Help me plz zilvia i am running out of ideas

[street_white180sx]

Aight my car has been breakin up under load. Check codes got a CAS code and MAF code. My alternator went bad the same time so i got that fixed. Replaced the CAS and the MAF retimed the motor to 15btdc. No more codes are present. My car still is stumbling as i go under load and pass vacuum into boost. as soon as the needle hits zero it happens and then starts to buck and stumble. I checked maf voltage and its sendin out the right signal. it isnt fuel because i run my car on AV gas now. Mods are FMIC Mines ecu and boost up to 15 psi. I also pulled the plugs and they look fine and the gap looks fine. Any help wud be appreciated guys thanks.

[Nizzan4u2nv]

Check your TPS and swap in a good stock ecu.

[cotbu]

19 views 1 reply hmmmmmmmmmmmmmmmmm
Ok, get as close to stock as possible, Recirc that bov somehow, then see what happens. you may have boost leaks or exhuast leaks both can cause the stumble you described.

Question, same problem with the stock ecu?

As you hit equall pressure you bov piston might fluctuate causing the slight stumble, so the unmetered air ecsaping, doubles the effect.

Try adding more washers to the BOV if running atmospheric.

[S14DB]

You check that you aligned the CAS properly?

[McRussellPants]

thats gigantor boost leak, my car did that exact same crap when the oil cap I was using for a recirc plug went MIA.

[street_white180sx]

Thanks guys for your help i will put my stock ecu back and try that because these conditions went down hill soon as i put this peice of garbage in btw the mines is a waste of time the mild tune is trash the car felt no better actually my times dropped in the 1/8 from a 8.9 to a 9.1 . i will double check these things and check back with yawl peace. The sad thing is i am a auto tech and this is cuttin my ass.

[S14DB]

Are you 100% that it's a Mines ECU? There are a lot of knockoff tunes out there.

[street_white180sx]

i am having a feelin that my fuel pump is dieing on me again damn walbros car has a fuel problem definately. plugs are a lil white i doubt its the av gas causing it. i gotta verify it by checkin my fuel pressure but i wont access to one of them until monday.

[S14DB]

You're running 100LL in your SR?

[street_white180sx]

yes i am. y? i run it mixed wit pump

[S14DB]

LL stands for Low Lead.

[street_white180sx]

i know it does this is y i mix it alot of the guys do it over here. either that or they run c16 i kno its not good for the o2 sensor but its good for the motor and keeps egt's down considerably

[S14DB]

It's not good for the whole system. Valves, Rings, Plugs, Fuel pump, Injectors and FPR can all be damaged by Lead contamination.

[street_white180sx]

thats a 1st i never heard bout it affecting all of those things. if anyting i hear it cleans all of the carbon out your motor. hence leaded gas. and cleans your valves.

[street_white180sx]

i pulled my return line and no fuel was present at all with the car running. i tried another one to verify so i am quite sure the pump is done. some of your input wud be appreciated.

[S14DB]

FPR stuck closed?

[shayrgob240]

what is AV gas? Aviation gas by any chance? lol

[cotbu]

Fuel Lines could be swapped, every take them off? check it anyway.

The fuel returns to the tank, through the stock FPR. It being stuck close would give you higher fuel rail pressure. Works just like a the stock bypass valve or BOV, meaning air is a fluid. Boost keeps it shut, Vac open it.

[rim_bender]

what is AV gas? Aviation gas by any chance? lol

Yup, thats it

me and a buddy always go fill up a couple 55gal drums of it at the local airport, it works good

and whoever said lead is bad, they are absolutly wrong, its only bad for o2 sensors and cats, if you got no cats and dont mind chanign o2 sensors a litle more oftne it can only help


and to helop this guy out, the white on your plugs is from the lead in the gas more than likely, it turn your exhaustg tips white too dont it?

[S14DB]

Wait? AV gas isn't bad, yet it coats the spark plugs?

[Chrischeezer]

hate to highjack but... im having the same problem, BUT only after i drive around for about 10 min..feels like a misfire, my Air fuel ratio goes to lean during the brake-up... all my plugs are white...

i changed alot a sensors (and 4 MAF's.. but still havent changed the o2... or the ECU...

can a O2 make a car run lean like that?

[street_white180sx]

i am quite sure i didnt cross route the lines i already switched out the fpr. my car is falling flat and breakin up like it is starving so i am guessin pump. for the plugs with them being white i kno the leaded gas burns off white but one of my boys says it shud have a reddish color on the plug if the mixture is right. i am completely stumped man i am almost to the point of sellin this car. The funny thing is that i am trained tech to a ford dealership. I ain new to this kind of stuff.

[Chrischeezer]

dont feel so bad... i work at nissan, and i still can't figure this one out.. lol

[GSXRJJordan]

My immediate guess is a boost leak - that makes you run rich though... but the car runs most of the time out of the boost, so you cant expect a boost leak to present symptoms of running rich (like fouled plugs). Your ECU, MAF or your O2 sensor could be causing you to run lean, and would have nothing to do with your fuel pressure, although if you pulled the return line off the fuel rail and saw nothing while the car was on, something is definitely wrong (my walbro SPEWS fuel down the return line at idle).

Sounds like you're on the right track - just switch stuff back to stock (or known good parts) one part at a time, and DONT GIVE UP! Once you fix this problem you'll forget you ever had it :)

[street_white180sx]

lol sr's jus tough at times i guess. oh yea the nissan dealership is next door from the ford dealership and under the same owner so i get discounted prices on nissan parts gotta love it man. btw i finally sorted out my problem. it was the fuel pump damn walbro gave out on me. i had a spare ford pump popped it in and problem is gone. so i gotta order another walbro this week :hahano: thanks for your help guys.

[street_white180sx]

guys i still have this problem and i just bought my walbro. and after a while it now dumps fuel. i am so lost i am bout to sell this lemon of mines. the car breaks up and falls flat when flooring it. but if u lightly gas it will clear up. at idle my maf is puttin out about 1.7 volts. is this right come guys plz i gotta get this car running. i havent boosted in 2 weeks :(
Things i have done.
1.Pulled fuel rail crank over car fuel injectors are pulsing also check with a stephescope while running to check none of the injectors are stuck open.
2 Changed plugs with ngk power plugs.
3 switched out fpr and mass air flow.
4. changed about 3 or 4 different pumps.
Changed CAS and adjusted to 15 degrees.
took reading off the mass air flow voltage is between 1.7 to 4.50
5. checked tps.
6.Check voltage to the pump
7.Checked all grounds
8.The only thing i have not done is switch out the ecu.
9. by passed all vacuum lines except for fpr to make sure no vacuum leaks.
10.Check all boost piping up and down.
I think thats about it. any suggestion wud be appreciated i have spent close to 400 bucks tryin to trouble shoot this thing.
I am goin to get my stock ecu back and try that after that i have run out of ideas.

[S14DB]

All I can think is that it's a Knock off Mines ECU and is fucking up.

[street_white180sx]

Buddy your right. i put my stock ecu in the car cleared right out. bey screw them mines computers its enthalpy from now on buddy. I have a slight hesistation but i think its the plugs from how the car wud dump fuel after i while when i had thas POS in.

[ronj]

Go easy with the AV fuel. Its fun to run but it really gums up the inside of your engine!!! Why do you think old cars from the 60's needed valve jobs every 40k miles??? Its all the lead that builds up on them. It leaves nasty deposits everywhere.

[street_white180sx]

yea i know what u mean. i run it mixed though but in the bahamas they only usually have 89 octane not cool. so i mix it with c16 or av gas or 104 unleaded race fuel str8 but that shit is 70 for 5 gallons and c16 is 90 bucks. 89 octane is about 4.20 a gallon over here. av gas is about 4.80 so i rather run the low lead mixed with pump gas. ronj i read a thread wit a post u did and sounds like u had a cut ass on your project i kno the feeling i had quite a cutass myself even though i am an auto tech myself. keep up the good work.