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Discussion Starter · #1 · (Edited)
Hey again, I've gotten together my 2JZ swap after my 7M spun a bearing. I'm using a 2JZ-GTE VVTi from an Aristo with stock ECU and R154. The harness I'm using is from Tweak'd Performance. No other mods besides a full 3" exhaust and intercooler kit. Stock fuel pump running at 12v. Running NGK BKR7E Gapped at 0.030 (also tried 0.032 and 0.028 with no difference)

The issue I'm having is the engine goes super lean and sputters/bucks/bogs/stutters/misfires you name it under boost. Typically followed with some backfiring from the exhaust. I have an AEM wideband that reads 14.5-15 AFR at idle and cruising at a set speed. As soon as I try going WOT, the AFR briefly goes to 13, maybe 12 AFR before shooting up to 16-19 AFR which I immediately left of the gas and the AFRs return to 14-15 at crusing speed. I have seen the boost gauge hit around 13 max which may be related to boost cut, although no CEL codes related to over boosting. However the lean AFR along with all the issues above happen under almost any boost. It never sustains a rich AFR under boost and Ive never seen it run at 11 AFR.

If i steadily accelerate with no boost the issue appears to not be present. However there tends to be times were even slight acceleration seems to cause issues, typically after prolonged driving. Higher RPMs also tend to make the issue worse.

At this point I'm afraid of driving as I dont want to hurt the engine. The Map sensor reads 2.56v with engine off which is pretty much correct for atmosphere. TPS, Accelerator pedal and throttle motor resistance all check out. I checked for vacuum leaks by pressurizing the system. I did find one damaged hose, didnt fix the problem. Coils look completely fine, cant find a crack on them. I suspect maybe the fuel pressure regulator but I have no direct way to test that. I'm lost on what to do at this point. The only CEL codes I have gotten are 82 (from missing aristo body computer) and 42 because I'm using a R154 instead of automatic with the ECU.

 

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Discussion Starter · #2 · (Edited)
Leaving an update in case anyone else stumbles across this problem. I figured my issue was fuel as the engine was getting air and spark for combustion. After checking the MAF, MAP, O2 sensor etc. if figuredthe engine was starving from fuel under load. So I looked at my gas tank. My gas tank was dirty from sitting for 10 years before I bought it off the previous owner. I removed the gas tank and removed the fuel pump. I saw the fuel sock was clogged with rust and other containments.

I emptied the remaining gas and removed the fuel level sender as well. I then prepped the tank for cleaning. The entire tank was in bad shape so I filled it up with vinegar and let it sit for a week. After letting it sit in vinegar, I drained it and used a high pressure hose to knock any of the remaining containments in the tank. This worked really well and the tank came out pretty clean. I flushed the tank a couple times and ran my old gas through it a couples times as well. I cleaned up the gas tank neck, fuel level sender and fuel pump bracket while I was at it.

I then replaced the Delphi pump with a Walbro 255 along with new fuel sock and hose/clamps. Replaced fuel filter and then reinstalled everything. After that I filled it up with some gas and took it for a spin. Goes all the way to redline full boost with no issues. WoT is running between high 10s to low 11s in AFR. AFR is also running richer under acceleration instead of going lean.

So there you have it, a dirty gas tank and a clogged fuel pump was the culprit. It was my mistake of not cleaning out the fuel tank when I replaced the Delphi fuel pump over a year ago when I still had the 7M.

Hope this help someone.
 

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Glad you fixed it 👍
 
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