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Thread: Misfire Issue

  1. #1
    Join Date
    Oct 2015
    Location
    Gonzales, LA
    Posts
    17

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    Hi Guys. I've been trying to solve a misfire issue with my car for an embarrassingly long amount of time (like 3 years, I get frustrated and it sits for like 3 months). Basically what's happening is there is a light misfire on a free rev & cruise at around 2K, then if I free rev slow up to 4K it will break up almost like it's on a 2-Step at around 3K to 3.5K. It does this while driving as well. On the datalog below, I ran it part throttle up to around 4K or so, then shifted to 3rd and just held it steady. You can see where the AFR will not come down to the target and just stays steady at 14.2. Then you will see the Closed Loop max out at 100% and the Learn goes over 20%. I went WOT yesterday and it maxed my FP compensation out at 30% and Closed Loop & Learn maxed out along with my injector duty cycle. This is an N/A 408W on E85, might make 600 HP and it runs 60 lb/hr injectors with a 340 LPH fuel pump. I run an IW crank trigger with a Holley Hall-Effect crank sensor and a Price Motorsport cam sensor. For coils, I run brand new LS heat sink coil packs and FireCore50 wires. I've verified timing is actually synced up and that the firing order is correct. Coil Dwell is set to 3 ms. I hope I'm just an idiot and there's something simple I'm overlooking.

    I've purchased an NTK wideband O2 sensor, it will be in and installed this weekend. Just trying to rule that out. Can anyone see anything on the datalog that sticks out as an issue? I also attached a System Log to see if my cam & crank signals look OK. I hope the Dropbox link works. Thanks! https://www.dropbox.com/sh/vbxnm1g5d...CcMKr64ka?dl=0

    UPDATE: I also noticed my wideband won't drop below 14.1 in various situation's and there is a red dot next to AFR left that says "uncal!". I'm sure that's not right. Hoping that new NTK WBO2 sensor will help.

  2. #2

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    It could be WBO2 sensor is starting to fail. But every time I had mine fail it would show 35:1 AFR and make engine run pig rich. Could be wiring issue in WBO2 harness or corrupted firmware install.

  3. #3
    Join Date
    Dec 2009
    Location
    Connecticut
    Posts
    22,979

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    I'd replace the WBO2 sensor, but there's a WBO2 sensor testing procedure at end of "Wideband O2 Sensor Notes": http://forums.holley.com/showthread....ension-Harness (WBO2 Sensor Information)
    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.

  4. #4
    Join Date
    Nov 2014
    Location
    Ont. Canada
    Posts
    1,431

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    I'd say there's something wrong with your WBO2 sensor. The Closed Loop keeps adding fuel, but the AFR does not drop. So it over fuels the engine. You could reduce your Closed Loop Limits.
    Last edited by 81 TransAm; 08-21-2019 at 06:44 AM.

  5. #5
    Join Date
    Oct 2015
    Location
    Gonzales, LA
    Posts
    17

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    Thanks guys. I'll change the WBO2 this weekend and report back.

    UPDATE: I had some time today and took the sensor out. I'm using an O2 heat sink and I see moisture inside of it when I took the sensor out. The sensor is at the 11 o'clock position, so I thought I would've avoided this, but maybe I should try this without the heat sink? Have you guys had any issues with moisture in the heat sinks?

  6. #6
    Join Date
    Dec 2009
    Location
    Connecticut
    Posts
    22,979

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    Which WBO2 sensor heat sink are you using? Innovate Motorsports HBX-1 Heat-Sink Bung Extender?
    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
    Join Date
    Oct 2015
    Location
    Gonzales, LA
    Posts
    17

    Default

    Yes, that's the one.

    UPDATE: I installed the new sensor and it works now. The AFR actually fluctuates with fuel being added. I can't take it for a drive tonight, but I'll drive it first thing Saturday morning and report back if the misfire is still present or not. It appears the fueling in that 3-4K range was super rich, and when I took some fuel out it seemed to clean it up quite a bit.

    UPDATE 2: I got to drive the car today and it's all fixed I think! It pulled 15-30% throughout the fuel table and it smoothed out a lot. WBO2 was definitely the issue.Im guessing the moisture on the old O2 and in the heat sink didn't help.
    Last edited by 95gts5oh; 08-24-2019 at 09:08 PM.

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