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Thread: New engine starts, but runs terrible within a few seconds.

  1. #21
    Join Date
    Dec 2009
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    It's TBI...remove the air cleaner and look down the throttle bores while the engine is idling.
    May God's grace bless you in the Lord Jesus Christ.
    '92 Ford Mustang GT: Dominator MPFI & DIS, A/C, Spal dual 12" fans/3-core Frostbite aluminum radiator, Pypes dual 2.5" exhaust/X-pipe/shorty headers, 100HP progressive dry direct-port NOS, 160A 3G alternator, Optima Red battery, LenTech Strip Terminator wide-ratio AOD/2700 RPM converter, FRPP 3.31 gears, Cobra Trac-Lok differential, Moser 31 spline axles, '04 Cobra 4-disc brakes, '93 Cobra booster & M/C, 5-lug Bullitt wheels & 245/45R17 tires.

  2. #22
    Join Date
    May 2019
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    Vancouver, BC, Canada
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    Quote Originally Posted by Danny Cabral View Post
    I simply answered the question in post #16. If you don't know to use the 2D Table, you'll need someone to help you.
    Then I guess I asked the wrong question, was just verbalizing some observations that I had in the hope it might trigger some helpful input or questions to diagnose this puppy.
    - As an expert, where do you think the issues are?
    - Does one normally need to go in and tweak the tables?
    - Earlier you suggested finding out why it's not running in Closed Loop. I've verified with the handheld that Closed Loop & Learn are both enabled, so what other possibilities are there that we should chase down?
    Thanks, Steve

  3. #23
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    May 2019
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    Quote Originally Posted by Danny Cabral View Post
    It's TBI...remove the air cleaner and look down the throttle bores while the engine is idling.
    Yes, done. I saw articles talking about injectors that didn't work so it was one of the first things I did. All four give the prime shot and work once the engine starts up.

  4. #24
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    Quote Originally Posted by FF33ROD View Post
    - As an expert, where do you think the issues are?
    In post #16, I only answered the timing question. I don't know what else is potentially wrong.

    - Does one normally need to go in and tweak the tables?
    EVERY Sniper EFI user should use the 2D Tables (Base Timing Table & Target Air/Fuel Ratio table).

    - Earlier you suggested finding out why it's not running in Closed Loop. I've verified with the handheld that Closed Loop & Learn are both enabled, so what other possibilities are there that we should chase down?
    Closed Loop & Learning happens at all RPM, provided the Closed Loop/Learn Parameters are programmed as such.
    The Coolant Temperature Enrichment % & A/F Ratio Offset tables must be at 100% & zero to enter Learn mode.
    You'll need to reconfigure these tables if you're running the engine colder than what the base calibration specifies.
    May God's grace bless you in the Lord Jesus Christ.
    '92 Ford Mustang GT: Dominator MPFI & DIS, A/C, Spal dual 12" fans/3-core Frostbite aluminum radiator, Pypes dual 2.5" exhaust/X-pipe/shorty headers, 100HP progressive dry direct-port NOS, 160A 3G alternator, Optima Red battery, LenTech Strip Terminator wide-ratio AOD/2700 RPM converter, FRPP 3.31 gears, Cobra Trac-Lok differential, Moser 31 spline axles, '04 Cobra 4-disc brakes, '93 Cobra booster & M/C, 5-lug Bullitt wheels & 245/45R17 tires.

  5. #25

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    Quote Originally Posted by FF33ROD View Post
    Then I guess I asked the wrong question, was just verbalizing some observations that I had in the hope it might trigger some helpful input or questions to diagnose this puppy.
    - As an expert, where do you think the issues are?
    - Does one normally need to go in and tweak the tables?
    - Earlier you suggested finding out why it's not running in Closed Loop. I've verified with the handheld that Closed Loop & Learn are both enabled, so what other possibilities are there that we should chase down?
    Thanks, Steve
    It isn't a Sniper tuning problem. You can't program a Sniper to give you 4 black plugs and 4 white plugs. You have a mechanical issue. It is possible that half of the Sniper injectors are shutting off when the engine gets warm, so you might want to double check that. You could rig up a cell phone or Go Pro over the throttle bores and rev the engine up when warm. That should show you what's going on. If it isn't the throttle body then it's something with your intake manifold.

    If all four injectors are working, but you have 4 black plugs and 4 white plugs, then you have some other sort of an issue. Could be a vacuum leak on one side or something like that. Maybe you left the ports in the back of the Sniper open? Your PCV isn't hooked up? You have some sort of mechanical problem, so you'll just need to look at everything.

  6. #26
    Join Date
    May 2019
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    Vancouver, BC, Canada
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    All the ports are plugged as they come packaged from Holley. I was thinking that if it were an ignition issue (multiple firings caused by interference or something) where the intake valve was open, it might mess up the other cylinders on the same plane, but maybe that's not likely or possible. In any case, I'll drain the cooling system and tear it down to take the intake off. Need to order new gaskets. Again, your help and suggestions are very much appreciated. Steve

  7. #27
    Join Date
    May 2019
    Location
    Vancouver, BC, Canada
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    10

    Default One of life's more embarrassing moments.

    Well gentlemen, as the title suggests, I found the problem and it's one of life's more embarrassing moments. When I discovered it, I laughed myself silly.

    I was looking around the Sniper and intake manifold contemplating on what to disconnect and in what order to get the manifold removed. The rear bolts on the manifold are quite close to the firewall and I was contemplating access when I glanced at the backside of the intake manifold plenum just an inch or two below where the Sniper mounts, and there it was staring at me in the face, an unsealed port into the intake manifold. I don't remember ever seeing it before and I have no idea what you would use it before unless you can use that for the PCV instead of a port on the carb, but I hadn't sealed it.

    So, after I finished laughing at myself, I found a plug, added a thread sealer, put it in and gave it a crank. Started up and purred like it should. I now have the idle and timing setting stuff to do and check, but major hurdle overcome. Thank you for all your help and sorry to waste your time, but maybe you can get a bit of a giggle out of it as well. Definitely a newb moment. Cheers, Steve

  8. #28

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    Yeah, I was convinced that you had a big vacuum leak after you posted the picture of the plugs. That was about the only thing that made sense. Glad you found it. If you spend very much time on this forum you'll learn that most of the "problems" posted on here are actually user error. The hard part is to get the user to actually go find their error. Some people get so locked into blaming the Sniper that they refuse to go back and review the basics. Congrats on actually following through with the debug process.

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