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Chevy truck missing at high speed

Discussion in 'GM Powertrain' started by Dons31a, Dec 11, 2010.

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  1. Dons31a

    Dons31a New Member

    I have a 1994 chevy p/u silverado with a 5.7 engine. It has 306,800 miles on it. Recently at high speeds above 70 the truck will miss like a plug wire, fuel injectors, or an electrical problem. How do you check for codes. I know you can jump A and B on the diagnostic plug. There are no letters on the plug to show A and B. Does anyone know which pins they are? I replaced plugs about 3 months ago. I need help because I have a long drive on Monday.
  2. murdog94

    murdog94 Epic Member 5+ Years 5000 Posts

    WEll there are a few threads that show you where they are located

    I do wonder when was the last time that you did a tune up (cap, rotor, wires and a fuel filter?) Also check the PCV valve
    obviously check the codes first but those are things to think about as well.
  3. Dons31a

    Dons31a New Member

    Thanks for the info. I replaced cap, rotor, and wires about 4 years ago The filter was changed about 5 years ago. I don't know about the pcv valve. I do keep up my maintenance on my truck as you can see with the mileage. I have had it since new and have never sent it to a mechanic. I ask a lot of questions and finally figure out where the problem is. This is the first time to using a forum. Thanks to all for the help.
  4. murdog94

    murdog94 Epic Member 5+ Years 5000 Posts

    i would take a close look at the cap and rotor, since most of us have to change them yearly to every other year since they corrode quite quickly. So after you get the codes i would look at that as well since more than 2 years and you are likely to have problems with the cap, and rotor. which will cause a miss very easly....
  5. Dons31a

    Dons31a New Member

    You might be right about the cap, because when I did replace it, I had to break it up for being so corroded. I have only changed it once since I have had the truck. Will this cause a high speed miss? If it does, I sure would never of thought of that. I would think it would miss all the time. Thanks for all your help. I knew I would get a direction to follow on this forum.
  6. murdog94

    murdog94 Epic Member 5+ Years 5000 Posts

    Yeah i would definately just replace the cap then. and yes a high speed miss makes sense because you have more RPMS than at idle and the speed of the rotor will have less time in contact therefore less time for the spark to get thru.. as i mentioned that is a very common thing with these trucks and since most of the older trucks didnt have this problem or they got changed more thanks to points it gets overlooked quite easly..
    Also the parts are just plain old cheap, so they dont last as long.
  7. Dons31a

    Dons31a New Member

    I believe you about cheap parts. I will replace the rotor and cap tomorrow and take it out on the road above 70 and check out the problem. I knew I could find someone on here to lead me in the right direction. Thanks a million. I will also check the code to be sure.

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