redtop SR misfire/fuel cut under load after 3k-4k rpm

[SR2oD3T]

i have my redtop running very smooth and fine for years. always stock boost with basic bolt-ons. walbo, apexi intake, stock T25, HKS bov, greddy FMIC, tomei exhaust manifold, turbo elbow and 3inch exhaust. was running stock 0.6bar of boost. smooth all the way.

THE PROBLEM:
after i turn up the boost with my greddy pro fec A to 0.9 bar, it starts to misfire/fuel cut on 3-4k rpm. first gear is fine, second gear will start to boost weird. feels like choking under boost. it still have power to go up to red line, but it just misfiring or something. 3rd gear the same, didnt try on 4th and 5th. i try to turn down the boost to 0.8 bar, still the same. however, i turn to 0.7 bar, it doesnt choke. it runs smooth like 0.6 bar. i felt that only under hard boost/under load.

QUESTION:
i've searched and will check on my spark plug gap, then check on boost leak. is there any other suggestions or any other owner have the same problem? any other ways to check on? i just wanna solve this problem be4 i but my gt2871r in. i will kep this update if i have find the problem. thanks guys.

KELvin

[Team DET]

i had the same problem as you my spark plugs where loose made my car misfire like crazy and it choked too only when i went wot hope this helps

[SR2oD3T]

yea i have a feeling on the spark too. cus if its boost leak, i will have choke on lower boost too. i'll go check on the spark plugs in one or two days. thanks for the input.
KELvin

[tt99ol]

might be a boost leak from your bov
if its a push type (not ssqv or synchronic)
it might be blowing open at that level of boost
quick fix is to tighten the spring via the bolt on top
wow my sentences are like a crazy staircase of ideas

[cotbu]

I've dealt with this type of problem before and it's always the injectors, except when i was maxing out the mafs.

It can be a number of things, knocking, tps, mafs voltage, yada yada sex...
it could also be your setup,
if you have the 370's and your turbo is in good shape, i'd say injectors.
check the voltage on your mafs while this is happening, also tps
stock intake pipe?
start with a basic tune-up, checking plug gap, vacuum hoses and piping, fuel filter, inspect coolant and oil, check ecu for codes yada yada yada octane and sex

[steve shadows]

Make sure your ignitior coil pack is properly grounded to the head and the firewall

[SR2oD3T]

i just pull out the spark plugs and checked. they are all in good shape. when i install them back, i made sure they are all ground good. i went for a spin and still have the same problem. it feels like a boost spike. i felt the turbo trying to kick in during 2-3k rpm, then in 3-4k rpm, there no power, then all of a sudden, the turbo kicks back in strongly. i might have to check on boost leak later on and also need to re install my boost control.
i wanted to upload some pictures for the spark plugs but photobucket is down. i'll keep it update till i solve the problem.
KELvin

[SR2oD3T]

ok, i have done tighten up my HKS SSQV. i thought i solve the problem at the begining. first, i start of 0.9 bar of boost. i boost it at 2nd gear, it still have boost cut, but 3rd gear and boost at 0.9 bar all the way without any boost/fuel cut. 4th the same. so i thought i just tight it up more will be fine. however, i kept driving it and tried to boost it. it just wont boost up above 0.5 bar even i set my electronic boost control to 0.9 bar in every gear. so, it stays at stock boost after the engine gets hot. i went home, tighten the SSQV more till the bolt hits the BOV, same thing. stock boost after engine gets hot.
so now, plugs are good
bov tighten all the way
i m gonna check all the pipping from my FMIC, tighten them up and see.
will it be my stock AFM? i hope not.
really wanna get it fixed be4 my gt2871r is on.

KELvin

[downshift_sideways]

1. Read Ecu Codes. (if found a code, be sure to reset the ecu properly)
2. Check coilpacks and ignitor and make sure ground is snug.
3. pull spark plugs and check if they are flooded..and gapped correctly.
4. Check TPS voltage .45 - .50
5. Check Mafs if your running a z32. Check your grounding unit. Make sure it is grounded good.
6. Check for any sign(s) of boost leaks.
7. Check your injectors make sure they are pulsing correctly.
8. Check IACV between runners (3+4)

I'm betting it's TPS tho.

[Howard92884]

Do you have an adjustable FPR with your walbro? I had a problem like that before. Installed mine and worked fine after.

[golfer17]

I just had a similar problem this weekend. It was cutting out and sputtering after 10psi, but the afr's were leaning out slightly instead of going rich, so I knew it had to be spark. Checked my ground for my coilpacks first and found that it had loosened up a little since I swapped injectors this weekend (have to pull the upper intake mani for s14 sr's), but after I tightened it, same problem. So next, I checked all the wiring, maf, grounds, tightness of spark plugs, etc. and still same thing. Luckily though, since I have two complete motor swaps, I swapped out all my coilpacks and found that fixed the problem. so once you've checked everything I and others have mentioned, and still haven't fixed the problem, it's probably a bad coilpack or wiring to the coilpack.

Btw, anyone know for sure If a faulty ground would short out or cause a coilpack to fail? I'm wondering if that did it or it just wore out from Oklahoma heat and lots of abuse over the last few years.

[SR2oD3T]

i will do a final check on the boost leak. tighten all the pipping. my plugs are pretty new and looks good. and all coils are ground good. if i still cant fix this, i'll just borrow my friend's redtop and start swapping parts like tps, coils, ignitor, cas and all the shit.
update: now it wont even go past 0.5 bar when the engine is cold. no cut at all, but its not fun at all when u cant turn the boost up.

KELvin