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Thread: Random backfire through exhaust.

  1. #1

    Default Random backfire through exhaust.

    I recently installed a 6.0L LS stock build with a Sloppy Stage 2 cam in a '78 Malibu wagon. It has a stock 4L80E and the stock 7.5 rear for now. It also has 80 lb/hr injectors Holley 151-880. Attached you will find a datalog and the tune file I'm running. Problem is randomly while driving I get a backfire through the exhaust. It does this totally random and when it happens nothing on the 3.5" TSLCD display shows anything crazy. Any help would be great. It's a Terminator X Max. Thanks again.
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  2. #2
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    Under Ignition Type, set it to Custom. Setup you Crank & Cam Sensors, and under Output Setup, change the Dwell Time to what works for your coils. You may have the Dwell Time wrong using the generic Ignition Type setting. They could be getting hot and auto firing.

  3. #3
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    Dwell Time: "3.5-5.0 msec" (← Read end of page 3 - 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.

  4. #4

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    OK, I went in and changed the settings around under Ignition. I was unsure of the settings for 24 Tooth LSx, so if someone could verify I have those correct, that would be awesome. I'll load this tomorrow morning after I get home from the firehouse. Thanks in advance. Bill
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  5. #5
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    Most, but not all, 24 tooth LS crank sensors had a single pulse cam sensor. Is the cam sensor at the to rear of the engine or the front timing cover? What coils are you using? I have Holley coils and I run 4.5 Dwell Time.

  6. #6

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    Yes, it's the single pulse type. Good catch, I just noticed the LSx option and clicked it. So I check single pulse, and if I'm correct, LSx cam sensors are Digital Rising. Not positive on that one, but I believe so. The coils are stock coils from a '03 Express Van. They're the square type.

  7. #7
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    Quote Originally Posted by onefast66nova View Post
    So I check single pulse, and if I'm correct, LSx cam sensors are Digital Rising. Not positive on that one, but I believe so.
    According to this link, yes: https://forums.holley.com/showthread...5115#post65115 (58x Crank & 1x Cam - Custom Ignition Parameters)
    (Onefast66nova, please don't type your posts like you're texting. It takes me a long time to edit it.)
    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.

  8. #8

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    OK, thank you for your help. I'll change those settings. I noticed on the link above my coils stated they needed 3.5 msec. I'll change the LSx 24 Tooth, Single Pulse Cam Sensor - Digital Rising, and report back tomorrow. Thank you to all that helped.

  9. #9

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    I changed to those settings this morning. Now the car won't start and pops through the exhaust while cranking.

    UPDATE: I changed the settings around for ignition setup. 20.0 usec Digital Falling and Dwell at 3.5. Fired up and I took it for a drive. It did pop a few times, but definitely better. I did notice the car feels like it pulls better under light acceleration with 36° of timing. Would it be safe to say to add 3° to the smaller areas, as I’m running dual knock sensors?

  10. #10
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    Quote Originally Posted by onefast66nova View Post
    I did notice the car feels like it pulls better under light acceleration with 36° of timing. Would it be safe to say to add 3° to the smaller areas, as I’m running dual knock sensors?
    That's tuning. Don't ask, try it & see if you trust your knock sensors.
    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.

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