have been kind of "blowing out" at higher psi.

 

[Boost Demon]

I had the same problem after my fuel pump install, turned out that I didn't put the seal back onto the top of the fuel tank opening the right way and had to take my time and do it over . I had almost the same symtoms too, my car also wouldn't go over 10psi of boost at right about 3,000rpms until I fixed the problem.

 

[gsxcellent]

OK heres a crazy thing (could possibly be temperary). I removed the plugs and checked the gap to .028...everything was good and so i also installed my 550cc injectors cuz i figured its worth a try. Now my SAFC is not installed yet and i know i should not run the car on 550's without it but i put it all together and took it for a spin. All stuttering has dissapeared...I even mashed the gas and it flowed smoothely through all gears. Im afraid this is only temperary?!? The SAFC goes on today, maybe i just had a leaky injector?

 

[andymoraitis]

If that's the case then maybe you had a flow issue with your stock injectors that was causing the motor to stutter/miss at high RPM's. Add the AFC, get it in tune and see what you have, but in light of what you're saying, the issue may have been fuel delivery.

Keep us posted,

Andy

 

[PSI NRG]

I had this kind of problem, I found out that the welds on the end tanks of my front mount intercooler weren't done well and it was leaking through there 1200 intercooler too!! You think it would be quality

 

[gsxcellent]

Thanks a lot guys, i will post my results after the SAFC is installed and tuned properly.

 

[gsxcellent]

Long sad story short....my Apexi S-AFC was supossed to come in the mail the day i posted this thread but UPS has lost the package ...it got about 25 minutes from my house before being lost in transaction!....The investigation is being done now but i did get it insured so i guess all is well.

 

[eclipsegsx1736]

Switch to NGK BPR6ES or BPR7ES and gap them. It's what we all use. Bosch platinums just don't work for us, along with most other plugs out there.

 

[Booster-Shot]

Long sad story short....my Apexi S-AFC was supossed to come in the mail the day i posted this thread but UPS has lost the package ...it got about 25 minutes from my house before being lost in transaction!....The investigation is being done now but i did get it insured so i guess all is well.

I beat up the ups guy and stole it.

 

[gsxcellent]

Hahaha you must have stolen someone else's ### i just got a confirmation that they found my SAFC, and it will be shipped to me ASAP. thanks a lot guys, im sure ill have some tuning questions sometime soon (once im back from college)