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Thread: Misfires, High Idle & Whistle Noises

  1. #1

    Default Misfires, High Idle & Whistle Noises

    I have been working with Holley on my issues, but I'm not sure if someone else has seen these issues.

    High Idle Issue: The truck warms up just fine and idles correctly. It gets up to 195°F and kicks on FAN1. After about 1-2 minutes, it opens the IAC and starts to immediately idle at about 2200-2500 RPM. This only happens in park. If you put it in gear, it goes down to 800 RPM.

    Whistle Issue: When the vehicle is in park, I can rev the throttle and no noises happen. If I'm driving the vehicle, I push the throttle about 25% and I get a whistle that sounds like a belt squeal. When you come off of the throttle, it goes away. It sounds like I have a turbo. I haven't tried blocking the IAC port with tape yet. Edelbrock Performer RPM Intake and the gasket that came with the Sniper EFI kit.

    Misfire issue: I used to drive the truck about 10 miles and it would start to misfire & act up. You would hear the misfire and look at the handheld to see the AFR go to 9-10, probably cause it didn't burn that fuel. I was wondering if it was an issue with the FAN1 & FAN2 triggers. I have two fans that I hooked the relays to. The power comes from the battery to the fuse to the trigger side of the relay, then to the lead on the ECU harness. It triggers them with the stock settings. It always seems to act up when it says FAN1 on. I disconnected the ECU harness and wired them directly to a switch. I can start the vehicle and they both come on. Since they are both running, it helps keep the vehicle below 185ish. I'm able to finally drive the vehicle 30+ miles without issues in 30°F outdoor temp. The temp got up to 50°F that day and I had it start to act up at around 188+°F. I was told to adjust the Coolant Temp Enrichment, but I'm not sure what I'm looking for.
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    Last edited by jbrinkerhuff; 12-16-2017 at 12:06 AM.

  2. #2

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    Quote Originally Posted by jbrinkerhuff View Post
    Misfire issue. I used to drive the truck about 10 miles and it would start to misfire & act up. You would hear the misfire and look at the handheld to see the AFR go to 9-10, probably cause it didn't burn that fuel.
    I'm pretty sure that a misfire should cause a lean indication, because the oxygen isn't burning.

  3. #3
    Join Date
    Dec 2009
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    Connecticut
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    Quote Originally Posted by jbrinkerhuff View Post
    Misfire issue: I used to drive the truck about 10 miles and it would start to misfire & act up. You would hear the misfire and look at the handheld to see the AFR go to 9-10, probably cause it didn't burn that fuel.
    Ignition misfires cause a false lean condition, which show up as momentary full lean spikes, not rich. Remember, the WBO2 sensor is an air (oxygen) sensor, not a fuel sensor.
    Clamping a timing light on each cylinder, works well for misfire detection (watch for consistent flashing). Test drive it with a timing light taped to the windshield if you have to.
    https://forums.holley.com/showthread...2936#post62936 (Related Forum Thread)

    High Idle Issue:
    https://forums.holley.com/showthread...-Idle-Solution! (Holley Sniper EFI High Idle Thread)

    Whistle Issue:
    Research the Sniper EFI forum about installing a four hole spacer. Read post #24 HERE.

    I was told to adjust the Coolant Temp Enrichment, but I'm not sure what I'm looking for.
    http://forums.holley.com/showthread....6649#post66649 (Coolant Temperature Enrichment % Table Tuning)
    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

  4. #4

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    I took the truck to a tuner today and he verified everything is good to go. He did several pulls on the dyno after warming it up to operating temp. He adjusted the IAC and got it to idle at 1100 RPM in Park/Neutral. He was able to adjust the AFR and get it running great on a dyno including WOT pulls. I pickup the vehicle and drive about 10 miles and it starts to act up & misfire. What am I missing here, this is starting to get really expensive?

  5. #5

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    Do you have a datalog of the misfire? I just see your high idle datalog. Also, is 1100 RPM what you were after for an idle or was that all he could get it to?

  6. #6

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    I'm waiting for it to get warmer so I can drive it around. Do you know if I can drive it without the IAC hooked up? It's clearly possessed and I feel like it's not needed at all. The last test drive I was on, it started acting up after it warmed up. I was sitting behind a car that was turning left, and the IAC opens up and it idles so high, I can't hold the brakes enough. I'm forced to put it into neutral. I'm getting really close to converting back to the Holley 600 carburetor, to verify that the ignition system is not the issue with the misfires. It's a brand new HEI from Jegs. I have new plugs & wires. The entire vehicle harness has been replaced, and all grounds are good.
    Last edited by jbrinkerhuff; 02-11-2018 at 07:23 PM.

  7. #7

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    You can drive without the IAC hooked up, but there may be some issues with how it idles in & out of gear, and the transition between in & out of gear. Have you checked your advanced idle speed settings to see what idle RPM it shows for -40°F?

  8. #8
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    Quote Originally Posted by SatherCS View Post
    Have you checked your advanced idle speed settings to see what idle RPM it shows for -40°F?
    https://forums.holley.com/showthread...-Idle-Solution! (Holley Sniper EFI High Idle Thread)
    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

  9. #9

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    Yeah, it does not show the spike on the graph like the picture.

  10. #10
    Join Date
    Nov 2014
    Location
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    I once had a carb that had a whistle like you are describing at part throttle. It ended up being a vacuum leak at the base plate. Check for vacuum leaks. And I would pull the injectors to see if any of the injector seals are damaged.

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