fuel cut I have no idea whats wrong. help

[DSM_PWR]

I've been having this SAME exact problem for two months now and STILL cant figure it out..

Ive dont boost leak tests, Changed/gapped plugs to .26-.28, converted 2gmas to MAFT setup, swapped out BOVs, and still keep getting the "hit the brick wall" feeling...

My car seems not to do it by boost, but by RPM range..
in 1st i can go all the way to 6k rpm
2nd i can go to 5k rpm @ 19psi
3rd i can hit 4500rpm at 14psi

When i do feel fuel cut the boost just drops down about 3-5psi... increases and fuel cuts again...

A/F ratios are 10:9-11:5 across the RPMs..

[v8s_are_slow]

Originally Posted by DSM_PWR

I've been having this SAME exact problem for two months now and STILL cant figure it out..

Ive dont boost leak tests, Changed/gapped plugs to .26-.28, converted 2gmas to MAFT setup, swapped out BOVs, and still keep getting the "hit the brick wall" feeling...

My car seems not to do it by boost, but by RPM range..
in 1st i can go all the way to 6k rpm
2nd i can go to 5k rpm @ 19psi
3rd i can hit 4500rpm at 14psi

When i do feel fuel cut the boost just drops down about 3-5psi... increases and fuel cuts again...

A/F ratios are 10:9-11:5 across the RPMs..

For starters, not sure what you guys are using for boost control but try going ahead and taking your boost controller off the car. Run the line from the boost source, straight to the wastegate. Do that and see if it helps any. Heck, I had to do it myself yesterday to keep my car from sputtering (think I was running too much boost and was blowing out my spark I guess). I'll be putting it back on sometime later.

As for the GM maft, do you have any lights blinking on it? DSM_PWR, is your afr's getting leaner as you get to higher rpm's?

[DSM_PWR]

No blinking lights, stays green throughout cruise and red on WOT. It does get leaner throughout the RPM so i add fuel with the SAFC, im still a little new with the MAFT so i leave WOT knob zero out.

[Merkles]

Let me know if you figure it out. This is driving me crazy and I'm getting tired of spending money on parts I don't need.

[v8s_are_slow]

Are either of you monitoring your fuel trims, knock, and timing?

[DSM_PWR]

I use a mixture of e85 so at 11:1 i doubt im getting knock. But either way my timing stays pretty constant... I dont get tooo far into a log because i cant reach redline

Im thinking it has to do with my fuel pump/filter maybe? or definetly a spark issue. Tommorrow i will buy new plugs and wires, any way to check coilpacks?

[v8s_are_slow]

I'm not very familiar with using E85 so I wouldn't wanna give any misinformation on that. But wondering about your fuel trims, wondering what your plugs look like, and wondering about any boost leaks. If you're running blowthru, it's a lil harder to get a leak and then get kicking out of it, unless maybe it's after the maf. If you're running a drawthru, boost leaks suck a big one.

Have you tried either taking out the boost controller (whatever it is that you're using) and running the vacuum line straight to the wastegate? Or if you don't have a boost controller, disconnect the vacuum lines and go straight to the wastegate. If you're on an internal gate, it should only put you at around 8 psi and will make it hard to sputter. That'd be a start if you can get it to stop sputtering. Guessing both of you guys have aftermarket bov's as well correct? Cause the stock plastic ones suck.

Doubt it's pump or fuel filter.

[DSM_PWR]

My fuel trims are pretty close to 0 about +/- 5%.

Whatever the problem is, i belive its growing because i was able to run 24psi just fine before anything. Once i felt it sputter i was stuck at 19psi just fine. now i can only run up to 14psi and even then "sometimes' it still sputters....

[v8s_are_slow]

Well did the sputter just come out of nowhere? What's the fuel pressure at? What are the maft settings at? Which version?

[Merkles]

I've been doing some reading, it is possible that the O2 Sensor going bad (but hasn't triggered a CEL) has caused a super rich condition? Maybe spark blowout? Or perhaps maybe the knock sensor is bad or picking up phantom knock and pulling timing? I'm not sure the knock sensor would cause the sputter but I think the O2 sensor might be a possibility. What do you think?

[v8s_are_slow]

Well, what's your plug gap set at? You'd usually blow out the spark if the gap is too wide, or insufficient spark at the spark plug to be able to ignite the fuel. You did say you're running NGK's right? BPR7's? 6's? Gap should be at 0.28.

As for the O2 sensor, yes, it could make it run a lil rich if it goes bad but I dunno that it'd make it so rich that it sputters but can't rule anything out. This is one of the reasons a logger comes in handy cause most will give you engine codes, or you can see what the motor is doing. This prevents you from having to experiment by dumping tons of money into your car to see if it fixes the problem or not. By the time you end up fixing the problem, you can easily spend more than the cost it'd take to get a datalogger. Plus, being given limited information, it makes it hard for anyone on here to track down the problem other than to just tell you, "try this....try that".

[Merkles]

That is very true, although I should get a logger I was trying to save for DSMlink and get that instead. I'm heading back up to NY for July 4th weekend, I have a bunch of extra parts kickin around up there, Im going to bring them back and swap out things 1 at a time to see if any of them fix my issue.

[v8s_are_slow]

Well, good luck with it.

[2gGSXEclipse]

I use to hit fuel cut at 14 psi, after i got my SAFCII havnt had the problem since

[DSM_PWR]

Im getting really frustrated w/ this

Changed the plugs/wires, hoping it would be an ignition problem and nothing. i have a logger and doesnt seems to show anything wrong. but then of course i could be looking at the wrong things..

I think im just gunna drop it off at a shop ### im done

[v8s_are_slow]

What are the fuel trims looking like, what are the numbers on the timing, and are you getting any knock? What rpms are you at for each of those as well? Boost level? The exact plugs you're using, the exact gap, and your exact current mod list. Also, what are you using to log with? Any check engine lights?

[Merkles]

Evo 3 Longblock (Black top CAS); Spark plug wires are correctly in coil and injector wires are switched at ECU
Greddy 18g Turbo @ 15psi
Evo III Exhaust Manifold,
VooDoo III MBC,
1G BOV,
Prothane Motor Mounts,
SS Auto FMIC
3" Catback,
Evo 8 Fuel Pump,
NGK BRP6ES Plugs @ .028
Bosch Ultra-Premium Wires

The only code I have for the check engine light is Random Misfire

but like DSM PWR said the car accelerates (feels sluggish doesn't pull as hard as it should) then sputters for a second around 4500-5500 rpm then continues to redline.

[DSM_PWR]

oh man...

*My fuel trims are pretty close to 0 about +/- 5%.

*Timing is pretty steady, seems to be making its way to 19-22 deg by redline but is usually stopped by fuel cut somewhere around 5k-6k

*As far as i can tell no knock, im only using an OBDII logger so i cant exactly see knock on my 2g OBDII

*Last night i held 20psi till about 5k rpm then fuel cut

*Im using NGK BPR7ES gapped to .28

*My Mods are in my profile but ok...
PTE 5031e 50Trim
FIC 650cc
MAF-T 3' GM MAF Blowthrough Setup
TiAL BOV
FP Exhaust Manifold
SSAC FMIC
3’ Exhaust
o2 Dumptube Housing
MBC
Aeromotive AFPR
Rewired Walbro 255lph
AEM Wideband
ARP Headstuds

*No check engine lights

[v8s_are_slow]

Forgot to ask but have both of you guys checked your base timing?

[DSM_PWR]

How do you check? someone told me it might have skipped a tooth

[v8s_are_slow]

http://www.vfaq.com/mods/wayback/Bra...ne/timing.html