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  1. #1

    Still fighting a lean misfire.

    The Car: 1989 Nissan 240sx - Aristo 2JZ-GTE - AEM EMS V2 - Single turbo kit setup - FIC 750cc injectors and Rail - Aeromotive FPR - Deatschwerks DW300 fuel pump - Russell fuel filter.

    Part Replaced : New battery (February 2014), New NGK 3330 plugs gapped at .028 (May 2014) , Newer low miles coilpacks (August 2013) New coil pack connectors & Terminals (August 2013) AEM 3.5bar Map and IAT sensor (January 2012) Fuel system (Spring 2012)

    Parts Tested: Unplugged front cam position sensor #1 car ran dramatically worse. so that seems to be ok, will test resistance on it still. Tried known good working ignitior and noise filter, Swapped out to another set of NGK 3330's @.028 Gap. Tested the AEM Map sensor it testeed within range. The IAT sensor tested slightly off so i got a new IAT sensor that tests closer to spec but still not 100% spot on where AEM states it should be, car ran slightly better. Tried known good working Wideband 02 sensor no change, Replaced injector o-rings and bungs after finding out there was a leak when i sprayed choke and carb cleaner around them the car ran different. Once fixed i tried the same test and there was no change in the way the car ran when i sprayed choke and carb cleaner car seemed to run slightly better but only for a little while. Car holds 43-44psi of fuel pressure at idle and climbs when the car comes into boost Fuel pressure doesn't change when the misfire occurs. Tested the new battery that see's 12.8-13.0 Volts when the car is running misfire or not.

    Thing's i haven't checked: Having he injectors cleaned and flow tested, but they are only a couple years old and have maybe 2500 miles on them. Crank position sensor, ECU itself, Wiring harness, and the fuel pump (Though the fuel pump if going bad i would see a loss of fuel pressure i believe?

    The issue: The misfire/lean issue started last fall (September-October 2013) It was relatively cold out and i noticed it was missing and running lean so i took the car home and thought the 40 degrees. weather is the issue as the car doesn't typically see temps that cold and it was tuned in mid-high 90 degree temps. Took the car out this spring with No changes other than a new battery and it does the same thing, car seems to run better when the engine is cool, But once water temps start getting into the 155+ degree range the misfire happens slightly at idle (AFR goes between 15.8 - 17+ AFR) does the same thing on light and partial throttle. But the car seems fine when you go WOT or give it a certain amount of gas, but almost on tip in it goes lean and trying to maintain speed then it goes real lean and misfires. Sometimes when the car is idling and the AFR's go real high (16-17 Range) the car will die. But it will start back up no problem.

    Could bad gas be the issue? We put gas in it just before last fall, then drained it out for world of wheels then put new gas in the car in April, been troubleshooting ever since.
    Quote Originally Posted by 88Nightmare
    its always winter on bcm!

  2. #2
    Praise the Lord. Reverend Cooper's Avatar
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    you sure it doesnt have a vacuum leak some place

    special thanks to: Marv @ C&M performance 262-993-6605

  3. #3
    Quote Originally Posted by Reverend Cooper View Post
    you sure it doesnt have a vacuum leak some place
    Don't believe so. Only have a few vacuum lines
    Wastegate-Turbo Which is fine.
    Turbo to intake manifold - Which is fine as well.
    FPR to intake manifold - Which is newly replaced and tight
    Blow off valve to intake manifold, which is relatively new and in good shape.

    I will go back through and check them. The intake manifold didn't seem to leak when i sprayed some Choke and carb cleaner by it, i'll give it another shot.

    Thanks Coop.
    Quote Originally Posted by 88Nightmare
    its always winter on bcm!

  4. #4
    You didn't say anything about a boost leak test. Did you do one?
    TaninAutoElectronix
    90 Mitsubishi Mirage 9.9@146, 800awhp
    04 Gallardo
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  5. #5
    I haven't done one yet, i will try that on thursday.
    Quote Originally Posted by 88Nightmare
    its always winter on bcm!

  6. #6
    have pot, will stir WickedSix's Avatar
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    i know pretty much zero about these engines but is the EGR deleted, blocked, etc. Could there be a leak on a block off on intake manifold? are there any npt fittings in the intake side that are dissimilar metal where temperature could introduce a small vac leak?

  7. #7
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    Can you narrow down to which cylinder is misfiring? I assume you have a boost gauge, what happens with the vacuum when it shoots lean at idle. Also what is your normal vacuum at idle? What do the new plugs look like? When you did the wiring for the swap did you use any butt connectors or did you solder them all? Would be nice If you could data log before and after this happens.

  8. #8
    Updates?
    TaninAutoElectronix
    90 Mitsubishi Mirage 9.9@146, 800awhp
    04 Gallardo
    04 Lexus LS430
    71, 96, 94 Land Cruisers

  9. #9
    Quote Originally Posted by WickedSix View Post
    i know pretty much zero about these engines but is the EGR deleted, blocked, etc. Could there be a leak on a block off on intake manifold? are there any npt fittings in the intake side that are dissimilar metal where temperature could introduce a small vac leak?
    No leaks from the intake manifold


    Quote Originally Posted by spooln30 View Post
    Can you narrow down to which cylinder is misfiring? I assume you have a boost gauge, what happens with the vacuum when it shoots lean at idle. Also what is your normal vacuum at idle? What do the new plugs look like? When you did the wiring for the swap did you use any butt connectors or did you solder them all? Would be nice If you could data log before and after this happens.
    Vac is usually in the 18-20 Range, when the car starts to miss it starts to lower the rpm and thus lowering the vac. The place that wired the harness up originally did both butt connectors and solder.

    Quote Originally Posted by LIL EVO View Post
    Updates?
    Did a boost leak test, found i had a tore coupler from the hot side to the intercooler itself. replaced that and found there was a vacuum cap that was loose on manifold, fixed that issue. Now it seems to run lean all the time.. .
    Quote Originally Posted by 88Nightmare
    its always winter on bcm!

  10. #10
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    Is it possible that the car was tuned with a vacuum leak? Now that you fixed the leaks and it's running lean. What are the afrs now?

  11. #11
    Post whore
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    Actually wait, if that was the case then it would be too rich now. Oops. Lol

  12. #12
    The Yellow Tie Fighter
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    Check supply voltage to injectors and coils. Verify ground resistance to ignitor at the least. Best to check with a scope on the dyno.

    Could also be the tune but it can be hard to get a solid AFR from it if its breaking up so that can be sort of chicken and egg.

  13. #13
    Quote Originally Posted by WhatsADSM View Post
    Check supply voltage to injectors and coils. Verify ground resistance to ignitor at the least. Best to check with a scope on the dyno.

    Could also be the tune but it can be hard to get a solid AFR from it if its breaking up so that can be sort of chicken and egg.
    Thanks Murray.I've checked a few other things, replaced and tested stuff, car seems to run ok now, Just starts and runs around 14.7ish then dips way down into the low-mid 10's once the car gets warmed up the afr's go pretty much full lean. I'm leaning on it being a tune issue just based off the fact that there was so many little issues that have since been fixed/solved. So if the tune was tuned around an issue and the issue got worse, now it's fixed in theory i believe the tune would now be off. Correct?
    Quote Originally Posted by 88Nightmare
    its always winter on bcm!

  14. #14
    Jack of all Asses Wagonbacker9's Avatar
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    Quote Originally Posted by Flicktitty View Post
    Thanks Murray.I've checked a few other things, replaced and tested stuff, car seems to run ok now, Just starts and runs around 14.7ish then dips way down into the low-mid 10's once the car gets warmed up the afr's go pretty much full lean. I'm leaning on it being a tune issue just based off the fact that there was so many little issues that have since been fixed/solved. So if the tune was tuned around an issue and the issue got worse, now it's fixed in theory i believe the tune would now be off. Correct?
    If issues were "tuned in" its certainly at least suspect and worth having someone look at it (they hopefully should be able to do some diagnostics with the electronics too to help point you in the right direction?). I don't know the AEM system at all so I don't know how much it can self-correct.
    2006 M6 QSM GTO SOLD
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  15. #15
    Too many variables aem. Is it set up for o2 feedback to "self maintain"? If so that could be a problem if the sensor is going bad or there's now an exhaust leak.
    TaninAutoElectronix
    90 Mitsubishi Mirage 9.9@146, 800awhp
    04 Gallardo
    04 Lexus LS430
    71, 96, 94 Land Cruisers

  16. #16
    Assuming whoever tuned it didn't lock it, if you want to drive down here some day I can take a look at the car/tune for free. Or you can email me the tune and I'll look it over to see if there's anything wacky.
    TaninAutoElectronix
    90 Mitsubishi Mirage 9.9@146, 800awhp
    04 Gallardo
    04 Lexus LS430
    71, 96, 94 Land Cruisers

  17. #17
    Quote Originally Posted by LIL EVO View Post
    Too many variables aem. Is it set up for o2 feedback to "self maintain"? If so that could be a problem if the sensor is going bad or there's now an exhaust leak.
    Wideband is new (as in like 15 minutes of run time as of now) The Car with the new and old sensor ran the same way.
    Starts and runs at 14.5-14.9 then it riches up to
    11.4 - 11.6 @ 115F (water temp)
    12.2 - 12.4 @ 130F (water temp)
    14.3 - 14.5 @ 150F (water temp)
    14.8 - 14.9 @ 160F (water temp)
    15.5 - 15.8 @ 165F (water temp)
    16.0 - 16.2 @ 170F (water temp)
    17.0 - 17.5 @ 175F (water temp)
    17.5 - 17.8 @ 178F (water temp)
    17.8 - +++ @ 170F (water temp)

    After doing a couple of free rev's the car seems to have a big idle surge. and has a rough idle. Here is a screenshot of the fuel map,



    Quote Originally Posted by LIL EVO View Post
    Assuming whoever tuned it didn't lock it, if you want to drive down here some day I can take a look at the car/tune for free. Or you can email me the tune and I'll look it over to see if there's anything wacky.
    The tune isn't locked, Sound Performance doesn't believe in doing that. I've talked to Larry and he insists it's not the tune but i just have a hard time believing that anymore at this point in time. Where are you located now a days? Not sure how much i want to drive the car if it's running bad. but it might be worth doing cause i'm just about stumped.
    Quote Originally Posted by 88Nightmare
    its always winter on bcm!

  18. #18
    6 mile and 32, right off the lake.
    TaninAutoElectronix
    90 Mitsubishi Mirage 9.9@146, 800awhp
    04 Gallardo
    04 Lexus LS430
    71, 96, 94 Land Cruisers

  19. #19
    If it ran fine when tuned then usually the tune isn't the issue. The tune can't "go bad" without external changes.
    TaninAutoElectronix
    90 Mitsubishi Mirage 9.9@146, 800awhp
    04 Gallardo
    04 Lexus LS430
    71, 96, 94 Land Cruisers

  20. #20
    Quote Originally Posted by LIL EVO View Post
    6 mile and 32, right off the lake.
    hmm that might be a bit of a stretch to pussy foot the car down there, i'll see what i can do, otherwise i'm more than willing to compensate your time/travel.

    Quote Originally Posted by LIL EVO View Post
    If it ran fine when tuned then usually the tune isn't the issue. The tune can't "go bad" without external changes.
    Correct me if i'm wrong, but say the car had a small boost leak, or a sensor was going bad (let's say water temp sensor) And the car was tuned. The sensor condition gets worse and the boost leak get's bigger. Than you repair the boost leak and the sensor. and now the car runs goofy cause the car's tune was done when the voltage to a sensor or the sensor was reading wrong, and it was seeing air via a boost leak and now neither of those problems are present, wouldn't that make the tune "off"

    Maybe i'm looking at it from the wrong direction, i'm just so fed up with the car and the issue as i can't seem to make any headway on the problem.
    Quote Originally Posted by 88Nightmare
    its always winter on bcm!

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