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Truck misses at all speeds ~ 1998 Chevy

Discussion in 'Chevy C/K Truck Forum' started by Davidh, Mar 21, 2013.

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  1. Davidh

    Davidh New Member

    Have a 1998 1/2 ton with a 5.0 2 wheel drive. Great truck runs well when running properly. Idles great takes off well bu about 20 mph and above it will miss badly. My mechanic though it might be the distributor. I replaced with a new one . It did not make a difference. He stated that the popping sound I heard was a lean pop which could indicate a bad fuel pump. Haven't tried that yet. I was wondering if it might be a emission component that could cause the problem. I plan on using some Seafoam in the vacuum system to clean them out. does any one have an opinion.
  2. geo1

    geo1 Member 1 Year 100 Posts

    e.g.r?try disconnecting it from vac.supply,plug vac.supply,test drive
  3. Pikey

    Pikey Moderator Staff Member 2 Years ROTM Winner 1000 Posts

    I would check the fuel pressure with a gauge. I also wonder if your egr valve is stuck.
  4. Crispyt

    Crispyt Rockstar 100 Posts

    I had the same exact problem awhile back with my truck, it just turned out that it was a plugged fuel filter. But the first thing I would do is do a fuel pressure test on the system first. Make sure your getting the correct fuel pressure at the fuel rail. Always trouble shoot like this.... Fuel------> Ignition------> Compression...


    Its possible that your ignition coil is worn out and under a load or higher RPMs it can't keep up with the demand. If you were to keep your truck in park or neutral and bring the RPMs up does it start to miss or only under a load?


    If it seems like it's idling normally then my guess is it's probably not a vac leak, that will usually cause a higher idle or it will die out a lot. Make sure that none of your plug wires are burned or bad. Try starting it at night when its dark and pop your hood open and see if you can see any of the wires arching out.

    Also it could just be something as simple as needing a tune up.. Plugs, wires, air and fuel filter, etc...

    Hope this helps a little, good luck!
  5. Davidh

    Davidh New Member

    thanks for the reply. I will check all those things. Replacing the fuel pump will be my last resort
  6. Davidh

    Davidh New Member

    Replaced the fuel filter and the coil. Improved the missing out somewhat. still doing it. I rented a fuel pressure gauge form the local parts place and it was broken. Waiting for them to get a new one to borrow so that i can check the pressure. The instructions say to test the pressure at the fuel filter. Does anyone have any other way to test?
  7. geo1

    geo1 Member 1 Year 100 Posts

    best place?as long as you are in front of the fuel pressure regulator,did you try e.g.r. disconnect?
  8. MrShorty

    MrShorty Epic Member Staff Member 5+ Years 1000 Posts

    I know different cars are designed differently. Ford and GM's have a "Schrader valve" (looks like a tire stem) in the fuel supply line/on the fuel rail that is intended specifically for testing fuel pressure. On my '98, it is on the supply line kind of between the engine and the firewall. Assuming the pressure tester you are renting is built with this valve in mind, that is the easiest place to test fuel pressure.

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