Runs fine then dies

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  • #1

    Runs fine then dies

    Hey guys, I've got nistune in my 86 NA2T and I've gotten the car running and idling pretty well. Problem is it only seems to stay that way for a short while.

    Setup:
    -86 NA ECU with nistune, 86T map
    -600cc 3000gt injectors
    -walbro 255lph
    -schneider stage 2 cams
    -AEM UEGO wideband
    -Precision T3/T04 turbo

    First try: got it running, although really rich, set idle and ignition timing. Next morning, loaded same maps and It would run really rough. Reloaded original maps, set injector size and latency, ran ok for a little. Didn't want to idle this time, and eventually sputtered and died. Pulled plugs and they were fouled. No big surprise.

    Today: swapped out plugs, started over with fresh 86T map, set injector size and latency, got car running, tweaked things a little more to get decent afr's and idle, took a little drive, low load only.

    Here's where the problem came up: It did the same thing it did the day before. The car was sitting in my garage idling, I changed latency a bit further to correct mixtures, got them in range. As it was sitting there it started to run a little rougher, and a little rougher, then it seemed to lean out and die. Would not start, sputtered a bit. Ok fine, swapped out the new plugs for the second set I bought, no change. Now it doesn't even seem to want to fire at all.

    Here's what I've checked/what I know:

    -verified that I have spark
    -Verified injectors are pulsing when cranking
    -fuel pump primes and sounds normal
    -Car was at normal operating temp before I even started to drive, verified chts temp with nistune at 85 C.
    -Running exact same bin file as when it was running well
    -Had a very sulfur like smell after is shut off, could I have plugged the cat? (magnaflow high flow cat)
    -sulfur smell only hung around for a little, didn't notice it anymore after continued cranking
    -I can smell raw fuel after cranking
    -Nistune did not lose connection when it shut off
    -MAF signal seemed OK through nistune

    Only thing I regretably don't have is a fuel pressure gauge to verify fuel pressure, which I'll get soon.

    Any ideas?

    I don't see how it would have switched maps or anything as it was already at full operating temp and no knock maps are used. Again, spark and injector pulse are present and I can smell fuel when cranking. I'm pretty lost on this one.
  • #2
    Seems like a fuel related issue to me eric, get a fuel pressure gauge to verify you fp
    87T, My build thread http://z31performance.com/forum/z31-…lee-s-87t-rb26
  • #3
    Threw a fuel pressure gauge on today and fuel pressure is ok as per the fsm. Stays at about 30 psi when cranking. I also threw a new fuel filter on. It sputters and sounds like its firing on one or two cylinders but wont run on its own.
  • #4
    Have you ran trouble codes?
    Have you r & r'd anything ?
    http://z31performance.com/showthread…2-2-(-now-NA2T
    My build thread (:
  • #5
    Runs fine and then dies

    Have the same issue - and no one has ever come up with the answer in the last 9 years I have been fucking with this car. Wish I could help. Starts idles up runs fine -gets to operating temp - starts to sputter - dies - restart runs like its on 2 cylinders and dies. When it cools down will do the same thing all over.
  • #6
    When doing the injector resize and such, remember those injectors are 600cc @ 43.5psi of fuel pressure. Your base pressure is 37psi, so they're effectively a bit smaller.
    - VG30DET (HE341) 86 300ZX - 1982 280ZX Turbo - Headered NA 1986 300ZX 2+2 - 2000 Xterra -
  • #7
    michaelp;345947 wrote: When doing the injector resize and such, remember those injectors are 600cc @ 43.5psi of fuel pressure. Your base pressure is 37psi, so they're effectively a bit smaller.
    http://witchhunter.com/injectorcalc1.php

    553.4cc
    Prius… because Pretentious wouldn't fit across the back of the car…

    Cheap, Fast, Reliable - pick any two

    My 1986 Turbo Build
  • #8
    85zxt3/4;345945 wrote: Have the same issue - and no one has ever come up with the answer in the last 9 years I have been fucking with this car. Wish I could help. Starts idles up runs fine -gets to operating temp - starts to sputter - dies - restart runs like its on 2 cylinders and dies. When it cools down will do the same thing all over.
    Are you saying you have been troubleshooting a problem for 9 years? lol

    List of things on a z31 that can cause it to have intermittent running problems

    ecu
    cas
    maf (can be unplugged, and should run fine to 2k rpm)
    coil
    fuel pump
    relays proving power to ecu/fuel pump/coil
    fuel filter

    it's not a long list, and if you verify fuel pressure, unplug the maf… your really talking about only 3 components…

    The coil is going to be the obvious one, as it's very common for them to work when cold, and fail when hot… it going to work, then start firing on some cylinders, missing others… then give up all together. Then it's going to cool down and start working again.

    Had a coil on my 350z start failing at operating temp, was a bitch to find as the ECU didn't know which cylinder was misfiring, so I had to burn the shit outa my self unplugging and plugging up coils on a hot running engine listening for the stumble to go away. (of course it was the last one/hardest to reach) I don't know why, but a vg30e or vg30de sounds/feels a little rough running on 5 to me, my vq felt like it was coming apart and sounded like a flat 4 when dropping one cylinder, I thought for sure there had to be multiple cylinders dropping, but it was just one.
  • #9
    joey - I had a dtc for the chts but I resolved that issue and no change.

    85zxt3/4 - That's what it did at first, now it won't start at all

    mike p and jaqattack - I compensated for that and entered the corrected injector size. I got it running and tweaked things further for correct mixtures. I died on its own after idling for a bit.

    tempestas - The maf has a good signal through nistune, coil fires good spark, and fuel pressure is ok.


    Here's where I'm at today: Yesterday I forgot to mention when I took the fuel feed line off the rail I noticed a good bit of black crap floating in the fuel when I drained a little bit of it. I of course replaced the fuel filter. The fuel that came out of there was clean. That got me thinking that maybe the injectors are all gummed up. As per my buddy's suggestion I also pulled the lower timing cover to verify valve timing. Spot on. Today I'm swapping the old turbo injectors back on to simplify things and see if I can get it to run that way. Will report back.
  • #10
    Swapped injectors, no change. This thing is really making me wonder. Compression test is next, anyone ever had a motor burn itself up at idle? Lol
  • #11
    still think its a fuel issue, could be spark also
    87T, My build thread http://z31performance.com/forum/z31-…lee-s-87t-rb26
  • #12
    What could it be though? My pressure is at spec, the injectors pulse, replaced fuel filter, I've put the original injectors back on with stock fuel map and still nothing. Also no fuel in the fpr line, and I have verified I have spark.
  • #13
    No vac leaks?
    http://z31performance.com/showthread…2-2-(-now-NA2T
    My build thread (:
  • #14
    just because you see spark doesn't mean the coil is firing each pulse of about 5 times per second at idle with enough power to ignite. If you have a spare swap it out. No reason to check compression if it starts and runs cold. You could also spray some starter fluid in the intake when it starts acting up, if it revs up for a few seconds, you know it's not getting fuel, if it has pressure and you have tried different injectors, the drivers could be going in ecu, if it has no change, it's a spark issue. It's unlikely that it's choking out with too much fuel, you would smell it.
  • #15
    it pulled solid vacuum when running, and nothing was changed so I doubt it.

    Compression is spot on in all six cylinders.

    I have some promising news though! Check this out:

    I was just digging deeper into the spark side of things and found that yes I am getting spark. BUT, when I hooked my timing light to each plug wire I found this:

    cylinder 1: while cranking it would flash twice at a time like tick..tick..................................tick.. tick........................tick…tick........... .. rather than consistently.
    cylinder 3: same as cylinder 1
    cylinder 2: no spark at all, could have sworn i had spark there before…
    cylinder 4: sparked like crazy, almost as fast as it flashes when checking timing at idle. This is where I stopped because this has got to be the problem.

    So my first thought is cap and rotor because based on the evidence it seems they're throwing spark around wherever the hell they please. If that's all this is I'm going to be pissed..Any further suggestions?

    EDIT: Tempestas you called it with spark, I read your post right after I posted this. It appears to have good strength (white/blue in color) but as stated above its all over the place. And hey, never hurts to run a compression check just to be sure, only took around half an hour being lazy about it.
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