Power problem under load: fuel cut??

panger

New Member
Nov 22, 2005
7
0
0
Burnaby
Hi all,
I have a 1990 LHD supra with a 1JZ swap (of course!). Since i got the swap done everything was good at first, but then after many months of driving it a problem started to develop. It happened less frequently before but now does it everytime i even come close to flooring it.

The problem is that when i give it any decent amount of gas and the boost comes up, the power falls off DRAMATICALLY and it makes a flat blat sound (almost like its farting). It almost feels like a couple cylinders go dead but not quite. It is pretty much always at least 2500 RPM before it will happen. Also, if i have done work to the car with the battery disconnected for some time (days), it wont happen for the first day of driving.

Has this happened to anyone else or know what it could be? The shop i got the swap done at has no clue. Its all nissan mechanics there. My first guess is a fuel or boost cut of some sort but i have a Mine's modified ECU that is supposed to have any of those limiters removed. I tried swapping in a borrowed ECU (stock) but the problem persisted. It is not the fuel filter or fuel pump as those have been swapped (2 times with the fuel pump, first stock, then walbro, then a skyline GT-R pump). I have a HKS intake and just a cat-back 3.5" exhaust. I have a profec boost controller as well but it is never turned on. no point.

If you can, PLEASE help as i have parked the car for now since it is no fun to drive and bought a 240sx. Its no Toyota but it is fun.

PS: pretty sure its not the coil packs as i have dealt with that problem before.
 

SupraClaou

Supramania Contributor
Sep 1, 2006
846
4
18
Athens,Greece
Check the ignitor or try one from another 1jz car...
I think Mines ecu doesn't eliminate the fuel cut :nono:
Mines just rises the fuel cut to another level (say 18 psi)....
Your exhaust (3.5') can flow up to 1000 rwhp :sarcasm:,and I think
there is your issue.You have a very BIG exhaust for the stock twins.
Factory boost (stock 11-12 psi) is limited by the factory exhaust,with
small diameter,cat,pre-cat etc., exactly like my jdm 2jzgte on my mk3.

And switch that boost controller ON ! Set it at 13 psi of boost and write
down what happened...
Other choise is to install flow restrictors to your very free flow 3.5' exhaust .
 

Freshmaker

New Member
Feb 3, 2007
396
0
0
Oconomowoc, Wi
When I first did my 1JZ swap my Map wiring was going bad. It reacted just like your talking about, but didn't throw a code.

I *think* it was the brown wire from the ECU to the sensor.
 

The Reaper

Single, and lovin' it!!
Jan 10, 2006
1,909
0
0
Florida
anyway you can get a video of what its doing???its hard to read another persons writing of what its doing with the different sound fx lol
 

panger

New Member
Nov 22, 2005
7
0
0
Burnaby
thats good to know freshmaker, but after the last time it happened i checked and no code :( but thats a good idea reaper. i think i may do that when i get back home at the end of the month. i'm also gonna make up a boost leak detector that i saw instructions for. feel stupid for not doing that a long time ago.
 

Freshmaker

New Member
Feb 3, 2007
396
0
0
Oconomowoc, Wi
panger;959700 said:
thats good to know freshmaker, but after the last time it happened i checked and no code :( but thats a good idea reaper. i think i may do that when i get back home at the end of the month. i'm also gonna make up a boost leak detector that i saw instructions for. feel stupid for not doing that a long time ago.

Like I said, mine didn't throw a code either.