turbo boost leak? figure change my topic werd...

[chevy2303]

I, new to this forum. I just recently rebuilt my brothers 300zx. 1mm oversized pistons,t-28 turbos,chipped ecu,750cc jecs. i've got the car running and oil presure up.
The car fires up immediately, it has rough idle with boost at -20vac, if i accelerate any it starts to miss out more and run rougher then if i turn the key off it goes to perfect idle for 4 seconds then shuts off. im confused so any ideas would help.

Thx

[Ace2cool]

Pull codes from the ECU. Diagnostics are in the tech articles.

http://www.nicoclub.com/nissan-technical-articles#300zx

[chevy2303]

i pulled codes on ecu got code 55 no problems, tried to do 02 sensors but the engine light never came on, also the light on ecu when back in mode one doesnt turn off with key, thinking this might be batt drain problem or part of run on problem.
i tested the injectors 4 at 10 ohms, and 2 at 11 ohms.
pulled the plugs all of them were wet and a lil black.
we cranked the moter over with plugs out, all the cyclinders were injecting, kinda looked like might be little too much fuel possibly making it sound flooded while running.
When its running key on sounding flooded the boost reads around 14 vac and when key off car runs smooth its 20 vac at idle.
i still have stock FPR. on it would that be making it dump in too much fuel? im going to make gauge and check the fuel pressure real quick to.

thanks.

[KornFlakeZ]

Since you changed the injectors, checked for pinched o-rings. Those suckers cause the cylinder to become flooded with fuel and might explain why you have wet spark plugs.

[chevy2303]

Hi, been lil bit since my long ago post. we solved the continued run on problem and bad idle with another idle hose to passenger side for idle control valve. all the at that point i hadnt had car warmed up all the way and full water circulation throwing off the temp sensor/causing poss fast idle richness. so now car runs smooth at idle, and more responsive. and plugs had white tips(changed to bosch irridiums from ngk, but now got ngk iridiums to possibly try).
i got conzult working on it(came with car i was lil clueless for sec) left o2 seemed dead so we replaced it. and it fluctuates faster then the right side(old one). so gonna change that right one out and also put in the wideband on adjacent pipe.
so now the car drives fine while not boosting, then if you boost it starts popping/cutting out a 0psi, then after shift the car stalls which is most likely due to blow off valves on maf system, and we got code 14 vehicle speed sensor?
also checked fuel pressure and it bout 38 idle and if you rev it the psi jumps to 50 and the back to 38.
(timing light 15 degrees btc, new tps set .45 and goes to 3.96 same as the old one werd)
boost leak test pending: found one positive boost leak on a bov conn, and some on low presure side but still seems to drop relly slowly from 2psi to one over like 15 sec. when i tried to pust 5 psi in system i hit my bro with the cottage cheese cup we stuffed in on side .
so any more possibilities on stalling or the cutting out when trying to boost would be apreciated.
thanks.

[chevy2303]

didnt check injectors for leak but did power drop test on conzult when we found left side o2 bad, drop reading seemed looked similar to conzult book. we hadd like 250,350,255,375,260,400, thinking think some obtuse reading coming from bad o2 bank.

[Ace2cool]

Soudns like you're tracking it down well.

Yes, those readings will be from your bad O2 bank. The car senses the bad O2 flow, and defaults to a very rich map, which is what you were seeing.

Not sure about the VSS code, but dI don't think that'll cause your problem. Fuel pressure sounds good, TPS, good.

Your problems are definitely vacuum related. Boost leak test is a must.

[chevy2303]

hi, we found 2 positive presure boost leaks near intercooler, and we took pre cat off passenger side to changed out other o2 sensor and put in wide band to, but with air pressure at 4-5psi. air is leaking past the exhaust propeller. they're supposed to be new reman t-28 . i didnt know if they were spooling they might thrust back lil to stop the leak or what.
werd are they supposed to do this gonna suck to have to take motor back out...
thx.

[chevy2303]

we fixed all the boost leaks we could find. I believe with car running oil pressure up no boost can go back through the turbos. we took the car out today with wideband o2 hooked up it idles at 14-15 afr, normal driving 13-16 afr, but if i go to boost when i get to 0 psi static presure it goes excessively rich 8.5-9. it pegs at 8.5 and wants to start popping at +3 psi boost. The fuel presure gauge i hooked up read 36 idle but if you rev motor or put under load to boost i just instantly jumps to 56-60 before its even pasts 0 psi of boost. im stumped thinks its FPR or dampener...

[Ace2cool]

Are you just revving it in neutral? Cause that won't tell you anything. Gotta be driving with load on the engine for accurate readings.