High RPM Bogging/Backfire Between Shifts

Discussion in '96-04 - 2V Specific' started by 98snakehorse, Jun 19, 2015.

  1. 98snakehorse

    98snakehorse Well-Known Member

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    My 98gt has been running great this season however recently I noticed some bogging and backfire issues which seem to be becoming progressively worse. I took the car out for a spin tonight and got on it down an off ramp and noticed everytime I went to shift in high rpm the car would backfire/studder and bog really bad into the next gear.

    Car has a complete PI engine brand new plugs/new fuel filter, red monster cop conversion (which has worked great), Brand new upstream O2 sensors. I suspected that the fuel pump may be going out as it had seemed a bit too noisy at times. I'm sure it's still the factory one 145ks on it.

    I've order a new fuel pump (walbro 255), We'll see if that clears it up; however this has me stumped as it has been running hard as hell for me tell now.
     
  2. Ferocious

    Ferocious Legend SN95 Supporter

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    Do you have a way to check the AF ratio? The backfire i'd assume is from running rich. If a new fuel pump does nothing, maybe check the injectors.
     
  3. lutter94

    lutter94 Well-Known Member

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    Doesn't hurt to seafoam it (fuel tank and vacuum), if you've never done it.
     
  4. 98snakehorse

    98snakehorse Well-Known Member

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    Injectors are sadly high mileage aswell. Its one of those things where I don't want to throw money at the wrong things so was hoping someone had similar issues as me. My guess is one of the injectors is failing, a coil pack could be going bad too. I suppose I can find another set of 19lb injectors cheap as I think that's what the orange ones are. I have some extra coil packs I can try swapping out. Ahhh I hate fighting these gremlins!!
     
  5. 96blak54

    96blak54 Legend

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    Unplug maf sensor and then go drive it hard. Report findings
     
  6. D3VST8R96GT

    D3VST8R96GT Well-Known Member

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    Spark plug gap?

    Sent from my SPH-L720 using Tapatalk
     
  7. 98snakehorse

    98snakehorse Well-Known Member

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    Spark plug gap is factory 0.052 which I double checked before I installed. I ended up disconnecting the negative terminal on the battery and resetting the ecu. Also swapped out a couple of coil packs and it seems to have cleared it right up. Pulls hard all the way up to redline.
     
  8. Musturd

    Musturd Legend

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    When my 96 did this it was because of a crack at the thermostat housing on the plastic intake and water was getting into the spark plug boot and causing a misfire it's just a thought pull ur spark plug wires out and check for moisture those plastic intakes are prone to cracking
     
  9. 98snakehorse

    98snakehorse Well-Known Member

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    My thermostat housing is the aluminum one and its doing good no leaks there. I also dont have spark plug wires as I'm COP. I'm thinking I got it fixed but just to be sure since my fuel tank is out right now because I'm putting a walbro 255 in. I'm going to delete the PPRV on the new pump which should resolve any other chances of high rpm fast shift bogs.