ok, i have a 1j in my sc w/ about 70k mi.... so here is my problem.

Whenever i'm driving (sometimes) when i start moving in 1st gear the car will feel like its studdering, like that feeling of fuel cut at highboost... when the car just jerks but this is at low boost and low rpm also sometimes my RPM drops to about 500 or less. and my voltage drops but then my voltage rises back up. Alternator is fine; when i drive my battery goes up to 13.6+. i thought i was losing fuel or my fpr was malfunctioning, but its set right on.. and the vacuum line to it was fine. also checked all my vaccuum lines and all is good no leaks or cracks. i changed my sparkplugs about a month ago. so now my next thought is my fuel pump, but nothing wrong there, its functioning.. i bought a fuel filter, so im going to try that and hope that fixes it...

PLEASE ANY INPUT WOULD BE HELPFUL!

thanks in advance

--jeriel

 

hmmm, get the walbro 255 fuel pump....check your injectors, when i was doing my single swap, my car would idle weird, die down and then fly right back up, it was my injectors, injector 4 was stuck open, flooding my car with fuel.......check it out

 

You running stock Fuel pump?

 

no, im already running a 255 fuel pump (walbro) is there a way for me to check my injectors without the expensive fuel injector testers?

 

i know this problem...ur fuel pump ecu is bad...bypass the fuel pump ecu and ur problem should go away

 

how do i do that... wanna come over and help me =) im in socal SGV

 

You remove the back seats, remove the driver side panel, and youll see the pump ecu. Then cut the thick wire (yellow I think), and the red????, and splice them together.

Someone help me with the wire colors.

 

I might as well chime in on your thread as our problems may be related. I read something about fuel cut at high boost.

I too have a 1JZ with about the same amount of mileage. There used to be a time when I could boost up to 15psi on stock twins, no problem. As of late, I can only boost to ~12psi. Anything higher results in a stuttering of the engine. It almost sounds like it's coughing. When I dial the boost back, it runs perfectly fine up to about 12psi. I'm running a walbro 255lph with 440CC (may be 550CC) injectors.

Any idea?

Steve

 

is it bad to bypass the fuel pump ecu??

 

Proly mypassing it proly makes your pump run at "max" at all times, not positive tho.

 

Check your plugs....Also check the gap. whats happening is the spark is being blown out either by 1, too high of a gap, or 2, fouling of plugs. just get yourself a set of the cheapie ngk's and youll be boosting back to 15 psi guarenteed.

 

Im not sure Im understanding your symptoms quite clear. This happens @ 500 rpm? Does this happen in any gear? What throttle %? please give more details if you want us to help.

 

ok, let me try and explain a bit more.

Basically the symptoms happen whenever it wants to. Alot of times it happens at low rpm in 1st gear. and about 20% throttle... or sometimes when im cruising on the frwy at about 75 at about 20% throttle or less the car tends to jerk... one time i actually felt the car studder when i went over the little reflectors on the frwy, could this be the ECU? or something major electrical?

 

oh yea i would say change ur plugs, my car used to studder at high rpm and boost and i changed my plugs also my broken coil pack connectors and it was great again.

also btw, is anyone down to help me change out my injectors to my 440s? im thinking maybe the injector is stuck open or sumthing... please. help =) .. free food and drinks

 

What model number NGK and what gap is specified for our JDM 1JZs?

BTW, thanks for the help!