Odd Stuttering S13 Blacktop

[GLoBaLReBeL420]

Quick: Car will run fine for around 30 min and then all of a sudden starts misfiring/stalling at idle and when pushing the car. Here's the issues i pretty much notice . .
Quick note....
Vacuum at idle = -18 to -20 (depending on what the idle is at)
Boost holds all the way to redline when car isn't misfireing
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Info:
94 Blacktop
Nistune Daughterboard
740 Nismo injectors
Z32 MAF
Nismo FPR
Walbro 255
GT2871 64 AR
HKS Wastegate actuator
Apex-i ACV-R
WideBand gauge and sensor
NGK BKR7E @ .032
NEW coil packs
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Issue:
Car starts up fine
Drive around for 30 minutes and get to operating temp
Car will begin to start reading lean on the Wideband
Car will begin to misfire/stall and read VERY LEAN (15 -17:1)
As car stalls I have to give it WOT to keep it running and during this time, it sounds like cylinders are misfiring (almost like a WRX engine)
Once car completely stalls, I am unable to start car again (must wait like an hour before starting it again. Even then, it barely runs and is misfiring like crazy)

What I've done:
Coil Packs: Replaced
Spark Plugs: Replaced (even gapped smaller to .028)
Walbro 255: Replaced
Fuel Filters: Replaced
Z32 MAF: Cleaned and checked connections
Coolant Temp Sensor: Replaced and checked resistance. all within spec.

What I've checked:
Z32MAF - Possibly Dead?
- Igniton on Voltage: 0.42
- Idle Voltage: 1.1 - 1.2
- My Link for instructions (http://forums.240sxone.com/showthread.php?t=26778)
TPS- Seems OK
- Closed: 0.52
- WOT: 4.2
- ECU correctly shows 'throttle closed' flag when throttle closed
- FSM states 0.4 CLOSED - ~4.0 WOT
FPR- Could be bad
- Found instructions for testing FPR without a gauge. (http://www.drifting.com/forums/showpost.php?p=77848&postcount=2) Thoughts?
Fuel Pump
- Fuel pump is working and has full 12V (direct line to battery with inline fuse)
Ignitor Chip: I do not know how to test this. I looked it up and the directions didn't match with my chip. My chip shows "22020-50F00" for part number. On one side it shows E1,E2,E3,E4 and on the other side it shows (I1,I2,G,I3,I4).
FPR: I thought this could be it, and will be purchasing a fuel pressure gauge soon to run inline before the fuel rail to see if I'm losing pressure for some reason.

So...
Ignitor Chip: It could be that the ignitor chip is getting to hot (operating temp) and failing at that point. This would explain why I can drive it in the morning without problems, but after about 30 minutes it starts having the misfires and stutters and then just dies.

MAF: The readings seem low for the MAF. I could also see this being the problem as more air is getting through than the MAF is reading which is causing the lean condition I see on my wideband.

Fuel Pressure: Clogs in the fuel filters/flow could be causing the starvation and thus misfires and stumbling. I already replaced all filters and pumps, but the problem still stands.

Any help at this point is greatly appreciated, as I've basically gone as far as I can think of. I have Nissan Data Scan I and used it for logging the ECU while driving to capture if any sensors were going crazy. This looks to be unhelpful at this point. I have the logs if anyone would like to look at them.

[jedi03]

fuel pump wiring or o2 sensor?

[rawgarage]

Check grounds and FPR

[GLoBaLReBeL420]

Fuel pump wiring is direct to fuel pump from battery with inline fuse.

O2 sensor, I believe, isn't used as I have the NisTUNE daughterboard and tune. (I am not 100% on this, and did replace the O2 sensor a while ago. I notice on the Nissan Data Scan software that the O2 reads 0 - 3 while the car is running.)

I have checked all major grounds and made sure no corrosion.
- Checked ground at battery
- Checked ground at intake pendulum

FPR will be checked tonight using the method linked above (looks to be a legit method)

[GLoBaLReBeL420]

Checked Fuel pump wiring for voltage and full 12V is being received

Connected and disconnected O2 with no difference in behavior

Checked ground at MAF and no problems.

Didn't check FPR, and will check this tonight. Anyone know how to test the Ignitor Chip?

[jedi03]

https://www.youtube.com/watch?v=6IDF1w_P10Y

[GLoBaLReBeL420]

https://www.youtube.com/watch?v=6IDF1w_P10Y

Thank you sir. It looks like the info in the vid matches the info in the link I posted for the instructions I grabbed. My ignitor chip actually has a G in the middle instead of an E, but the process looks to be the same.

Will test out when car is warm, and then again after car start misfiring and stuttering.

[GLoBaLReBeL420]

**Update**
Took the fuel filters out again and the filter directly off the gas tank to the sump was filled with black crap again. Decided to pull all the filters and replace. Replaced filters and car ran much better. [I may have to drop the tank and get it cleaned if this keeps happening]

Then, put the fuel pressure gauge on the fuel feed line after filter before rail and found it was at 27 psi at idle (~865rpm). So, I think the FPR is bad or just got clogged. I'm going to pull the FPR tonight and see if it is clogged. Hopefully after cleaning it will return to 35 psi.

Will update with info.

[jedi03]

definitely clean if theres junk like that! will mess up your lines fast too!

[GLoBaLReBeL420]

I went ahead and drained out all the gas from the tank. Bought 10 filters and am going to slowly change them out over the next few months. Dropping the tank and cleaning is a pretty expensive ordeal. So, this will hopefully allow me to clean it out (albeit slowly) via filters.

I pulled the FPR and there really is no way to clean it. So, I'm keeping an eye on it for the next few weeks to make sure that the PSI after a filter change stays the same after each change. This will tell me that the FPR is good and keeping a stable PSI.

[jedi03]

i would recommend keep an extra fuel pump too...

[EnnEssEnnKAT]

Not sure if this helps, I had an issue the other day where my car was driving fine one minute then wouldn't go over 50% throttle without stuttering and almost like half power. Turned out to be the vac hoses under the throttle body, I have them plugged but a plug ripped and I had a vac leak. Repairing it solved my problem. Good luck

[GLoBaLReBeL420]

@jedi03 : Yep. I actually still have my original Walbro 255 that I replaced with a new Walbro. Since the fuel pump wasn't the issue, I kept it in case I need it again.

Going for a 40 miles drive this weekend, and will push the car hard along the way to see if the issues remain.

[GLoBaLReBeL420]

@Enn : Thanks for the help/info. I've got a boost gauge that shows perfect vac under idle ~20 - 21 ng so it shouldn't have anything to do with Vacuum. But I'll double check.

One thing I did notice is people stating that the vac for the FPR should be directly off the TB nipple and have no other T's off of it. This guarantees that you have a good VAC for the FPR to regulate PSI. I currently have it T'd off for my boost sensor for my ACV-R.

[GLoBaLReBeL420]

Just wanted to continue the thread for people that cared (500+ views), found that someone felt the need to pour something into my gas tank for no reason. I've had to completely drop the tank and clean it out; followed by replacing all filters and lines again. Will probably have to replace the filters again in a few weeks just to be safe.

Going to run a fuel system cleaner through too just as a safety net.

TL:DR = Get a fuel pressure gauge to help troubleshoot issues. :-)