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Thread: Air/Fuel Ratio Rising To 35% - Closed Loop Compensation 100%

  1. #1

    Default Air/Fuel Ratio Rising To 35% - Closed Loop Compensation 100%

    I've been driving around the last couple of weeks (60-70° temps) and the Sniper has been performing well. This morning I started the truck at ambient outdoor temp, which was probably in the low 40s. I drove it a few blocks and it ran fine. I came out a few hours later to leave and the truck wouldn't stay running. I noticed my A/F Ratio started at normal parameters at startup, but started climbing sporadically up to 35%, and my CL Comp % was at 100%. The idle would smooth out and A/F Ratio would drop back to normal when the CL Comp% dropped to 98%, but that was only for a second or two before CL Comp % went back to 100%, A/F Ratio climbed and the truck died.

    I do not believe the Sniper has Learned all it needs to in the short amount of time I've driven it. How do I adjust the CL Comp % so my truck will run?

  2. #2


    I found another thread with the same problem ( I tried reflashing & disabling Closed Loop, but the truck still would not stay running. It started & ran fine for a few seconds, but the A/F Ratio would climb to 35% and die just like before. Could a bad WBO2 sensor do this, even with a fresh startup Wizard flash and Closed Loop disabled? Danny, please help. Do you have any ideas?

  3. #3


    Sounds like a WBO2 sensor gone bad to me. But Danny is the master for these types of questions.

  4. #4
    Join Date
    Dec 2009


    Quote Originally Posted by 2B32 View Post
    Could a bad WBO2 sensor do this, even with a fresh startup Wizard flash and Closed Loop disabled?
    Yes, because the ECU can't self-tune/Learn a fresh Base Fuel Table in Open Loop (no WBO2 sensor). Replace the WBO2 sensor.
    Also, you can't just replace the WBO2 sensor, and restart the engine. You must upload the last "known to be good" Global Folder,
    upload the base calibration, or at the very least, clear the Learn Table of the corrupted values from the defective WBO2 sensor. (WBO2 Sensor Information - Read 4th & 5th paragraph under "Wideband O2 Sensor Notes".)
    May God's grace bless you in the Lord Jesus Christ.

    '78 BRONCO: 508" stroker, TFS heads, 11:1 comp ratio, Dominator MPFI & DIS, cold air induction, Spal dual 12" fans/aluminum radiator, dual 3" exhaust/Magnaflow mufflers, Moroso vacuum pump, Accusump, engine oil & trans fluid coolers, 100HP progressive dry direct-port NOS, A/C, LenTech Strip Terminator wide-ratio AOD/2500 RPM converter, 3:1 Atlas II, modified Dana 44/60-lockers-4.10s, hydroboost/4-disc brakes, ram-assist/heim joint steering, Cage long radius arms, traction bars, 4" Skyjacker lift, 35" mud tires

  5. #5


    Have you actually checked it? What I do is video the issue, so I can look at it to see better what it's doing. You can also datalog it. Then go in & see what you have going on. Jimmy

  6. #6


    I called Holley yesterday and the tech I spoke to didn't seem to think the issue was with my WBO2 sensor since my A/F Ratio reading bounces around, and does not stay pegged at 35%. My fuel cell was low, so I put some more gas in thinking maybe the pickup was sucking air, but that didn't help either. The tech I spoke to suggested I increase my Coolant Temperature Enrichment from 108.5% to around 110% and my After Start Enrichment from 100% to 102%. All of this is on a fresh flash, and the problem gets worse if I press the gas. I'm going to get a datalog this afternoon to see if it gives any info on what's going on. I've also ordered a fuel pressure gauge to make sure I'm getting enough pressure to the unit.

  7. #7

    Default HELP! Low Fuel Pressure

    Last week my truck suddenly lost fuel pressure; it starts, but idles rough & dies when the throttle is pressed. I bought an in-line fuel pressure gauge which reads 60 psi during the prime cycle, but falls to 20 psi when the truck starts, then falls to 5 psi while the truck runs. I replaced the pump, but still have the same problem. This is a completely new Sniper Master Kit and an RCI aluminum fuel cell. This was a sudden issue. I had been driving it with no issues for a couple of weeks. It drove fine, I parked it, then a few hours later it wouldn't stay running. In this video, I clamped the return line to see if the regulator had failed. I was told if the pressure returned to normal with the line clamped it was a bad regulator, but if the problem remained with the return line clamped, it was a bad pump. A new pump didn't change anything, so I don't know where to go from here.

  8. #8


    If you clamp the return line it should dead head the pump, most are 90-110 psi, it shouldn't return to "normal 58-61 psi" because the fuel has no where to go. Did you replace the hose between the pump and top of the module? I've seen that hose split and will bleed off fuel back into the tank. Have you checked for any electrical problems?

  9. #9


    I'd be looking at fuel pickup & filters if it was mine.

  10. Default

    I'd look towards possibly a fuel regulator that got stuck open, it can happen and will cause low pressure.

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