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Thread: Sensors in play at startup (383 SBC/HSR).

  1. #1

    Default Sensors in play at startup (383 SBC/HSR).

    So I'm having a hot start issue. When cold the car starts up just fine, but once warm the car will not start unless you give it some throttle. This is a throttle cable setup on a 383 SBC with a Stealth Ram. It's got me thinking about what sensors the HP setup is looking at during startup. Pushing the throttle is obviously allowing more air into the engine at startup, but is the TPS at play and the ECU is now saying add fuel too? I either don't have enough air or I don't have enough fuel once hot. I just can't figure out which is being added when I push the throttle open on startup. I'd think Startup Enrichment would ignore TPS and just use a predefined fuel map based on CTS and maybe IAT. Under that thought process I'm adding air at startup so I need to back out fuel at higher sensor temps and/or I need to mess with the IAC motor to allow more bypass at idle. Thoughts?

  2. #2
    Join Date
    Dec 2009


    If you take the time to study this, you'll be a startup tuning expert, and read the "TIP" in post #6: (Good Starting Advice Thread - Especially posts #2, #4 & #6.)

    Turn the ignition key on, wait for the WBO2 sensor to display AFR, then start the datalogger & engine.
    This allows you to determine if the Cranking Fuel and immediate engine AFR is excessively rich or lean. (Related Cranking/Startup Tuning Post)

    You can only tune the Startup Enrichment parameters after the Learning has self-tuned the Base Fuel Table and if the Coolant Temperature Enrichment & A/F Ratio Offset tables are acceptable. This is because the aforementioned parameters & tables are modifiers of the Base Fuel Table. Exception: Cranking Fuel (lb/hr), Cranking Timing & IAC Parked Position %, because they function independently under 400 RPM (or whatever your "Crank To Run RPM" is). FYI: The "Crank To Run RPM" parameter (in Ignition Parameters) is not your actual cranking RPM when starting the engine.

    You should probably record & review a short datalog of this occurrence too. Overlay the datalog onto your Config 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 Config 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 Sniper 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 Config 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 Config File screen.
    Then click & scroll anywhere on the datalog, and watch it playback on your Config File (EFI software). (Holley EFI Datalogger Instructions) (Datalog Information - Read "NOTES") (How To Record & Email A Datalog) (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, Holley Dominator MPFI & DIS, 36-1 crank trigger, 1x cam sync, 200A 3G alternator, Optima Red battery, R134a A/C, 100HP progressive dry direct-port NOS, Spal dual 12" fans, Frostbite 3-core 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, BMR upper & lower torque box reinforcements, LenTech Strip Terminator wide-ratio AOD, 3000 RPM converter, B&M Hammer shifter, Stifflers trans crossmember & driveshaft safety loop, 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


    Most likely your throttle blades are not adjusted properly, and the Cranking Fuel & IAC Parked Position are not right. Andrew

  4. #4


    The big difference between cold start and warm start is the IAC Position. There's a map for IAC Position so you can easily customize it. The default numbers are usually too low for a big engine. The first EFI engine I worked on was a 512 inch big block that started fine cold, but wouldn't start when warmed up. Pulled my hair out for a few hours then called an expert who told me to increase the IAC Position at higher temperatures. Made that change and the engine started immediately. So sometimes the difference between not running and running great is just a mouse click.

  5. #5


    This is awesome. I was fairly sure this is an air issue and not fuel. I'll play with the IAC Parked Position and see if I can improve things a bit.

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