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Thread: Limp mode?

  1. #1

    Default Limp mode?

    After reflashing the TC and advancing the cam 2°, I can no longer make a full pass. Good burn out, good 60', then the engine seems to go into a limp mode at around 6-6.3K in first gear. Throttle pedal goes dead for 4-5 seconds as the car is idling down the track, TPS tracks pedal travel, then engine starts responding again, as long as I don't go back to full throttle, at which point it will go back into limp mode. Fuel pump is running the whole time, fuel pressure follows Boost. This is a SBF, ProCharged, Holley HP with CNP and Big Wire Kit, any help would be greatly appreciated.

  2. #2
    Join Date
    Dec 2009
    Location
    Connecticut
    Posts
    27,483

    Default

    You should probably record & review a short datalog of this occurrence.

    This is a copy & paste from one of my other posts:
    Originally Posted by Danny Cabral
    For further assistance, post your Global File and a short datalog of this occurrence for us to analyze.
    Also, review the datalog and inform us of exactly where in the datalog (time/seconds) the problem occurs.
    Datalog & Global Files must be linked to a document hosting website. I use Dropbox.com.
    Files can also be "zipped" (compressed zipped folder) & attached directly to a forum post ("Go Advanced" & "Attachments").
    Your Global File is in the "Documents", "Holley", "HEFI V5", "Global Files" folder (.hefi file).
    Your Datalogs are in the "Documents", "Holley", "HEFI V5", "Datalogs" folder (.V5.dl file).
    Someone will analyze/troubleshoot the problem & offer advice. Also, ensure all this is right:
    http://forums.holley.com/showthread....ents-Read-This (Initial Checks & Adjustments - Read Steps #1-#6!)
    Overlay the datalog onto your Global File, and pay special attention to the center paragraph in blue print:
    Originally Posted by Danny Cabral
    Quick Datalogger Information:
    Always provide data, not just symptoms. Is the AFR & ignition timing optimized? Overlay the datalog onto your Global File.
    Ensure the Target A/F Ratio table is properly programmed for your engine. Ensure the ECU is "Learning" (Learn Table LINK).
    Scroll through the datalog to the problem area. Then look exactly where this happens on the Base Fuel & Timing Tables. Scrutinize:
    RPM, MAP, MAT, TPS, CTS, IAC, Target AFR, AFR Left, CL Comp, Ignition Timing, Duty Cycle, Fuel Flow, Fuel Pressure & Battery.

    Using the Holley EFI software (LINK), look at where the live cursor moves to during this occurrence, and
    manually tune that area of the Base Fuel Table (enrich or lean) & Base Timing Table (optimize ignition timing).


    I find the most helpful datalog function, is overlaying the datalog on your Global File.
    I'm in the habit of using the datalog Overlay feature every time I review a datalog.
    Click on "Datalog" (on the top Toolbar), "Activate Overlay", then "Open Data Log".
    You can literally "playback" a recorded event, and watch it as it happened on any screen.
    Minimize (shrink) the datalog window, and move it to the bottom of any Global File screen.
    Then click & scroll anywhere on the datalog, and watch it playback on your Global File (EFI software).
    http://documents.holley.com/techlibr...9r10543rev.pdf (Holley EFI Datalogger Instructions)
    https://forums.holley.com/showthread...s-amp-Datalogs (Datalog & System Log Information - Read "NOTES")
    https://www.youtube.com/watch?v=iqHO...C6FEA0BB99AF17 (How To Record & Email A Datalog)
    https://www.youtube.com/watch?v=q7OZUXLRS1Q (How To Record A System Log & Diagnose A No-Start Condition)
    https://forums.holley.com/showthread...7531#post77531 (Closed Loop Datalog Tuning - Posts #2, #4 & #6)
    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.

  3. #3

    Default

    I datalog every pass. What I see by Overlaying the datalogs is that the ignition is being shutdown at an average of 6400 RPM with no throttle response until RPM goes below 2100 RPM. It's as if a rev limiter is taking over. I have the Main Over-Rev set at 8000 RPM and no Rev Limiter #1 or #2 enabled. Thinking maybe a program reset and update from V4 to V5?

  4. #4
    Join Date
    Nov 2020
    Location
    Youngstown OH
    Posts
    12

    Default

    Any luck with this? I'm experiencing something similar. With all safeties disabled, throttle goes dead with TPS never missing a beat, then cuts RPM till about 3000 even with TPS pegged at 100% won't come back till engine speed drops to below 2500ish RPM. Datalogs no faults, datalog indicates nothing abnormal.

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