Wiring Problems Limp mode car turning off etc

[gtrjon]

So i recently picked up a 1991 r32 gtr for cheap. I got it for cheap knowing it had some wiring problems. It has 101km on it and is stock except for a hks boost controller, apexi cat back exhaust, apexi intakes, a torque splitter, and a oil filter relocation kit. So the car pulls good and runs fine about 50% of the time. But randomly the car will bog down and go into limp mode (cant rev out past 2500rpm) if i take it to 2500 rpm it bounces off and the car shakes violently. Than if i turn the car off it will normally be fine but some times it will stay in limp mode when i turn it back on. Also intermitantly after i do a pull in the car when i let off the car's idle will drop and the car will just turn off. Also some times the awd and the anti-lock brake lights come on and stay on. The hicas light also flashes randomly and when the hicas light flashes if the radio is on will restart the song playing (not sure if that matters at all). So the guy i bought it off said that the masf sensors and the masf wiring was done at z tune and he said it fixed the problem for a couple of days but than it came back. Also i put in one new masf and it ran better for a day but than same problem. Also the tps was already replaced. I ordered a new complete wiring harness and just plan on redoing the entire wiring harness. U guys have any other ideas or anybody had a similar experience? i really need some help on this let me know guys

[richard]

yo bro im not sure where to start thats a pretty impressive list you got there. sounds to me if you have multiple systems failing in conjunction would point to a faulty cround on the main engine harness or poyssibly a faulty ecu, however im tempted to say bad ground because the problem is somewhat intermittant. do you notice anything in perticuler that occurs at or just before the problem arises? certain driving conditions, engine rpm, engine temperature (like at opperating temp or not) ect. your from van i believe? im in whistler and i have a copy of the austrailian dealership repair and troubleshoot manual could do some troubleshooting or work through some flow charts. for now i think your bes bet would be to make sure the harness is not rubbed through anywhere, that means starting at the ecu and tracing every wire that goes from it to each respectave sensor or if you have a dvom pull the harness offf the ecu and test for continuity between the terminals and the chassis. eliminate the harness as the problem before moving any further into diagnostics would be your best bet at this point. hope it helps and keep us posted on your progrress and findings.
Cheers!

[TW]

honestly, just redo everything. Will be more expensive, but you will get it done fast.

[gtrjon]

um it is really random. like the oil pressure oil temp and water temp are all standard. I think i am just gonna re do the whole wiring harness i already ordered one. The only thing that happens that is constant is if i do a pull in it like a 3rd gear pull reving out to 7 or so than i let off or push in the clutch and the car will turn off about half of the time when the rpms drop. also it really does not like idling cold.

[skaG]

it's always good to run diagnostic mode on the stock ECU? what sort of boost are you running? I've seen some bnr32 getting into limp mode due to consumption of lower octane gas and high boost which gives knocking. I would also check on ECU wire because most of them had some kind of piggy backs or computers tapped into ECU wiring which makes bad connections, some of them are very poorly installed anyways, hope changing wiring will sort your problems.
good luck

[gtrjon]

yea its a stock ecu. havent ran any diagnostics on it. if the wiring harness doesnt fix it i plan to get a power fc and run some diagnostics. Just running stock boost because of how its running. but i have ran .9 bar before. It has only seen 94 octance since i have had it and it is running rich so low octane is not a problem i dont think. but thanks ill check the ecu wire

[gtrjon]

so i just ran my ecu for codes and got code 55 which means nothing. i ran it for my o2 sensors and one was reading but one wasnt. i really doubt one bad o2 sensor could cause all this crap though wat do you guys think? i checked the ecu wiring and all looks legit none of it is spliced or anything. any more suggestions guys i am at such a loss i dunno where to go next. maybe the ecu is fried?

[skaG]

so you found the problem that one of O2 is not reading, it's time to change it, majority of them are around 100k km so time to maintenance it. fyi, when ecu detect knocking ecu automatically changes map into limp mode and it can be run but less power. how about the other maf sensor that you didn't change?

i would not recommend p-fc, it does not work well with rb26dett ie, when you are high rpm & half throttle rb26 gets boost and p-fc does not compensate fuel map, when it happen fuel ratio gets out of range and driving gets awkward. I would go for HKS F-con or greddy e-manage ultimate with all sensors and you can go for D-jetro system.

[gtrjon]

yea i changed both o2 sensors. still same problems. i am currently pulling my motor for a build. new pistons rods r34 crank big single etc. so hopefully i will figure it out over the winter. and i decided against power fc i am going with link g4 extreme and going with map.

[skaG]

glad to hear you are going for link G4 that looks pretty good to me, how much are they going for?

[gtrjon]

they retail for 2500 for the extreme but i am getting one for 1500. a buddy price brand new.

[skaG]

wow that's a deal for the function of ecu!!