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Thread: New 421 LSx Single Turbo Keeps Dropping RPM

  1. #1

    Default New 421 LSx Single Turbo Keeps Dropping RPM

    So I have a complete new setup. It's a 421 with a 78mm turbo ID1000 injectors Holley Hi Ram, Holley 3 bar MAP, GM sensors. I have the power wires going straight to the battery. Very hard to get it to start, when it does it will pop & bang. When you watch the RPM they will drop to zero and come back up. Sometimes it will run good. I'm so lost, please help. Thank you, Duane

  2. #2
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    Quote Originally Posted by 1970lsxnova View Post
    Very hard to get it to start, when it does it will pop & bang. When you watch the RPM they will drop to zero and come back up.
    I suggest recording a System Log and reviewing it for crank errors.
    http://forums.holley.com/showthread....s-amp-Datalogs (Datalog Information)
    Read Section 18 - System Log, of the "199R10632rev5" PDF document in "V2 Software Update Overview" (in "Holley EFI V2 Instructions").
    May God's grace bless you in the Lord Jesus Christ.
    '92 Ford Mustang GT: 385" SBF, Dart SHP 8.2 block, TFS TW 11R 205 heads, 11.8:1 comp, TFS R-Series intake, Dominator MPFI & DIS, 36-1 crank trigger/1x cam sync, 160A 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, S&W subframe connectors, LenTech Strip Terminator wide-ratio AOD/2800 RPM converter, M4602G aluminum driveshaft, 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.

  3. #3

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    I've done that, what should I look for?

  4. #4

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    I have a download of 1970lsxnova's system log. Unfortunately, I'm not sure what it's actually telling me at this point.

  5. #5

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    Here's a screenshot of what we're seeing in the system log:


  6. #6
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    Quote Originally Posted by Torvus View Post
    Here's a screenshot of what we're seeing in the system log:
    That's a compressed view of a very long System Log. Scroll through it, looking at the CRANK & CAM patterns.
    Zoom In for detail - click & hold at one point of the datalog, and drag & release to another point nearby.
    Replace the crank & cam sensors. I've dealt with plenty of LSx crank & cam sensor failures from helping others.
    http://forums.holley.com/showthread....s-amp-Datalogs (Datalog Information)
    Read Section 18 - System Log, of the "199R10632rev5" PDF document in "V2 Software Update Overview" (in "Holley EFI V2 Instructions").
    May God's grace bless you in the Lord Jesus Christ.
    '92 Ford Mustang GT: 385" SBF, Dart SHP 8.2 block, TFS TW 11R 205 heads, 11.8:1 comp, TFS R-Series intake, Dominator MPFI & DIS, 36-1 crank trigger/1x cam sync, 160A 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, S&W subframe connectors, LenTech Strip Terminator wide-ratio AOD/2800 RPM converter, M4602G aluminum driveshaft, 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.

  7. #7

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    I'm on my third set of sensors. It's getting a little expensive at $200 a set from GM.

  8. #8
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    Quote Originally Posted by 1970lsxnova View Post
    I'm on my third set of sensors. It's getting a little expensive at $200 a set from GM.
    Then that's not the problem. Analyze the System Log to determine if the problem is with the crank or cam sensors/reluctors/gaps/etc.
    You may also want to try selecting "No Cam Sensor" in the EFI software, and see it it runs properly. If so, the problem is with the cam sensor.
    May God's grace bless you in the Lord Jesus Christ.
    '92 Ford Mustang GT: 385" SBF, Dart SHP 8.2 block, TFS TW 11R 205 heads, 11.8:1 comp, TFS R-Series intake, Dominator MPFI & DIS, 36-1 crank trigger/1x cam sync, 160A 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, S&W subframe connectors, LenTech Strip Terminator wide-ratio AOD/2800 RPM converter, M4602G aluminum driveshaft, 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.

  9. #9

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    We have removed the cam sensor no luck. When it does start, it will pop & bang like crossed wires. A few times, it started and ran good.

  10. #10

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    I'm in the same boat. I have a turbo LSX that will start, then immediately shut down. Sometimes will not even start. RPM - no Sync ERR. I have new cam & crank sensors also. Also, removed the the cam sensor from the tuning, and it still will not start.

    EDIT: Problem was wrong base calibration used (Link).
    1987 Monte Carlo SS - LSX BW S475 Turbo Holley HiRam HP ECU
    2004 Subaru WRX STI - Built - HTA3586- Built - Daily Driver - 600whp 93 Octane
    1996 Impala SS Lingenfelter LT4 - T56 - Powerdyne SC
    1995 S10 ZR2 Lifted - LT1 Swapped
    2007 Xterra Offroad - Stock

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