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Weird Misfire 1996 Mark

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  • Weird Misfire 1996 Mark

    1st gen with only 75K miles started to misfire at low rpm (1200-1400) under load. No code, no engine light. Only happens when car is warm so smooth as silk for 1st 5 miles or so. Tried to simulate condition in driveway by putting in reverse applying brake and running the revs up. Car said "Nope, not gonna misfire cause ya want me to." So knowing it never had a tune up this is what I have done:

    Replaced plugs and wires (Motorcraft)- No Change
    Replaced Coils (MSD)- No Change
    Replaced fuel filter (Motorcraft)- No Change
    Replaced Fuel pump (Walbro)- No Change... well she does start quicker
    Cleaned MAF sensor- No Change
    Replaced air filter (Motorcraft)- No Change
    Poured a butt load of Sea Foam in tank- No Change... bet my engine is super clean now.
    Only use premium gas

    If ya punch it she runs like a raped ape, highway speed is smooth and steady, this car only hacks up fur balls when you drive slow ~30-45 mph. I'm at my wits end, hopefully someone has a magic fairy wand and can wave it over my car. Suggestions would be marvelous, solution would be awesome! Thanks in advance for any help.

    Bear

  • #2
    Could be a vacuum line. Gen 1 has a line that sits on the intake manifold about 1/2 way back. Check under dash. A line could have a slow leak, and when you rev it up, it gets enough vacuum.
    94 MK VIII
    95 MK VIII
    98 MK VIII CE # 87
    04 Chevy PU 3500 4X4

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    • #3
      I don't see a Throttle Position Sensor on your list of replaced parts. It's cheap, and easy to replace. (on the 2nd gen, anyway.) It could be a factor here.

      The part is basically a variable resistor - think the volume knob from that old stereo that "crackles" when you turn it within the area you want to set it at, but works fine at high volume where you don't use it as much.
      Mike Martin

      1997 Mark VIII LSC 5.0
      2001 Dodge Dakota

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      • #4
        Thanks OnlyTony, will search anything vacuum related.

        - - - Updated - - -

        Thanks Tixer, will purchase TPS after vacuum line check.

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        • #5
          UPDATE: Still having the problem. Looked at the vacuum more closely and still don't see anything out of the norm. Buying a TPS tomorrow and hope to install it this weekend barring family interference. I will update as I move through the issue.

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          • #6
            so are we sure its not converter shudder?
            1996 Lincoln Mark VIII LSC Opal Opalescent on grey, 276/287
            1995 Lincoln Mark VIII LSC Indigo Lights on black
            2002 Ford Focus SVT Sonic Blue on black

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            • #7
              Sound like front 02 sensors..my 98 did the same exact thing . No cel . But it did come on once for a day ..changed front 02 sensors with 10$ no name eBay ones and it's ran great ever since..lol I too did coils,plugs,mafs ect...
              98 lsc..trac loc,cobra cams,90mm mafs,exhaust,tune,accel coils,DS rotors and ceramic pads,rims and sounds too.

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              • #8
                Originally posted by chris2523 View Post
                so are we sure its not converter shudder?
                When I first got my 95 (18 years ago), I had the same problem when at low speed shifting into od, it would shutter. Trans filter, and Mercon 5 fixed it. Chances are you have Mercon 3 in it. Good call Chris.
                Try it with the OD off.
                94 MK VIII
                95 MK VIII
                98 MK VIII CE # 87
                04 Chevy PU 3500 4X4

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                • #9
                  UPDATE: After going through all the obvious, I bit the bullet and torn into the fuel injectors- not a fun job. They were really bad which in turn caused the drivers side converter to overheat and basically have a melt down. So two problems found and fixed... sort of. I replaced the fuel injectors and there was definite improvement but car still would hiccup, that's when the converter was noticed to be crazy hot. (thermal scan). If you don't know, that sumbeatch is the exhaust manifold/converter all rolled into one part- BAD FORD/LINCOLN. To add insult to injury the steering shaft is another bonus item to work around. The EGR tubes on mine would not separate from the manifold. Guess what- can't buy them from anyone but salvage- if you can find it. Soooo long update longer, I punched a hole in the converter to let her breath again and am currently looking for headers that fit the Lincoln and will eliminate ALL converters and resonator. I am also going with a cobra intake to eliminate the butterfly valves in the marks intake. I have an extra ECU I will send out for reprogramming. So car fixed, sort of. Thanks to EVERYONE for your help, it is much appreciated. I hope that this trip down misfire lane helps other Mark Viii lovers out there.

                  Bear

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                  • #10
                    kooks makes "bolt in" headers.
                    i am pretty sure there is a magnaflow replacement cat out there for the one piece side.
                    cobra intake does not delete the IMRCs.
                    deleting the IMRCs does not require a cobra intake.
                    1996 Lincoln Mark VIII LSC Opal Opalescent on grey, 276/287
                    1995 Lincoln Mark VIII LSC Indigo Lights on black
                    2002 Ford Focus SVT Sonic Blue on black

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                    • #11
                      Use Cobra exhaust manifolds and have your exhaust guy mate up the exhaust with a set of downpipes.

                      JP

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