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420A need help RS laggy acceleration, backfiring

Posted by Slow_Rs, Oct 23, 2020

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  1. Slow_Rs

    Slow_Rs Probationary Member

    10
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    Joined Oct 23, 2020
    glasgow, Kentucky
    i have a 98’ rs and i have no idea what’s wrong with it, when the car first starts and running it’s fine but does have a little delay with acceleration then when it gets hot it’s fine other from the acceleration, i turn it off then turn it back on and then it will sound cammed and it will backfire from the manifold. i’ve replaced the IAC check plugs and wires, they’re fine, the EGR got taken out and idk if that has to do with the issue at all, any help will be appreciated!
     
  2. BLACK'98DSM

    BLACK'98DSM Proven Member

    2,340
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    Hoover, Alabama
    Deleting the EGR will not make the car misfire.

    When you had the plug wires out, did you notice any oil in the spark plug tubes on the head? Sometimes the VC gasket will leak and let oil down in there causing and interruption in spark, a misfire.
     

    Road Race Build 4K  10  25

    1998 Mitsubishi Eclipse N/T
    fwd · manual · 2G DSM

    79  5

    1998 Ford Mustang GT
    rwd · manual · Misc Vehicles
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  3. Slow_Rs

    Slow_Rs Probationary Member

    10
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    Joined Oct 23, 2020
    glasgow, Kentucky
    wasn’t any oil on them, i have replaced the vc gasket, iac and the ignition coil and still no luck.
     
  4. BLACK'98DSM

    BLACK'98DSM Proven Member

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    Hoover, Alabama
    If it backfires from the intake manifold then you probably have bad timing.
     

    Road Race Build 4K  10  25

    1998 Mitsubishi Eclipse N/T
    fwd · manual · 2G DSM

    79  5

    1998 Ford Mustang GT
    rwd · manual · Misc Vehicles
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  5. Slow_Rs

    Slow_Rs Probationary Member

    10
    1
    Joined Oct 23, 2020
    glasgow, Kentucky
    timing is fine checked that and also check the injectors and they’re fine as well, pulled the fuel filter today and it was extremely clogged so i have to put that in, it it doesn’t help then i’m lost.
     
  6. BLACK'98DSM

    BLACK'98DSM Proven Member

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    Hoover, Alabama
    This could also be caused by a bad crankshaft position sensor (CPS).

    Part #: M05235377
     

    Road Race Build 4K  10  25

    1998 Mitsubishi Eclipse N/T
    fwd · manual · 2G DSM

    79  5

    1998 Ford Mustang GT
    rwd · manual · Misc Vehicles
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  7. Slow_Rs

    Slow_Rs Probationary Member

    10
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    Joined Oct 23, 2020
    glasgow, Kentucky
    what’s the best way to test it?
     
  8. BLACK'98DSM

    BLACK'98DSM Proven Member

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    Hoover, Alabama
    Not sure, but it's only a $20 part and it would only help, if anything, to replace it. Best way to tell the age is to see if the tip is worn down or if the o-ring is still in one piece. If it's never been replaced then I would go ahead and replace it regardless of how it looks.

    A few months back I spent a few hundred dollars on all new engine sensors just to be sure the engine was healthy.
     

    Road Race Build 4K  10  25

    1998 Mitsubishi Eclipse N/T
    fwd · manual · 2G DSM

    79  5

    1998 Ford Mustang GT
    rwd · manual · Misc Vehicles
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  9. Slow_Rs

    Slow_Rs Probationary Member

    10
    1
    Joined Oct 23, 2020
    glasgow, Kentucky
    alright i’ll also look into that, i appreciate the help!
     
    BLACK'98DSM likes this.
  10. Slow_Rs

    Slow_Rs Probationary Member

    10
    1
    Joined Oct 23, 2020
    glasgow, Kentucky
    i replaced the CPS and the MAP and it’s still doing the same thing, i am lost.
     
  11. BLACK'98DSM

    BLACK'98DSM Proven Member

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    What modifications have you done to the car? Anything that effects air intake or fuel delivery? You could just have a bad air to fuel ratio.
     

    Road Race Build 4K  10  25

    1998 Mitsubishi Eclipse N/T
    fwd · manual · 2G DSM

    79  5

    1998 Ford Mustang GT
    rwd · manual · Misc Vehicles
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  12. Slow_Rs

    Slow_Rs Probationary Member

    10
    1
    Joined Oct 23, 2020
    glasgow, Kentucky
    have an aftermarket header and a cold air intake, could o2 bank one sensor one not being plugged up cause the issue?
     
  13. Slow_Rs

    Slow_Rs Probationary Member

    10
    1
    Joined Oct 23, 2020
    glasgow, Kentucky
    i’ve also noticed when the car starts to act up it’s sounds like it’s trying to suck in as much air as possible
     
  14. BLACK'98DSM

    BLACK'98DSM Proven Member

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    Hoover, Alabama
    You mean you don't have the first O2 sensor plugged in? Yes, this could absolutely be the issue.

    It is ok to leave the 2nd O2 sensor unplugged because that only tells the ecu if the catalytic convertor is functioning. But the first O2 sensor determines how lean or rich and the car is running and adds fuel or air accordingly. Like I said, it could be a bad air to fuel ratio.
     

    Road Race Build 4K  10  25

    1998 Mitsubishi Eclipse N/T
    fwd · manual · 2G DSM

    79  5

    1998 Ford Mustang GT
    rwd · manual · Misc Vehicles
    Loading...
  15. Slow_Rs

    Slow_Rs Probationary Member

    10
    1
    Joined Oct 23, 2020
    glasgow, Kentucky
    makes sense looked at it this morning and the car didn’t even have one LOL, after work i’ll get it all plugged in and everything and see if it solves it.
     

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