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Thread: Erratic readings barely running.

  1. #1

    Default Erratic readings barely running.

    Would a failed/failing oxygen sensor possibly cause all my sensor readings to jump erratically? I had trouble getting the car started yesterday during a trip, but finally got it and it ran very poorly to get home, including stalling a couple times. While running and even with it key on engine off it is reading random AFR 12- 35 fuel pressure, coolant and air temp is bouncing all over, injectors showing a duty cycle % even with the engine not running. The IAC is constantly adjusting presumably chasing the other numbers changing. I've unplugged one at a time everything but the WBO2 sensor at this point. No apparent rubbed spots on the harness though there is some I cannot see without pulling it out completely.
    Day 2:
    Today I also unplugged the WBO2 sensor with the same result. I currently have all sensors unplugged from the ECU. A new symptom is it searching, but not being able to find and sync to the ECU on the 3.5" TSLCD handheld. When it does this and you shut the key off the handheld stays on until you either disconnect the battery or unplug the main ECU power connector. To further troubleshoot I got it into that state again key off handheld staying on Searching For ECU. I disconnected the P1B Connector which appears to be all outputs, and the handheld shuts off. If i plug the P1B connector back in the handheld comes back on. P1B appears to be all outputs? So I'm down to pulling the harness and picking it apart until I find a short I think? Unless anyone has a better idea. This is a six year old Terminator throttle body system on a street car with about 20K miles on it.

  2. #2
    Join Date
    Dec 2009
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    Connecticut
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    25,975

    Default

    Quote Originally Posted by doldsen83 View Post
    Would a failed/failing oxygen sensor possibly cause all my sensor readings to jump erratically?
    No, not typically.
    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

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    Sounds like major wiring issues. Andrew
    IG @projectgattago
    I do remote Holley EFI tuning.
    I deliver what EFI promises.
    Please get in touch if I can be of service.

  4. #4

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    That's what I'm hoping for, a harness is far cheaper than an ECU. Is there a diagnostic self check I can do via laptop to confirm the ECU is OK, or would I need to send it to Holley?

  5. #5
    Join Date
    Dec 2009
    Location
    Connecticut
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    25,975

    Default

    ECU diagnostic tests are performed at Holley. However, you may not have an ECU problem.

    Multiple Sensors Display Erroneous Values:
    This is sometimes a bad ground, or shorted, chaffed or burnt wiring. This may be caused by a defective sensor (since some share +5V reference and all share a common ground) or a failed actuator (IAC motor, fuel injector, etc.). Disconnect each sensor and actuator one at a time, while watching the Data Monitor (laptop "Online" with ECU). If one unplugged sensor restores the system to proper sensor values, then that's the culprit. Also, try completely disconnecting the battery for 20 minutes (or 2 hours for some severe faults), this "resets" some unusual ECU issues.
    https://forums.holley.com/showthread...ensor-Problems (Related Forum Thread - Read This!)
    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.

  6. #6

    Default

    I haven't gone much further at the moment. I Ohms tested that P1B harness and I didn't seem to find anything odd. I did break out the laptop and it cannot connect to the ECU either at this time either. The 3.5" TSLCD is saying "CAN Communication Error (1)" . To me, it's looking more like I need to give Holley a call or email about getting the ECU checked/reset. Perhaps I had an odd voltage issue that I didn't see and it corrupted the ECU firmware/software?

  7. #7

    Default

    I've reached out to Holley via the email form on the website for their guidance on the 22nd, I haven't received a response. Are they open and just backed up or are they shutdown with COVID19 things happening everywhere?

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