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Thread: Miss at high RPM in 2nd

  1. #1
    Garrett booster
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    Miss at high RPM in 2nd

    Having some issues with a miss @WOT in 2nd gear at high rpm (4000+)

    The odd part is that it does not miss out @ WOT in 3rd. In 3rd The engine tops out at about 5300 RPM going into the corners before I have to brake but I don't get the miss that I get in 2nd.

    Everything from the coil to the plugs is brand new

    I have checked fuel pressure, map voltage, coolant and air charge voltages and they all seem ok. Air charge voltage was a bit off at 3.1V but everything else was about what the charts call for on voltages. Don't think the air charge sensor being a little high would cause a bad miss tho.

    The one and only thing that I found that seemed wrong on the car was the knock sensor being a half turn loose. I could see it rattling and causing timing to be pulled but I wouldn't think this would cause a miss. If it where a street car I could just drive it and see but unfortunately I can't do that and the next race I will be driving it in is a 200 Lap race and I really don't want to be working out issues with the cars driveablity during that race.

    Please anything else you guys can think of for me to look at post up. Thanks for any help

    Car is a 2.5 N/A High Compression engine with a Turbo Intake/Injectors, and Runs off a Logic Module Computer Set Up

  2. #2
    Moderator Turbo Mopar Staff Force Fed Mopar's Avatar
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    Re: Miss at high RPM in 2nd

    Might be a timing issue. Next time you run it, check the vacuum reading at the misfire occurrence.
    Rob M.
    '89 Turbo GTC

    2.5 TIII stroker, 568 w/ OBX and 3.77 FD

  3. #3
    Garrett booster
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    Re: Miss at high RPM in 2nd

    Are you thinking cam timing or spark timing? I'm assuming either way im looking for the needle bouncing all over due to ignition while the intake valve is open?

  4. #4
    Moderator Turbo Mopar Staff Force Fed Mopar's Avatar
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    Re: Miss at high RPM in 2nd

    ignition timing. Log the knock sensor and see if it's showing anything when it happens.
    Rob M.
    '89 Turbo GTC

    2.5 TIII stroker, 568 w/ OBX and 3.77 FD

  5. #5
    Hybrid booster
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    Re: Miss at high RPM in 2nd

    I had a very similar issue that turned out to be the ground at the fuel rail.
    Engine would miss / cough / sputter in 2nd around 3000 RPM, would be less in 3rd but wouldn't miss in 4th or 5th. It seemed to be a combination of load and vibration.

  6. #6
    Boost, it's what's for dinner... Turbo Mopar Staff Aries_Turbo's Avatar
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    Re: Miss at high RPM in 2nd

    whats the AFR at the miss zone?

    wideband on the car?

    Quote Originally Posted by turbovanman
    This one is easy, I have myself to blame, I rush things, don't pay attention to gauges when I should, change to much stuff at once then expect miracles, the list is endless.

  7. #7
    turbo addict
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    Re: Miss at high RPM in 2nd

    if the coil is on the inner fender and you still have the long coil wire check the terminal on the coil wire is tight in the socket in the top of the coil

    my shelby z used to stumble - it took awhile to find that lose connection
    it would only happen when the car went forwards with enough force to cause the coil wire to move
    - like dureing a hard second gear pull

    .. wiggle it while the car is running

    I should add be carefull not to zap yourself trying
    Last edited by Dr. Johny Dodge; 09-16-2017 at 01:25 PM.

  8. #8
    turbo addict
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    Re: Miss at high RPM in 2nd

    What spark plug gap?

  9. #9
    Garrett booster
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    Re: Miss at high RPM in 2nd

    Coil is where the washer bottle normally mounts and i switched to the newer style coils because i can change it over to another one in 5 seconds since the connector clips on. I sanded the ground on the fuel rail this spring when I was putting the car together but sanded it again just to ensure a good connection. I dont have a wideband, just and AFR gauge which is always running lean at WOT. I changed my tune to a 13.5:1 AFR to hopefully help with this.

    I also found that my fuel pump had low voltage due to a worn switch so I put a new one on and the pump is getting full voltage and sounds like it is running faster now. I don't have any higher fuel pressure but I assume that under WOT at close to Redline RPM's a slow running pump could cause lower fuel pressure which could have been causing my misfire

    I run the plug gap at .40 or .45 Normally .45 seems to give a bit more power but in longer races i run .40 to keep stress down on the coil
    Last edited by enduro74; 10-31-2017 at 06:45 PM.

  10. #10
    turbo addict
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    Re: Miss at high RPM in 2nd

    I was having a miss after 5300 in my PT cruiser GT, stock at the time...new plugs and wires...premium gas. Octane booster worked for me...I was shocked at such a simple fix, since I AM NOT a wrench by any means.
    [SIZE=3][COLOR=#000000]47 Time NHRA/IHRA drag race champ-----84 Plymouth Horizon/1 of 84 HO equipped from the factory/1910 lbs, 2.5 with carb, nearly 315,000 miles-----04 SRT4/S2 with S3 turbo/12.17 @ 119/DOTs/93 Octane/SOLD-----2003 PT Cruiser GT, won a True Street class at the 2017 National Muscle Car Association World Street Finals-----2010 Toyota Prius/my delivery truck, 77.9 mpg best and NOT A PLUG IN, nearly 230,000 miles and way over 5600 miles per month! [/COLOR][/SIZE]

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