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Thread: New problem with 99 Lightning engine running rough

  1. #1
    Registered User
    Name: Bob


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    New problem with 99 Lightning engine running rough

    I have a 99 lightning with 81K. I have had the truck for about 10 years and purchased it with only 36K on the odometer. With the exception of a faulty coil pack a couple of years back, the truck has run perfectly. It has always started almost instantly to the point of where you just turn the key to start and then back to run almost immediately. I noticed over the last several months that it took a little longer to actually start to run....just literally a second longer, if that. Out of habit, my normal routine was to just turn the key back to run almost immediately after turning it to start. But recently when I did this, the truck would run rough for a second or two then smooth out. A couple of days back, I went to start the truck and once again turned the key back to run before the engine was completely running. This time it didn't smooth out as it has in the past and stalled. It almost sounded as if it was choking out. The truck is now difficult to start at all, and won't stay running. Upon removing the air breather (an AIRAID filter similar to K&N which was on the truck when I purchased it) the engine ran a little smoother but still did not run to power. I unplugged the mass air flow circuit and between that and the filter the engine would idle smooth and then rough again. No check engine or service light appeared on the dash and we ran a scan to look for codes. Initially PO102 and P0602 as well as P1000 came up, however I am not sure if those came up because I previously disconnected the MAS or not. I was going to try a new MAS but before purchasing that, does anyone have any ideas as to what this problem might be? Thanks folks
    Bob

  2. #2
    refreshed and alive again
    Name: Don

    SA94Lightning's Avatar
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    Fuel pressure all good?
    Maybe low pressure at start up.




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  3. #3
    Bone idle and work shy!
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    fishin-nole's Avatar
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    Fuel filter clogged or fuel line dropped off or the plastic Y is cracked.


    Just another slow truck.

  4. #4
    Registered User
    Name: Bob


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    Thanks....I have a feeling it might be a fuel problem as I ran it very low and just got $15 bucks worth. Trying to drain it and cant get a siphon in the tube.

  5. #5
    Bone idle and work shy!
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    I droppped mine with 3/4 tank. Alone in the garage on the ground.


    Just another slow truck.

  6. #6
    Name: Bruce

    Boss Hoss's Avatar
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    Check all filters as well as vacuum lines. Is your idle air control clean?

  7. #7
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    Quote Originally Posted by Stpete View Post
    Thanks....I have a feeling it might be a fuel problem as I ran it very low and just got $15 bucks worth. Trying to drain it and cant get a siphon in the tube.

    I think there may be a screen down in the fuel fill pipe, mainly to prevent others from siphoning your fuel. There is a plastic Y in the fuel tank that connects the two pumps together. They are known to break. There is a metal one available that is much better. Also, have you ever replaced or deleted the elbow on the back of the motor, that connects to a T fitting in the PCV system on the passenger side? They are known trouble makers as well. But typically it throws the two lean codes when bad, P0171/174. Usually a roguh idle is caused by a vacuum leak somewhere.
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  8. #8
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    Try running a bottle of Chevron Techron Fuel System Cleaner through. Let the fuel level get low, put in a 12 ounce bottle of Techron, drive until the low fuel light come on and then fill. Works for me every time. Do this just before you change the engine oil to get the contaminates out.
    1999 Black #1212 (gone) now 2003 Black #1714

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