Cold start issue and surging

Discussion in 'Z32 Technical' started by tuff, May 2, 2018.

  1. tuff

    tuff Member

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    Cold start issue

    So here we go.....
    Hard to start on cold unless appication of accelerator and then stalls out/rough idle unless i give it some accelerator until warm, then has regular popping (so i figured maybe ignition related). Will then start no worries once warmed up, idles fine, does feel like its bogging down/surging in power throughout the rev range whilst driving

    Mods
    Fresh engine and turbos
    480cc injectors (S15)
    Nismo fpr
    Fmic
    All deletes
    Ebc
    Nisune ecu
    S2 ptu hard wired
    All heat affected connectors appear to have been replaced
    All deletes done

    Things tested

    No boost/vacuum leaks
    Cas tested and swapped
    Fpcu tested/swapped
    Fuel pump tested/swapped
    Iacv tested/cleaned/functioning (conzult)
    Nismo Fuel pressure reg - tested/set at 44 at idle with no vac
    Holds fuel pressure over night so not injector orings
    Plugs swapped to bpr6es coppers for testing at 0.8 (these have white tips starting on them indicating to me im running a bit lean)
    Afm 0.08v with ignition on and around 1.4v at idle (tested 3 different afm)
    Tps 0.42v
    Timing spot on at engine and ecu 15 deg
    Alternor 13.8v at idle, 14.1 ish whilst driving
    Have changed out engine coolant temp sender, reads correctly
    Swapped over s2 ptus
    Throttle bodies clean and correctly adjusted
    Have swapped for factory ecu but over fueling so wont run steadily

    Have had consult on it, no codes

    Does have a weird noise on startup which i suspect is the starter (na box clearanced for tt clutch, 3.8mm spacer in place but might still be a bot tight) and a small exhaust leak from bottom of turbo to dump gaskets

    All pins are fully seated on ecu, no fuses blown.

    Balance test is pretty even all round
    Engine comp test was roughly 165-170 cold when i bought my parts donor car

    I have conducted manual tests on vtc gears, spot on, iacv, follows input values and working faultlessly, i have the idle set at 950rpm atm to compensate for the shit running when cold first start. CTS manually raised above 104 raises idle and triggers fans. Weird thing with iacv is that when electrical load is switched on idle doesn't spike but this might be because its close to what the figure in the tune might be set at.

    It is definitely breaking down under load, has a pretty regular stumble at idle now also (popping away regularly) o2 sensors cycle up and down at 2000rpm, but left bank continuously reads lean where as right side cycles lean/rich (think this might be where part of my issue lies) disconnected o2 sensors and reset ecu to test, seemed to make no noticeable difference at idle (which i expected)

    One weird thing though, engine was running, i pulled the fuel pump/injection main fuse whilst running to try and get the engine to stall out and it continued to run on, never had that happen before. So refitted fuse, went into consult and turned off fuel pump relay expecting the engine to run down ALL the existing fuel in the rails to drop the fuel pressure to zero, it stalled out but still had 35psi fuel pressure between filter and regulator. hmmmm, might throw a walbro 255 in for good measure, and a set of bkr7e coppers at 0.8 that i have here, but im seriously seriously thinking this is all tune related now, the tune on the ecu was done whilst it was an auto and smic. So unknown tune to myself and quite honestly dont trust the tune and who did it. I'll also throw my near new coil packs in for good measure.

    Then i guess injectors out and clean and flow test....


    Anything else i should be looking at, im seriously lost and reaching my breaking (BURNING IT) point
     
  2. tuff

    tuff Member

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    Ok new plugs and different coils (ohm tested 0.7 ohms) are in, plugs removed looked fine. cleaned and retensioned all coil connectors, tps and cas. Air regulator clean and functional.

    Still popping at idle and surging whilst driving.

    Im at a fucking loss, it must be the tune or a dicky injector
     
  3. beaver

    beaver southern zeds

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    pull the rails get the injectors tested, if there good at least you can rule them out. take the car to a nistune shop and have them check out the tune, how long have you had the car, has it always been the same?
     
  4. tuff

    tuff Member

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    Yeah thats my next steps, tune booked for 17th and ill pull the injectors on the weekend to get cleaned and batch tested. I bypassed the fpcu and bumped the fuel pressure up from 44 to 52psi base pressure today and the surging settled down a bit (still there though) so im thinking it might be a partially clogged injector which would possibly explain it being a bitch to start and surging under load. No its a recent acquisition this one.
     
  5. beaver

    beaver southern zeds

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    Ohms test the injectors while there still in the engine, you should see between 10-15 ohms, if you haven't already done it. You've put some effort into this, please post up the outcome when you have it.
     
  6. tuff

    tuff Member

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    Ok i checked injector resistance again (was done prior to install aswell) 10.9 on each one when cold, 12.4-12.8 on them once at operating temp. Ill pull the injectors and get them cleaned/flow tested this week to rule them out and put some new oring on for peace of mind. Its going to be either a slight blockage in a couple OR its in the tune. Definitely no air leaks, its been boost leak tested several times (tiny amount of venting from the recircs which ive found to be pretty normal on these), smoke tested, carby cleaner tested......
     
  7. beaver

    beaver southern zeds

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    The injectors ohms are good... or bad depending how your looking at the situation, you've done just about everything possible imo to sort this out, slightly dirty clogged injectors or a dud tune would be a good outcome after everything.
     
  8. SRB-2NV

    SRB-2NV #TEAMROB

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    My bet is your cold start enrichment table is off causing a lean condition.
     
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  9. East Coast Z

    East Coast Z Well-Known Member

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    Testing fuel injectors with an ohm's meter is only useful if the injector is NOT firing.
    If an injector is NOT firing, a MISFIRE will be present.
     
  10. beaver

    beaver southern zeds

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    Any update tuff ?
     
  11. geron

    geron National Petroleum Equipm

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    You can also test the injectors to see if they click just by putting 12v through their terminals.
    You will know straight away if an injector is not firing. Test them say 10 times each to get some idea/confidence.
    Do it when car is cold, since the issue presents itself then. It could possibly be a sticky injector.

    May I recommend to perhaps check/replace the fuel filter. It might have carbon build up inside it and you won't know until you tap it on the ground or somewhere suitable to see what comes out.

    My Z had these symptoms in the morning many many years ago, it was awful to start and to warm up.
    It ended up being a semi-clogged filter which also affected the longevity of the fuel pump. Once the car was hot though, it worked fine!
    UAS helped me solve this tricky one. Credit where it's due.
     
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  12. geron

    geron National Petroleum Equipm

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  13. rob260

    rob260 Moderator Staff Member

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  14. geron

    geron National Petroleum Equipm

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    Thanks Rob, interesting reading, indeed.
    There is some information regarding the length of the plug and what happens if it sits too far inside the cylinder. It covers everything!
     
  15. stumagoo

    stumagoo Active Member

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    the only time I would recommend copper plugs on a turbo Z is when someone is having issues with the plugs fouling - then while diagnosing the problem I have found coppers are more able to be cleaned and reused where iridiums/platinums have often failed - and even if the coppers do fail they are cheaper to throw away. once the issue is sorted I would always go back to the reccomended plug
     
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  16. tuff

    tuff Member

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    Sorry boys been busy and no update. So, sent the injectors off to be cleaned and flow tested, they were not really to bad, flow patterns a bit better after cleaning but flow rates were pretty even before and after, two injectora 4 and 6% variation but that really is negligible and not going to cause these issues. The s2 ptu connectors i found looked like they had been soldered on with a potato by a meyth head, i kid you not. They looked like they had splayed the wires, pushed them together, tried to close them up, put a drop of solder on top and tried to melt it with a lighter, and that is being polite about my description.... aome people should be sterilised at birth. I decided once i seen this and a couple other sub par attempts at the wiring that i would bite the bullet, pull the trigger and just replace the harness with a new lhd us one i had floating around. Well believe it or not, that and the injectors didnt fix the problem . I sat and had a bourbon or two and kept hammering the interwebs because im like a dog with a bone when something keeps eluding me. Figures id reset the throttle bodies again, but they were fine, and then I found an old post from someone regarding intermittent misfires and ignition breakdown, they spoke about the ignition relay upgrades and replacement. Yeah fucking right, ive got 12v at the coil so this cant be at play. Well, for two seconds work I figured it cant hurt. Well I'll go he, it fucking sorted the breakdown issue. Now i will still hunting the issue of the lag in power and late boost, so i bit the bullet and swapped out the stupidly massive fmic which i secretly knew deep down was a power sapping heap/beast, and its running pretty damn good, just desperately in need of a tune
     
  17. tuff

    tuff Member

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    Sorry boys been busy and no update. So, sent the injectors off to be cleaned and flow tested, they were not really to bad, flow patterns a bit better after cleaning but flow rates were pretty even before and after, two injectors 4 and 6% variation but that really is negligible and not going to cause these issues. The s2 ptu connectors I found looked like they had been soldered on with a potato by a meth head, I kid you not. They looked like they had splayed the wires, pushed them together, tried to close them up, put a drop of solder on top and tried to melt it with a lighter, and that is being polite about my description.... some people should be sterilized at birth. I decided once I seen this and a couple other sub par attempts at the wiring that I would bite the bullet, pull the trigger and just replace the harness with a new lhd US one I had floating around. Well believe it or not, that and the injectors didnt fix the problem.

    I sat and had a bourbon or two and kept hammering the interwebs because im like a dog with a bone when something keeps eluding me. Figured I'd reset the throttle bodies again, but they were fine, reset tps higher right on tps closed switch activation etc.. and then I found an old post from someone regarding intermittent misfires and ignition breakdown, they spoke about ignition relay upgrades and replacement. Yeah fucking right, I've got 12v at the coil so this cant be at play. Well, for two seconds work I figured it cant hurt. Well I'll go he, it fucking sorted the breakdown issue.

    Now I was still hunting the issue of the lag in power and late boost, so I bit the bullet and swapped out the stupidly massive fmic (which I'll admit looked really nice and was spectacularly engineered, I suspect by Chris EZZUPTURBO during his ownership) which I secretly knew deep down was a power sapping heap/beast, and its running pretty damn good now, just desperately in need of a tune
     
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  18. stumagoo

    stumagoo Active Member

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    starting to come together buddy.
     

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