Random misfires & loss of fuel pressure!! Help...
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Northstar Engines and System Technical Discussion Discussion, Random misfires & loss of fuel pressure!! Help... in Cadillac Engine Technical Discussion; 98 deville runs rough, loses fuel pressure. Then i turn off and back on and its temporarily restored. Codes pcm ...
  1. #1
    laclover216 is offline Cadillac Owners Member
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    Random misfires & loss of fuel pressure!! Help...

    98 deville runs rough, loses fuel pressure. Then i turn off and back on and its temporarily restored. Codes pcm 0171, 0174, 0151, & 0300 randomly sets the mil. I clear the light each time and they keep coming back. All, or one. Both mufflers broke so i understand that this could be a cause or contributor to the problem. If the car runs idle for minutes a smell of emissions enters the interior from the dash vents. Could all this actually be a leaky manifold gasket, plentinum, vac line, or stuck egr??

    O2's are believed to be shot now but not sure. I did get a code once that a bank 1 sensor had low voltage but it has yet to com back since cleared. Before the mufflers broke emissions was fine, unscented and clear to pass emissins testing. Cat is not bad. No eggish scents. What is the problem? New spark plugs, was going to replace the coil pack with the one from my old 97 that was fine. But im not sure. Could also be the problem though. I am going to replace the mufflers this week but what else. If i put the mufflers on i doubt if it clears the problem completely. The interior smell could also be coming from the heavy emissions seeping from the rear pipe when the car is sitting still for a short period. But only when i put the car in gear or turn the hvac on. Please help.

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    Ranger's Avatar
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    Re: Random misfires & loss of fuel pressure!! Help...

    98 deville runs rough, loses fuel pressure.
    Sounds like a bad fuel pump. What was the fuel pressure?

  4. #3
    laclover216 is offline Cadillac Owners Member
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    Re: Random misfires & loss of fuel pressure!! Help...

    woow. i just got the fuel pump put on where i bought the car and it started humming again a week later. i need to go back tomorrow and have them check it out. it was humming before it went out the first time. so maybe they gave me a defected one or something else is causing it to go bad so quick that they overlooked. i paid $400 plus for the whole modular assembly.

  5. #4
    laclover216 is offline Cadillac Owners Member
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    Re: Random misfires & loss of fuel pressure!! Help...

    maybe they forgot to change filter or is that included in assembly?

  6. #5
    Ranger's Avatar
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    Re: Random misfires & loss of fuel pressure!! Help...

    The filter is separate.

    If the pump is new that's not likely the problem. Have you checked the fuel pressure? I said bad pump because you said "It looses fuel pressure".

  7. #6
    laclover216 is offline Cadillac Owners Member
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    Re: Random misfires & loss of fuel pressure!! Help...

    No i havent checked the pressure but this pump is whining loud as hell just like the last one started till it went out. And when i turn the car off then right back on i temporarily have better pressure. Im lost....

  8. #7
    laclover216 is offline Cadillac Owners Member
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    Re: Random misfires & loss of fuel pressure!! Help...

    however when the car is in park i can rev it up or it idles with no problem even in drive on the brake. i'll get the fuel pressure checked tomorrow.

  9. #8
    Ranger's Avatar
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    Re: Random misfires & loss of fuel pressure!! Help...

    If you paid $400 to have a fuel pump installed and it is whining, I'd take it back and have them check it out.

  10. #9
    laclover216 is offline Cadillac Owners Member
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    Re: Random misfires & loss of fuel pressure!! Help...

    will do first thing tomorrow. thank you very much. im interested to know the connection so i'll post you.

  11. #10
    hardley-etc is offline Cadillac Owners Fanatic
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    Re: Random misfires & loss of fuel pressure!! Help...

    spend the extra 20.oo or so and get the wiring harness changed too
    you did right?

    if its not put in exactly straight could has chaffed a wire on the harness, that is making intermittent contact with a ground

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