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I'm running a Jzx81 motor, x90 ecu, z30 harness, single turbo and stock injectors ...car idles fine, revs up when its parked, but as soon as I drive it and it starts to make boost (any) it leans out like crazy. It doesn't seem to matter what rpm I'm at as I can drive it around without getting into boost, but it leans the second I go from vaccum to boost. We've swapped out the MAP sensor twice and it hasn't made a difference.

 

Ecu?

Injectors?

Wiring related?

 

Any ideas??

 

 

Brinkin.

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Gotta be something fuel pressure related. Are you running an adjustable FPR? You should throw a gauge on it and see what it's doing when you go from vacuum to boost. If you can single that out, maybe fuel pump is dying.

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1) pinch off the fuel return line from the rail. if the motor bogs out badly from the excess fuel you have bad injectors. if youre going lean this is probably not the case.

 

2) crack open the ecu and see if you have a chipped board.

 

3) send mark your wiring and a few bucks. itll be sorted out in no time.

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If you open the ECU, see if any of the capacitors look like they are bulging at the end. A friend (Electrical Engineer) at my last job kept having weird intermittent problems with his 3000GT VR4. He opened up the ECU and found capacitors were bulging out ready to pop. A few dollars and some solder later, cured all his problems.

 

Might be worth looking at.

 

close-up.jpg

 

Bulging_capacitors.jpg

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Sounds like fuel pump wiring , you can ground pin 4 of the circuit opening relay and do a 12v mod (bypass the resistor) or wire your fuel pump directly to +B , to rule out fuel pump wiring issues associated with the jzx90/jzz30 fuel pump ecu . The jzx81/jza70 use a circuit opening relay and fuel pump relay witch the ecu controls by grounding pin 4 of the circuit opening relay via the fc pin of the ecu allowing power to flow to the fuel pump through fuel pump relay witch controls voltage by grounding pin 3 of the fuel pump relay via the fpr pin of the ecu to allow power to flow through the fuel pump resister dropping the voltage to the pump . The jzx90/jzz30 uses a fuel pump ecu witch controls pump voltage via fpc pin of the ecu by varying a 0-5v signal to the fpr pin of the fuel pump ecu thereby controlling voltage output to the pump .

Good luck !

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sounds like your car is going into limp mode. check your engine codes. I had the same problem it was o2 sensor wiring problem.

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when my capacitors were done, car would initially die out occationally while driving... then eventually got harder to start to the point where it would only stumble and die.

 

could be the ecu but mine died literally in a day so i never had anything hooked up to it to diagnose the problem. i had spark and fuel, so i took my ecu to a friend and voila. done capacitors

 

but i'm leaning more towards a fuel problem in this case

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So when I posted this last night I forgot a few things.

 

First off, this is in my s13 running a painless

stock ecu and injectors

in tank walbro wired into the painless

ecu relayed to switch

injectors and coils wired into another switch

SARD fpr with AN lines supply and return

single turbo gated at 7psi

jzz30 harness has been untouched other then being wired into the relay/ switch panel.

Continuity from all sensors, injector, and coils. Good ground, alternator charges good.

the car falls on it's face anything over 0 psi.

 

 

we're gonna check the ecu and fuel pump to see if either are bad. thanks guys

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do you run a fuel pressure gauge? sometimes it's the dumbest thing. on a friend's car which kept leaning out under boost, we found that the car just wasn't flowing enough (even with good fuel pressure at idle or low boost). under more boost it went crazy lean.

 

at first we thought not enough fuel, but he had twin or triple walbro or some other bs so it had enough juice... new injectors, and new fuel pump, all receiving full voltage. it just wasn't moving enough fuel from the tank to the feed the injectors

 

turned out to be a dirty fuel filter.... lol. threw that shit on the dyno and it had more than enough fuel to deliver 500+whp on a 2J running stock twins

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What do you use as a signal to drive the fuel pump relay , if you are using the jzx90/jzz30 ecu pin it will not work because it signals 0v at idle and ramps up to 5v for full pressure and will not drive a 12v relay . Also I am working on a 1jz-gte s13 right now and I know the jzx90/jzz30 ecu will not drive the fuel pump relay so I don't use the ecu to drive the fuel pump relay , what I did was ground the black and pink wire of the s13 fuel pump relay and the pump will run when the ignition is on .

Good luck

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Did this car ever run right ?

nope.

 

do you run a fuel pressure gauge? sometimes it's the dumbest thing. on a friend's car which kept leaning out under boost, we found that the car just wasn't flowing enough (even with good fuel pressure at idle or low boost). under more boost it went crazy lean.

 

at first we thought not enough fuel, but he had twin or triple walbro or some other bs so it had enough juice... new injectors, and new fuel pump, all receiving full voltage. it just wasn't moving enough fuel from the tank to the feed the injectors

 

turned out to be a dirty fuel filter.... lol. threw that shit on the dyno and it had more than enough fuel to deliver 500+whp on a 2J running stock twins

We weren't running a fuel filter. Maybe my fuel pump is dying.

 

What do you use as a signal to drive the fuel pump relay , if you are using the jzx90/jzz30 ecu pin it will not work because it signals 0v at idle and ramps up to 5v for full pressure and will not drive a 12v relay . Also I am working on a 1jz-gte s13 right now and I know the jzx90/jzz30 ecu will not drive the fuel pump relay so I don't use the ecu to drive the fuel pump relay , what I did was ground the black and pink wire of the s13 fuel pump relay and the pump will run when the ignition is on .

Good luck

 

The fuel pump is on a switch/relay on the painless.

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so to follow up on this thread (because i found it in a google search just now), his issue was a shitty harness. if you put pressure on it all the injectors starting working again. so i ziptied it to his strut tower and the car ran fine under boost.

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