Thread: high idle with a random misfire

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  1. #1 high idle with a random misfire 
    Regal GS Level Member BoostedPontiac's Avatar
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    I would like to see what could be causing her to idle high. It idles around 1200 to 1400? She will also randomly misfire every once in a while. What could cause this?
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  2. #2 Re: high idle with a random misfire 
    GTP Level Member tomtom123's Avatar
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    I'm sure someone more experienced can and will chime in, but mass air flow, throttle position sensor, vacuum leak. Could probably use a tune up if you haven't already done plugs and wires

    Sent from my SM-N900P using Tapatalk
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  3. #3 Re: high idle with a random misfire 
    GT Level Member lewis1952's Avatar
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    I had the same problem. Try this. Turn the key on and press the gas pedal to the floor hold it for 3 sec, let off, pump it to the floor 5 times in 7 sec let off Turn key off then start it . See if this fixes the high idle. If not follow Toms suggestions.
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  4. #4 Re: high idle with a random misfire 
    Turbo is the way to go. Fivefingerdeathpunch's Avatar
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    More info is really needed. You wouldnt go to a shop and say what you said, because they'd just look at you with a dumb look because they have no idea what you are talking about and what you drive.


    What do you drive?

    Any recent repairs/maintence done?

    Modded or stock?

    What else do we need to know about the vehicle to help?

    What have you tried?

    SMGPFC Member #1
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  5. #5 Re: high idle with a random misfire 
    Regal GS Level Member BoostedPontiac's Avatar
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    I drive a 1999 Grand Prix with a cammed L67. I bought plugs, wires, oil, and an oil filter but need a day off to install. The car is mildly modded. I havent tried anything tofix the issue because it happened on my way to work today.
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  6. #6 Re: high idle with a random misfire 
    Turbo is the way to go. REDCRAPGP's Avatar
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    What cam is in it?
    Squirrels are my engine. I need a Ford Regal
    04 Comp G.
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  7. #7 Re: high idle with a random misfire 
    Regal GS Level Member BoostedPontiac's Avatar
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    NIC cam
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  8. #8 Re: high idle with a random misfire 
    Regal GS Level Member BoostedPontiac's Avatar
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    Quote Originally Posted by lewis1952 View Post
    I had the same problem. Try this. Turn the key on and press the gas pedal to the floor hold it for 3 sec, let off, pump it to the floor 5 times in 7 sec let off Turn key off then start it . See if this fixes the high idle. If not follow Toms suggestions.
    Is that some kind of idle re-learn?
    98' GP coupe NIC Pacesetters, E85, FSIC, 2.6, heads, blah
    11.82 @ 118.4 with a 1.8 60ft
    Retired: 99' Regal GS Turbo 11.428 @ 122.61 1.7 60ft.
    Retired: 99 GTP top swap nic setup. 13.37@106
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  9. #9 Re: high idle with a random misfire 
    GT Level Member lewis1952's Avatar
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    yes it fixed my high idle problem
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  10. #10 Re: high idle with a random misfire 
    Turbo is the way to go. Fivefingerdeathpunch's Avatar
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    With a NIC cam, the code P0300 needs to be shut off.

    But I think you need to start with swapping those parts and looking for a vacuum leak. I'd hope you have some sort of scan gauge or whatever to help montior what the car is doing.

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  11. #11 Re: high idle with a random misfire 
    GXP Level Member Timing's Avatar
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    How do you know its misfiring? Is there a code or are you scanning for misfires?
    08 MazdaSpeed 3- Treadstone tr8l, Ebay Piping, Ported intake,Thermal gasket, Cs Injector Seals,Cobb intake/inlet, Autotech Internals, Poly mounts, Speed Daddy DP, Magnaflow CB,
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  12. #12 Re: high idle with a random misfire 
    Regal GS Level Member BoostedPontiac's Avatar
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    The code was P0300
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  13. #13 Re: high idle with a random misfire 
    Turbo is the way to go. REDCRAPGP's Avatar
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    P0300 needs to be turned off for most cams
    Squirrels are my engine. I need a Ford Regal
    04 Comp G.
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  14. #14 Re: high idle with a random misfire 
    Regal GS Level Member BoostedPontiac's Avatar
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    I also found out I need a new tps. Would low fluid in the trans make is shift horrible. I thought my pcs was going out but I found my trans dipstick was very loose.
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  15. #15 Re: high idle with a random misfire 
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    Yes low fluid will cause shift issuez
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  16. #16 Re: high idle with a random misfire 
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    Also what does the rpms drop to in gear?
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  17. #17 Re: high idle with a random misfire 
    Turbo is the way to go. BillBoost37's Avatar
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    With that cam, was any programming down to the pcm?

    I've seen idle be vacuum leak, throttle/cruise cables bound/out of place on strut tower, TPS, tuning
    I drink..so consider that when reading my posts.

    2010 Audi A6 Dual IC's
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  18. #18 Re: high idle with a random misfire 
    Regal GS Level Member BoostedPontiac's Avatar
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    It was my TPS. When it was tuned, they didn't remove the misfire code.
    98' GP coupe NIC Pacesetters, E85, FSIC, 2.6, heads, blah
    11.82 @ 118.4 with a 1.8 60ft
    Retired: 99' Regal GS Turbo 11.428 @ 122.61 1.7 60ft.
    Retired: 99 GTP top swap nic setup. 13.37@106
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