Runs fine then dies

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  • #16
    Sometimes we overlook the basics and skip right to the more difficult things when trying to diagnose driveability problems. Always stick to the basics
    87T, My build thread http://z31performance.com/forum/z31-…lee-s-87t-rb26
  • #17
    True, but it was weird that I had visible spark at each cylinder when I first checked it. Only when I went back and used the timing light was I able to get a better look at the pulses for each cylinder. Either way I only spent a day and a half on it so no big deal. I'll pick up a cap and rotor tomorrow and see what happens.
  • #18
    Let me know how it works out. No fault on you.. It's just a learning experience. I do it too. Your persistent though Eric, which is good :-)
    87T, My build thread http://z31performance.com/forum/z31-…lee-s-87t-rb26
  • #19
    Shitty pump.
    Cha iro

    enjoy building it yourself.
    if it fails, fuck it.
    at least you gave it a whirl.
  • #20
    Got it running nicely. Now on with the tuning issues lol…

    I'm currently running stock turbo injectors and turbo map. I actually had to adjust the k value to lean the mixtures out correctly because they were rich, but now it leans out whenever I try to accelerate. Maybe it's just supposed to run that rich at startup (10.5:1), but I got cruising afrs right around 14.7 at operating temp. The other weird thing is the stock injector size on the map is 185, but it's clearly a turbo fuel map, so that's why I resized the injectors. Either way, my laptop is screwed up so I'll have to wait until I get a replacement to mess with it more.
  • #21
    what was causing the issue?
    87T, My build thread http://z31performance.com/forum/z31-…lee-s-87t-rb26
  • #22
    The cap I guess was internally shorted and sending spark all over the place. Fixed now!

    I also got the afr thing figured out from my last post. I think I'll leave my stock turbo injectors in for a while so I get a chance to really get used to nistune before trying the bigger ones again.
  • #23
    Always remember that in warm up mode of the engine the AFR will be significantly richer. As it warms up it gradually leans out the AFR until fully warm, which then should be around 14.5-14.7 at idle.

    1986 300ZX Turbo…sold
    1990 Skyline GT-R…new money pit
    2014 Juke Nismo RS 6-speed…daily
  • #24
    Doubt a rotor and cap will do it. If so u are 1 f'ng lucky guy.

    Shuman47;346020 wrote: 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.
    So many lame sugguestions - whatever Tempestas
  • #25
    So what has happened ?
  • #26
    Tempestas - will try the coil - can't recall but probably have changed it before or swapped it out but can't hurt to try - I am starting a last campaign on this one next week and if that is the problem after all this time and shops and fooling around I would be ever grateful - no one has ever suggested that possiblilty or scenario on the warm issue. Probably because it started and ran who knows why. I was also refurbing 91 240sx Hbk during that period so rather than screw with the Z I spent my time and more money on it. I like it better than the Z so I just let it lay.

    Now that I think about it - new coil - been so long I forgot til I brushed the dust off.
  • #27
    It was the cap. Installed a new one and it is running well now.
  • #28
    Lol. Glad it works. If you have the old one would you mind posting pics of new vs old? Any visible damage you could see that would cause erratic firing? Just in case this crap happens to someone else i'd be good to know what to look for. Thanks.
    vg30'd s13 in progress. Shocks. Pegs. Lucky.
  • #29
    Other than a little scoring around where the rotor contacts the cap there wasn't much visible evidence. I used a timing light to see how erratic the spark distribution was and determined it was the cap.
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