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Thread: MAP lazy/incorrect?

  1. #1

    Default MAP lazy/incorrect?

    OK, finishing up my second LS/turbo Holley build and I have some weird stuff going on. Specs are 5.3L cam/springs 7875 turbo 80 lb/hr Deka knock-offs. Anyway, upon 1st start I did a firmware update (went perfectly), took my known good tune from my other car. I changed to 5.3L and a few minor things to base tune. Did all 1st start procedures with zero issues. Started it and it ran like total crap. Was loading up, way rich, etc. I could only keep it running 20-30 seconds at a time. Started monitoring all sensors and found MAP maxed out on 3.5 bar at 352 kPa at idle, hence commanding to 10° of timing and 10:1 AFR. It was an AEM 3.5 bar MAP sensor. So after some searching, I found the AEM MAP sensor would need to be calibrated to HP. I decided to forgo that and bought the Holley 3.5 SS MAP sensor. Now with that sensor installed, it reads 274 kPa when I turn the key on not running, after about 45 seconds to a minute kPa starts dropping slowly to 104 kPa (takes about 2-3 min). If I try to start it still won't go below 104 kPa and if I key it off and back on it goes back to 274 kPa. So I called Holley tech line this afternoon they told me to unplug all sensors, and verify 5 volts on orange MAP sensor which I did. Otherwise they said to send it back as they did have some HPs with a MAP circuit issue. So I guess it's going into the mail tomorrow. Sorry for long winded, just wondering if anyone has had this issue or any suggestions?

  2. #2
    Join Date
    Dec 2009
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    Connecticut
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    This may be caused by a defective sensor (since some share +5V reference and all share a common ground). The CTS & MAT are thermistors, they only share the Sensor Ground. Since the TPS, MAP, Fuel & Oil sensors share the same +5V & Ground, I'd disconnect each sensor one at a time (laptop "Online" with ECU), and see if one unplugged sensor rectifies the fault. If so, then that's the culprit. I'd try troubleshooting these sensors key-on/engine-off.
    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 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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    Danny, as per Holley tech line I did just that. All those sensors were reading fine (I had laptop hooked up and also monitoring with 3.5" TSLCD) as I unplugged each one it would read "error". Danny, is it possible to have a bad sensor and still have them all reading properly?

  4. #4
    Join Date
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    Connecticut
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    Quote Originally Posted by jasonsnova View Post
    Danny, is it possible to have a bad sensor and still have them all reading properly?
    Yes, it depends how the sensor fails.
    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

    Default

    So I just went out before work and did all the sensor unplug again, no change. I also unplugged them all with exception of knock sensor, at same time and no change. Still starts off at 274 kPa and slowly counts down to 103 kPa.

  6. #6
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    Dec 2009
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    Connecticut
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    Contact Holley Tech Service (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.

  7. #7

    Default

    Things not going well. I talked to Holley several times, one tech I talked to told me some ECUs had a issue with MAP circuit. I called next day and the next guy had no clue what that was about. I sent ECU in to have checked. Guy #2 called me today said they found nothing wrong and my tune looked fine. He had zero solutions or ideas why I'm getting this non functional MAP. I don't know if there is a issue in the harness? On this particular build the only spliced wire I did was the MAP sensor, and I've verified wiring several times (Holley 3.5 SS MAP sensor, orange wire to orange wire 5V power, red black to pink sensor, and black/white wire sensor ground). All power and grounds were soldered and all other sensors and functions seem to be working perfectly. I have not got the ECU back from Holley yet, so I can not verify anything yet. As much as I really don't want to I guess my next step will be to rob the ECU out of my other car and maybe the MAP sensor to compare (I really really don't want to do that). Guess I'm a bit frustrated with Holley's lack of suggestion (like zero).

  8. #8

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    Just curious if you noticed what the barometric pressure reads while it "counts down to 103 kPa".

  9. #9
    Join Date
    Dec 2009
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    Connecticut
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    I'd also try reflashing the ECU firmware, it might be corrupted. At least try completely disconnecting the battery for 20 minutes. This "resets" some unusual ECU issues.
    http://forums.holley.com/showthread....2193#post72193 (EFI Software/ECU Firmware Problems)
    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

    Default

    I believe the barometric pressure was in the 90s. I tried the disconnect. If it persists, I guess I could try to download a newer version of firmware and give that a shot.

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