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Thread: Starts, then dies.

  1. #1

    Default Starts, then dies.

    Just did an LS swap into my Chevelle. It fired first start no issues, then looking at the engine I noticed I forgot to plug the brake booster port on the back of the intake. So I put my finger over it and the engine idled low then died. So I plugged it and tried to restart it and it won’t start unless I feather the throttle and it won’t idle either without giving it a like throttle to keep air going into the engine. So this sort of tells me the engine isn’t getting air correct? Is the IAC motor bad? I used an old IAC I got off of a donor engine that was seized and sitting outdoors.

  2. #2

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    If it's DBW, you need to increase the first value in the Pedal vs. TPS table. If it's cable TB, then you might want to crack the throttle blade open a little and do a TPS Autoset. Andrew
    Contact me for remote Holley EFI tuning.
    IG @projectgattago

  3. #3
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    Default

    http://forums.holley.com/showthread....ents-Read-This (Initial Checks & Adjustments - Read Step #3)
    May God's grace bless you in the Lord Jesus Christ.
    '92 Ford Mustang GT: 385" SBF, Dart SHP 8.2 block, TFS T/W 11R 205 heads, 232°-244° duration/.623" lift/114° LSA camshaft, 12:1 C/R, TFS R-Series FTI ported intake, BBK 80mm T/B, Dominator MPFI & DIS, 36-1 crank trigger/1x cam sync, 200A 3G alternator, Optima Red battery, A/C, 100HP progressive dry direct-port NOS, Spal dual 12" fans/3-core Frostbite aluminum radiator, Pypes dual 2.5" exhaust/off-road X-pipe/shorty headers, -6AN fuel system plumbing, Walbro 255 LPH pump, S&W subframe connectors, LenTech Strip Terminator wide-ratio AOD/3000 RPM converter, B&M Hammer shifter, FPP aluminum driveshaft, FPP 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 M/T Street Comp tires.

  4. #4

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    It’s drive-by-cable, forgot to put that in. Also, I don’t have the WBO2 sensor hooked up because I only have open headers right now.

    What’s interesting is that when I had the vacuum leak, the engine started and ran better than when I plugged it. Does that narrow it down to an airflow thing?

  5. #5
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    Quote Originally Posted by JF74CHEVELLE View Post
    What’s interesting is that when I had the vacuum leak, the engine started and ran better than when I plugged it. Does that narrow it down to an airflow thing?
    Yes, maybe you need to open the throttle blade a little more.
    http://forums.holley.com/showthread....ents-Read-This (Initial Checks & Adjustments - Read Step #3)
    May God's grace bless you in the Lord Jesus Christ.
    '92 Ford Mustang GT: 385" SBF, Dart SHP 8.2 block, TFS T/W 11R 205 heads, 232°-244° duration/.623" lift/114° LSA camshaft, 12:1 C/R, TFS R-Series FTI ported intake, BBK 80mm T/B, Dominator MPFI & DIS, 36-1 crank trigger/1x cam sync, 200A 3G alternator, Optima Red battery, A/C, 100HP progressive dry direct-port NOS, Spal dual 12" fans/3-core Frostbite aluminum radiator, Pypes dual 2.5" exhaust/off-road X-pipe/shorty headers, -6AN fuel system plumbing, Walbro 255 LPH pump, S&W subframe connectors, LenTech Strip Terminator wide-ratio AOD/3000 RPM converter, B&M Hammer shifter, FPP aluminum driveshaft, FPP 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 M/T Street Comp tires.

  6. #6

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    I cracked the throttle more and did a TPS auto set, still does the same thing of idling low, I have the idle set to 800 but it was idling 550-600. And if I give it any gas it comes back down and stumbles into a stall.

    EDIT: I’m not sure if this was a right move, but I screwed the IAC motor from the TB housing and turned the key to run, engine off, and the IAC moved then blew the plunger out of it. So it basically exploded. Was this a bad IAC?

    UPDATE: Went to the junkyard and got another OEM IAC, didn’t help. It idles poorly and if you rev it up it comes back down and stalls, horrible throttle response as well.

    Observation: running open headers without the WBO2 sensor I believe the engine is running extremely rich. It’s shooting black smoke out the exhaust and it’s almost unbearable to be around it, it makes tour eyes water up so bad. So I'm taking it to get the exhaust welded up to put the WBO2 sensors in to tune the thing.
    Last edited by JF74CHEVELLE; 06-02-2020 at 07:45 PM.

  7. #7

    Default

    With Closed Loop off, it could also be rich which will make the IAC open further than need be.

    Wait I misread. Is it actually in Open Loop or do you have Closed Loop enabled with the sensor out? If so, it's trying to force fuel in based on a false lean signal.

  8. #8

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    Sorry guys, I messed up. I reviewed the tune in the EFI software and realized I put the wrong MAP sensor and injector data into the Wizard somehow. I fixed it and BAM, it starts, idles and revs. I’m kinda amazed that it ran at all with the incorrect data in the first place. Thank you for all the help.

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