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Thread: Dieseling / run-on?

  1. #1
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    Dieseling / run-on?

    Always something with this damn engine....

    So now I have a slight run on whenever I shut the engine down. More so when ECT is at operating temps, than when cool. I have not had this happen before.

    Changes that I've done are new ID 1000 injectors, and a complete re-cal of VE and MAF. I haven't touched idle speed, and min air is the same. Trims at idle are under 5%. Idle spark is 18. Idle speed is 900.

    I could just start changing things and see what might cure it, but figured I'd get input first. I do not think it is detonation, but run on. My initial thought is to just reduce idle speed to 850. It's at 900 to help get the car rolling from a dead stop without having to feather the throttle so much. (08 Z06 with a healthy cam). It will idle at 800 OK...just a lot of lope.
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    Viewed 51 times. Either I'm asking a really stupid question, and no one feels compelled to respond to such a stupid question, or no one knows what to do.

    Lowered idle speed to 825. Didn't help.

    Lowered min air 20%. Helped a tad, but I still get a couple cylinder fires after hitting the stop button. Now fuel trims are off. Need to revisit MAF/VE cal if I leave min air where it is. Sonofabitch.
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  3. #3
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    I can't understand how it's even possible. Once the power is cut to the ECU, it shouldn't be able to pulse the injectors to put fuel in the engine.

  4. #4
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    If the injectors are spraying more fuel on the wall of the port than the previous ones and the spark plugs are too hot of a heat range this will happen.

    You waited a whole day for a response and complained when one didn't come fast enough. Did you bother to search around?

    Chris

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    Pre-EFI cars use to knock on sometimes (cheap gas and/or carbon buildup). The carbon stays hot (glows like an ember). Gulf had the No Nox commercials going 40+ years ago to solve all your problems by having a horse kick the gas pump. EFI, I dunno....your compression is most likely not nearly as high as a diesel so "A THEORY"....maybe leaking/timing of injectors plus hot carbon buildup ????? If it were me, I would check my injectors and probably do a seafoam or equivalent cleaning attempt. cheers
    2010 Avalanche 4WD; AES 390; Mast LS3 heads; VVT Cam; ported TVS2300; Overdrive 8 rib pulleys; 2.7 snout pulley; ID1000; LS3 TB; WB 450; Twin MM cans; built 6L80; CircleD Triple Disk, CSR flexplate; Trucool 40K; Aeroforce Dual; AFX

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    Quote Originally Posted by granatl View Post
    I can't understand how it's even possible. Once the power is cut to the ECU, it shouldn't be able to pulse the injectors to put fuel in the engine.
    That's what I thought too. No fuel, no spark, why the run on. A quick Google search on this brought up a few theories, one being too much fuel on the piston from running too rich at idle. I having trouble buying that one.

    Quote Originally Posted by Rocko350 View Post
    If the injectors are spraying more fuel on the wall of the port than the previous ones and the spark plugs are too hot of a heat range this will happen.

    You waited a whole day for a response and complained when one didn't come fast enough. Did you bother to search around?
    Not sure if these are spraying more or not. Plugs are NGK TR7IX, which are supposedly one range cooler than OEM. I'm also using MSD coil packs, with 12v direct wiring harness.

    It isn't the "one day" that matters, it's the "over 50 views" without any comment. And yes, I did search. Both this site, and the ol' interweb. Not too many discussions about this happening with EFI.

    Chris[/QUOTE]

    Quote Originally Posted by seven ends View Post
    Pre-EFI cars use to knock on sometimes (cheap gas and/or carbon buildup). The carbon stays hot (glows like an ember). Gulf had the No Nox commercials going 40+ years ago to solve all your problems by having a horse kick the gas pump. EFI, I dunno....your compression is most likely not nearly as high as a diesel so "A THEORY"....maybe leaking/timing of injectors plus hot carbon buildup ????? If it were me, I would check my injectors and probably do a seafoam or equivalent cleaning attempt. cheers
    I ran a 100psi pressure test on the fuel system when I installed it (rails and AN hose). Probably wouldn't hurt to do that again, to make sure the injectors aren't leaking. I have not used Seafoam on a fuel injected engine before, and did not even think of doing that...Thanks.
    When arguing with an idiot, make sure he isn't doing the same thing....

  7. #7
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    Whether or not you found it occurring in efi makes no difference. I usually drop 2 heat ranges when running long tubes , if that's what your running, so the added timing needed when running them doesn't cause a heat issue. Research the Tau fueling. It is the fuel that adheres to the port wall. The 1000's may generate more of that. Its like putting ford 30lbs in a cathederal port motor. Spray pattern to wide. Im not familiar with those injectors, but that's about the only explanation of fuel and ignition source in the chamber. Shut it off in gear and I bet it wont do it.

    Chris

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    Michael, I doubt your ID1000's are leaking, but still needs to be double checked... Most likely it's one of two things. Either your injection timing is so far off that your puddling up fuel on the back side of the intake valves that's continuing to burn in the hot combustion chamber after shut down "happens if too advanced or retarded where fuel actually puddles in the combustion chamber" or you need to go to - Fuel - Transient - Transient Fuel Mass Evaporation - Fuel from Wall Stabilization and play with that setting a little. All though I have never heard of ID injectors having spray pattern change issues and that particular fuel from wall setting is usually for transient fueling? Either this or something is off in the injector data. DSTEK does a lot of these and can hopefully chime in or PM you. I didn't think when you posted having to change your "air tables by increasing them 20%" to fix your fuel trims as much as you did that things were "exactly" right? Usually ID's data is very close... The timing is where I would start after verifying no leakage.

    Hope this helps you out.
    Last edited by GHuggins; 08-16-2015 at 08:47 PM.
    2010 Vette Stock Bottom LS3 - LS2 APS Twin Turbo Kit, Trick Flow Heads and Custom Cam - 12psi - 714rwhp and 820rwtq / 100hp Nitrous Shot starting at 3000 rpms - 948rwhp and 1044rwtq still on 93
    2011 Vette Cam Only Internal Mod in stock LS3 -- YSI @ 18psi - 811rwhp on 93 / 926rwhp on E60 & 1008rwhp with a 50 shot of nitrous all through a 6L80

    ~Greg Huggins~
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  9. #9
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    It would also need an ignition source since he is not high compression like a diesel unless you have a turbo cool down (i.e. like in some after-market alarms) and it runs a couple of more minutes after you take the key out.
    2010 Avalanche 4WD; AES 390; Mast LS3 heads; VVT Cam; ported TVS2300; Overdrive 8 rib pulleys; 2.7 snout pulley; ID1000; LS3 TB; WB 450; Twin MM cans; built 6L80; CircleD Triple Disk, CSR flexplate; Trucool 40K; Aeroforce Dual; AFX

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    Thanks.

    To clarify, it doesn't cough and run on for an extended period. It's more like a couple extra half fires after the stop button is hit. Whereas prior to this occurring, it would shut down immediately.

    My injection timing has remained unchanged, since I moved boundary several weeks ago. I was just trying to note things that have changed very recently that might be causing this.

    My min air was something I've been playing with, trying different things to see the effect it has while cruising at low rpm. I had it artificially high, and that started causing too much hang when in first gear, so now I'm backing it down again. (which is why I was able to lower it 20%).

    Could these MSD coil packs be holding a charge, and providing voltage to fire the plugs, with the ignition off???
    When arguing with an idiot, make sure he isn't doing the same thing....

  11. #11
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    if u change your "min inj pulse width" in the zero rpm column to 0.00 does that help at all..? think i remember reading bout it somewhere and mine was doing a similar thing so i changed that and its fine now, or i was doing some big changes at the time so it could have been a coincidence but thought id mention it anyway cant hurt to try...

  12. #12
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    Thanks for the tip. The ID data did have a value for zero rpm, so I plugged it into the table. I reviewed a stock tune file and there is no value at zero rpm, so I think your idea is a good one to try. I'll report back what the result is.

  13. #13
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    Quote Originally Posted by GHuggins View Post
    Michael, I doubt your ID1000's are leaking, but still needs to be double checked... Most likely it's one of two things. Either your injection timing is so far off that your puddling up fuel on the back side of the intake valves that's continuing to burn in the hot combustion chamber after shut down "happens if too advanced or retarded where fuel actually puddles in the combustion chamber" or you need to go to - Fuel - Transient - Transient Fuel Mass Evaporation - Fuel from Wall Stabilization and play with that setting a little. .
    Zero'ing out the min pulse width Zero rpm cell didn't fix it.

    I also re-visited EOIT. The ID's pulse width is shorter, so I tweaked that a bit to compensate. I had already moved EOIT to fire after the exh valve is shut. Regardless, that didn't help.

    So I got to thinking and looking at the last few calibrations. Sometime within the last few cals, I changed Fuel from Wall Stabilization from 1, to 2. Not real sure why I changed that either....I was experimenting with transients I think, and just forgot to move it back. I'll move it back to 1 and see what happens.

    I'll pressure test the system this weekend, if this last change doesn't help.
    When arguing with an idiot, make sure he isn't doing the same thing....

  14. #14
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    So, when exactly did the problem start?
    2010 Vette Stock Bottom LS3 - LS2 APS Twin Turbo Kit, Trick Flow Heads and Custom Cam - 12psi - 714rwhp and 820rwtq / 100hp Nitrous Shot starting at 3000 rpms - 948rwhp and 1044rwtq still on 93
    2011 Vette Cam Only Internal Mod in stock LS3 -- YSI @ 18psi - 811rwhp on 93 / 926rwhp on E60 & 1008rwhp with a 50 shot of nitrous all through a 6L80

    ~Greg Huggins~
    Remote Tuning Available at gh[email protected]
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  15. #15
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    About a week ago I started noticing it. I take care to give every calibration and log a unique name and date/time stamp, so I can go back and compare to previous cals. But what I do not do, is keep really good notes detailing exactly what changes I make. I need to get into the habit of doing that.

    I tried moving the fuel from wall stabilization back to "1" last night. Didn't help.
    When arguing with an idiot, make sure he isn't doing the same thing....

  16. #16
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    If you saved your different tunes and know when it started, just do a compare. Should show exactly what was changed. Just make sure to go through all of the different sections
    2010 Vette Stock Bottom LS3 - LS2 APS Twin Turbo Kit, Trick Flow Heads and Custom Cam - 12psi - 714rwhp and 820rwtq / 100hp Nitrous Shot starting at 3000 rpms - 948rwhp and 1044rwtq still on 93
    2011 Vette Cam Only Internal Mod in stock LS3 -- YSI @ 18psi - 811rwhp on 93 / 926rwhp on E60 & 1008rwhp with a 50 shot of nitrous all through a 6L80

    ~Greg Huggins~
    Remote Tuning Available at gh[email protected]
    Mobile Tuning Available for North Georgia and WNC

  17. #17
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    Quote Originally Posted by Michael_D View Post
    Always something with this damn engine....

    So now I have a slight run on whenever I shut the engine down. More so when ECT is at operating temps, than when cool. I have not had this happen before.

    Changes that I've done are new ID 1000 injectors, and a complete re-cal of VE and MAF. I haven't touched idle speed, and min air is the same. Trims at idle are under 5%. Idle spark is 18. Idle speed is 900.

    I could just start changing things and see what might cure it, but figured I'd get input first. I do not think it is detonation, but run on. My initial thought is to just reduce idle speed to 850. It's at 900 to help get the car rolling from a dead stop without having to feather the throttle so much. (08 Z06 with a healthy cam). It will idle at 800 OK...just a lot of lope.
    Michael_D,

    I don't have any answers for you, but I can tell you I started experiencing the exact same issue when I switched from stock injectors to ID1000's on my full bolt-on 2007 Z06. The exact same time that I switched the injectors, I also switched to E85. I wasn't sure which of the two was more influencing the problem. However, other than this issue my car runs excellent. Good fuel trims, great idling/street manners (stock cam). My only issue is when shutting the car off it does this quick dieseling (more like a quick stumble).

    I hope you're able to nail down the issue!

  18. #18
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    Quote Originally Posted by GHuggins View Post
    If you saved your different tunes and know when it started, just do a compare. Should show exactly what was changed. Just make sure to go through all of the different sections
    That's exactly what I've been doing, but it's been painful due to my lack of note taking. I have learned the value of doing that! Lol

  19. #19
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    Does the 12v direct wiring harness have a separate relay? If so its probably taking longer to power down and that's why it's running on.

  20. #20
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    any news? I have an )7 with bolt ons and ls9 injectors, runs great, strims are great but it is doing the same thing as yours. I thought it may be the injector spray pattern but you have after market injectors and its doing the same.