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Thread: AFR goes dead lean at 5200 RPM under full throttle.

  1. #11
    Join Date
    Dec 2009


    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
    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: (Initial Checks & Adjustments - Read Steps #1-#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.

  2. #12

    Hopefully this works. 9.598 milliseconds is where the incident occurs.
    Last edited by rm23u0a; 11-27-2020 at 10:56 PM.

  3. #13


    @rm23u0a: Yes, you just tell it that you want to run a shorter datalog. How long are you running the datalogs for right now? They shouldn't need to be more than 15 or 20 seconds long. You can also reduce the number of points per second.

  4. #14


    They're running from 50% throttle or greater till I shut it off. I'll mess with the parameters next time I'm at the track. For now per Danny's instructions, I was able to crop the existing ones I have. I have posted them in Dropbox above. Please feel free to take a look.

  5. #15


    Yeah, they'll get really long if you just let them run. Typically you can shut the datalog down after the run is over, since the drive back to the pits information isn't worthwhile.

  6. #16


    So anyone want to take a look at my datalog and give me some leads?

  7. #17


    Check your fuel system. Fuel pressure starts to get unstable around 6.5 seconds and Fuel Flow almost cuts off about 9 seconds. Injector Pulse Width is still commanding until you lift around 9.4 seconds. Maybe a fuel pickup issue or hose collapsing?

  8. #18


    So I thought I’d update this thread. I changed from a non-resistor spark plug to a resistor plug. Last weekend I made four passes with no problem. The first time in over a year. Thanks for all the advice. Oh and my fuel pressure variances were due to a remote mounted sensor that wasn’t bled.

  9. #19


    Good to hear! Thanks for the follow up

  10. #20


    Nice work on finding the problem. Neither of those problems were very obvious. EFI engines should always have resistor plugs in them since non-resistor plugs can cause weird issues. Your issue didn't seem like an RFI type of problem, but if that solved it then great. I wouldn't have thought of bleeding the sensor, but I can see how that could cause a problem. Hopefully you got all of the bugs out of the system and can enjoy racing.

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