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Thread: Engine miss over 3000 RPM?

  1. #1

    Default Engine miss over 3000 RPM?

    I hoping someone might be able to help diagnose a miss I have under load. The car is:
    1969 Camaro
    6.0 LY6 9.6:1
    Holley HP EFI
    223°/230° @ .050" .601 lift 112° LSA
    Headers
    LS3 Intake
    Edelbrock DBC 92mm throttle body
    87 octane

    The car idle and runs great beside this miss in the middle of the RPM band. I've uploaded a graph below from the datalog.
    What should I start looking for to diagnose this? Any help would be greatly appreciated.
    Last edited by Regal454; 05-21-2013 at 09:45 PM.

  2. #2
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    Quote Originally Posted by Regal454 View Post
    I've uploaded a graph below from the datalog. What should I start looking for to diagnose this?
    What happened at 8.5 seconds into the datalog?
    Did the engine struggle to stay running, then die?
    The air/fuel ratio spiked completely lean.
    Does the datalog display any RPM Errors?
    Inspect the ignition system and spark plugs/gaps.

    Are your Ignition Parameters correctly programmed?
    Ignition Type - "Custom"
    Crank Sensor Type - "LSx 58 Tooth"
    Inductive Delay - "adjusted per application" (← Synchronization info.)
    Timing Offset - "0°"
    Cam Sensor Type - "GM LSx 4x"
    Output Setup Type - "DIS Coil on Plug"
    Dwell Time - "3.5-5.0 msec" (← Read end of page 3 - Link.)
    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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    Quote Originally Posted by Danny Cabral View Post
    What happened at 8.5 seconds into the datalog?
    Did the engine struggle to stay running, then die?
    The air/fuel ratio spiked completely lean.
    Does the datalog display any RPM Errors?
    Inspect the ignition system and spark plugs/gaps.

    Are your Ignition Parameters correctly programmed?
    Ignition Type - "Custom"
    Crank Sensor Type - "LSx 58 Tooth"
    Inductive Delay - "adjusted per application" (← Synchronization info.)
    Timing Offset - "0°"
    Cam Sensor Type - "GM LSx 4x"
    Output Setup Type - "DIS Coil on Plug"
    Dwell Time - "3.5-5.0 msec" (← Read end of page 3 - Link.)
    My ignition parameters are set as you have them listed above, except for the Output Setup Type. Mine was set at "DIS Waste Fire". I just changed it. Do you think that could cause it?

    The engine did stay running. The engine started to break up due to Knock Retard. I have adjusted the Sensitivity and also changed to the 2nd knock Frequency that Holley recommended on the graph but it didn't change. I do not believe it's a knock problem.

    Where in the datalog would I find an RPM error?
    I did check out the plugs/wires/coils. They all look good. Ohm tested the wires and they are fine.

  4. #4
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    Quote Originally Posted by Regal454 View Post
    My ignition parameters are set as you have them listed above, except for the Output Setup Type. Mine was set at "DIS Waste Fire". I just changed it. Do you think that could cause it?
    Well...it certainly can't be good. Why was it set wrong?
    We've discussed your Ignition Parameters before in this thread:
    http://forums.holley.com/showthread....eeded-Starting (Scroll toward end.)

    The engine did stay running. The engine started to break up due to Knock Retard. I have adjusted the Sensitivity and also changed to the 2nd knock Frequency...
    It can be a problem if the amount of Max Timing Retard is set too high in ESC Parameters (Spark ICF).

    Where in the datalog would I find an RPM error?
    View the RPM channel numerical display (left column) while scrolling through the log.
    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.

  5. #5

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    Click image for larger version. 

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    I switched the Output Setup Type to DIS Coil on Plug, tested the car and it still has the same miss.

    My Max Timing Retard is set to 8° with 8° restore per second. What should it be set to?

    The RPM on the datalog graph does appear to vary between 0-3000 while the engine is breaking up.
    Is this an RPM Error? After the break up, the RPM continues in a smooth line as it was before the miss.
    Last edited by Regal454; 05-22-2013 at 10:00 PM. Reason: added data log graph

  6. #6
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    Quote Originally Posted by Regal454 View Post
    Is this an RPM Error?
    That's what I wanted you to ascertain.
    At the left column of the datalog screen, view the RPM channel (numerical display) while scrolling through the log. As you're scrolling through the log, does the "RPM" channel ever display "Error"? The datalog graphs you keep posting, don't include the left column data channel list. It's more helpful if you stop the datalog at the problem area, so we can see the numerical data too.
    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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    Quote Originally Posted by Danny Cabral View Post
    At the left column of the datalog screen, view the RPM channel (numerical display) while scrolling through the log. As you're scrolling through the log, does the "RPM" channel ever display "Error"?
    No, it does not ever display "error" at any of the data points along the RPM line while the engine was breaking up.

  8. #8
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    Quote Originally Posted by Regal454 View Post
    No, it does not ever display "error" at any of the data points along the RPM line while the engine was breaking up.
    OK, in that case, it's probably not a failing crank or cam sensor.
    However, if you're running V2, you should record a System Log to confirm it:
    http://forums.holley.com/showthread....mp-SL-Datalogs (Sensor Diagnostics)
    I'd look into the ignition system components for causing a misfire.
    Ignition misfires cause a false lean condition, which show up as full lean spikes.
    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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    I have a suspicion you may have damaged your LSx ignition coils by firing them in "Waste Fire" mode.
    Waste-spark ignition fires on every compression stroke and exhaust stroke, which may have overheated your coils.
    Also, waste-spark is supposed to operate at 1.8/2.4 msec of ignition dwell, since it's firing twice as often. (LSx - 3.5-5.0 msec dwell time.)
    Holley DIS Dwell Time - "1.8 msec" (early coils) "2.4 msec" (late coils).
    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.

  10. #10

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    Just to update this thread, I did get this problem fixed. I replaced the crankshaft sensor and the sensor connector and the problem cleared right up.

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