Truck wants to die when I hit the gas

Discussion in '4.0 Engine' started by Art5, Jan 12, 2014.

  1. Art5

    Art5 New Member

    1994. pushrod 4.0. Manual 5 speed. Truck sits there and idles well. when i hit the throttle she runs like crap, acts like it wants to die. Anybody have any clue why my truck might be doing this? this is my daily driver right now so I really need to get this figured out asap. Any and all help is greatly appreciated.
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  3. kanuck15

    kanuck15 Member

    Can you come on the throttle slowly and let it build up rpm or does it not matter how fast/slow you hit the gas? Id check your fuel pressure.

    Im not great with gas engines, more of a diesel guy myself but I will help ya as best I can
  4. OP

    Art5 New Member

    Yes i can come on the throttle slowly and let it build up rpms.

    I found an injector o-ring that was leaking fuel, put a new one on, and now im having different symptoms. At idle it will miss intermittently, if i throttle up and then let go it backfires. when i hit the throttle it still runs like crap but not as bad as before. Fuel pressure test said 28 with vacuum line attached, 38 with it removed. it is a harbor freight gauge so idk how accurate it really is.
  5. kanuck15

    kanuck15 Member

    28 seems rather low. It should be 40 or so?

    As far as the miss I would look for a vacuum leak. A backfire is a dead give away of a vacuum leak. Could also be the fuel pressure issue
  6. OP

    Art5 New Member

    I just fixed the only vacuum leak I found a couple of days ago...let me check the chilton for what the fuel pressure should be...and like i said i'm not 100% confident in the accuracy of my fuel pressure gauge.
  7. OP

    Art5 New Member

    Here's what the chilton says:
    1993-1997 models
    Key on, engine off 35 to 45 psi
    At idle, vacuum hose connected 25 to 35 psi
    At idle, vacuum hose disconnected 35 to 45 psi
  8. OP

    Art5 New Member

    And here's what my test read:

    Key on, engine off 37 psi
    At idle, vacuum hose connected 28 psi
    At idle, vacuum hose disconnected 38psi
  9. OP

    Art5 New Member

    I went and bought a MAF sensor, turned the truck on, and.....big difference. I can rev it up and everything I just drove it around. if i really whomp on the throttle and let go it will still backfire but it runs and drives thanks a million to everyone who posted on here to help me.
  10. kanuck15

    kanuck15 Member

    Glad its fixed! Id still look for a vacuum leak. A back fire isnt normal and will only get worse
  11. RangerAl

    RangerAl Member

    Change out the spark plugs. These OHV are pretty discriminate when come to spark plugs. MOTORCRAFT

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