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Thread: Holley Commander 950 - Electrical Interference?

  1. #1

    Default Holley Commander 950 - Electrical Interference?

    Hello all, great source of info for EFI systems!
    I'm certainly new to aftermarket tuning and still getting to understand the system but having a problem after some re-wiring I did.

    I recently picked up a truck using a Commander 950 MPFI system. The PO had it running pretty great and worked well until I parked it to run additional circuits and power wiring into the cab and while I was under the hood I cleaned up the EFI wiring. After I was done, it started right up however the idle stared fluctuating and dipping below 500 RPM and it smelled a bit rich. While driving it and lifting my foot it would pop now and then which I thought was related to too much fuel. So I put the computer on it to see what it was doing.

    Opening the fuel map I noticed the Closed Loop Compensation creeping up to 125% as soon as the engine is warm. In addition, my A/F is 18.0 and will bump around between 16 and 18 if I change the cell values at idle but the closed loop and A/F remains the same no matter what.

    After doing some reading here and reassessing the changes I made under the hood I'm inclined to believe this behavior might be related to electrical noise or interference from grouping wiring together. However before I tear back into the harness I wanted to see if this could indeed be the cause?

    Could an O2 sensor go bad just sitting for 2 weeks? Condensation? Heat?

    Things I did:
    I re-ran the plug wires around the front of the valve covers, they basically don't cross any engine harness wires... just a sensors on the block and one or two grounds.

    I did group the injector wires with the sensors on the passenger side and the TFI module on the driver side. I also looped the wideband 02 wiring together to get it out of the way.

    On the passenger fender I ran the power wires into the cab together with the ignition box wiring (Hyfire6).

    Any ideas? Headed to Moab next week so pretty pressed to figure it out. Thanks!

  2. #2
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    I doubt you caused electrical noise interference, unless you positioned the WBO2 sensor wires very close to high voltage wiring.
    I would ensure the WBO2 sensor heats up when switching the key on and ensure you didn't inadvertently cut or damage any wiring.

    It's entirely possible that the WBO2 sensor is now in need of replacement.
    Your situation seems very similar to these threads:
    http://forums.holley.com/showthread....ning-very-rich!
    http://forums.holley.com/showthread....sue-sputtering
    See if you're experiencing the same thing - wideband O2 sensor failure.
    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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    I'm going to test the O2 sensor here today. Would be a shame if it was already failed as my rig has less than 800 miles on it and everything was new... albeit the PO took 6 years to build it

    I did notice the voltage of the O2 sensor was in the 2-2.5V range after warm up in the Fuel Map window...seems out of range as I understand the sensors should be 1V, however, not sure what is supposed to be properly displayed there...

  4. #4
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    Do you have a wideband O2 sensor or a narrowband O2 sensor?
    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

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    Quote Originally Posted by Danny Cabral View Post
    Do you have a wideband O2 sensor or a narrowband O2 sensor?
    Wideband...and I would assume the next question will be is it a Holley wideband or something else.
    EDIT: It's the Holley wideband with Bosch sensor.

    I did go out and was about to pull the O2 sensor to test when I noticed a 4 prong connector right above it and pull on it...came out...so I made sure that was connected then started it up to see if it made a difference (didn't look where it went - still getting to know the truck) I loaded the old tune - the one before I started changing the Fuel Map and known good one and it seemed to idle OK until it got warm...then started to bounce a bit and O2 Compensation started to move toward 125% - HOWEVER when I started changing the cell values at idle I did see the compensation change toward the center mark. I took some screen shots as warm up occurred...








    I turned off wideband O2 once engine was up to temp as well...no real change in idle...

    Last edited by landshark99; 04-22-2013 at 02:15 PM.

  6. #6
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    Did you read the links in my above post #2?
    If the Fuel Map is well tuned, you can operate the EFI in Open Loop (in Engine Parameters) and the engine should run fine.
    This will also prove if the wideband O2 sensor is defective, and will allow you to run the engine until a replacement sensor arrives.
    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

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    Quote Originally Posted by Danny Cabral View Post
    Did you read the links in my above post #2?
    If the Fuel Map is well tuned, you can operate the EFI in Open Loop (in Engine Parameters) and the engine should run fine.
    This will also prove if the wideband O2 sensor is defective, and will allow you to run the engine until a replacement sensor arrives.
    Yup I did, will be testing more here shortly...snowing again here and a bit cold out there

  8. #8

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    Danny -
    OK, I ran the truck in Open Loop through the Engine Parameters dialog window and there was no change.

    I saw that the Closed Loop was moving around - where before I found the loose connection it was locked at 125% so I blipped the throttle and all of a sudden the A/F and Closed Loop Compensation went from 120% to 100%...then settled in to 90-100%, where it was before. However highlighted cell values are higher in the Y axis (MAP 45 -50) in the Fuel Map from what I remember. Is this because of an increase (or decrease) in current air pressure? Also I'm at 5600FT...truck came from 7500FT where the PO lived.

    I changed a few values in the map to target the 95-100% compensation... and it seems to be staying. I turned the truck off and on and idles fine... a bit lopey but this is a 406 with an aftermarket cam in a small truck - to be expected

    Anyway I guess being a bonehead and having had a loose connection near the O2 sensor might have been the culprit but I will keep an eye on things this week and do a few datalogs to fine tune this thing even more.

    I will have more tuning questions as I know there is allot of hidden power in this 406 to unleash. Thanks for the help.

    Click image for larger version. 

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  9. #9
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    Quote Originally Posted by landshark99 View Post
    OK, I ran the truck in Open Loop through the Engine Parameters dialog window and there was no change.
    Well, I hope you didn't run it in Open Loop with a corrupted Fuel Map (from faulty WBO2 sensor/wiring).

    However highlighted cell values are higher in the Y axis (MAP 45 -50) in the Fuel Map from what I remember. Is this because of an increase (or decrease) in current air pressure? Also I'm at 5600FT...truck came from 7500FT where the PO lived.
    Yes, elevation changes will affect the MAP kPa reading.

    Anyway I guess being a bonehead and having had a loose connection near the O2 sensor might have been the culprit...
    Yes, solid EFI wiring is very important. It's a common cause for EFI 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

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    Quote Originally Posted by Danny Cabral View Post
    Well, I hope you didn't run it in Open Loop with a corrupted Fuel Map (from faulty WBO2 sensor/wiring).
    Well I loaded the last known good profile before I went to Open Loop - I saved the profile before I did any work on the wiring and before I was having any problems. That should be OK correct?

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