Troubleshooters please

Lincoln Mark VIII

  1. joeynat

    joeynat Active LVC Member

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    I searched and tried some things other members have done but it hasnt worked.
    I have 3 problems whether their related I dont know.

    1994 Mark VIII 102xxx miles

    1. Takes a long time to start whether cold or after driving. During cranking it sounds like shes starving for fuel or like the timings off and when it finally starts the rpms go from barely idling (bucking) to a normal idle.

    2. Under WOT (when cold) she bucks like crazy with the rpms jumping up and down in harmony with the bucking. Its much worse when cold but you can feel the lack of power and slight bucking after its warmed up on the highway at WOT. I should mention this only happens under load not while in park.

    3. When coasting down the road with no throttle the rpms fluctuate from 45 mph down to 25 mph. Hard enough to rock my head forward and back.

    What Ive done in the last year...

    New fuel pump and filter
    New crank position sensor with pigtail
    New camshaft position sensor with pigtail
    Pulled out BOC performance chip
    New plugs and wires
    2 new coil packs
    No vacuum leaks
    Pulled each wire off the packs when running and the motor sputtered for each one.
    There were 3 error codes..... 511 Read only memory (ROM) test failure - KOEO 214 Cylinder Identification circuit failure (in continuous memory) 116 Engine coolant temperature higher or lower than expected (KOER)
    These codes are no longer there, removed chip, new camshaft sensor.

    I just ordered motorcraft plugs and wires. Everything else i changed was motorcraft except for the pigtails, and current plugs and wires.

    Any theories please...
     
  2. DLF

    DLF Dedicated LVC Member

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    What makes you sure that you don't have any vacuum leaks? What about the IAC?
     
  3. Right on the Mark

    Right on the Mark Dedicated LVC Member

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    What about your MAF?
     
  4. DLF

    DLF Dedicated LVC Member

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    +1 A likely suspect.
     
  5. joeynat

    joeynat Active LVC Member

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    Gave the MAF a shot last month, I sprayed the motor with carb and choke cleaner like madman.
     
  6. Sapperfire

    Sapperfire Dedicated LVC Member

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    What's "gave the MAF a shot" mean?... a year ago? Is that the last time you changed the air filter?

    Does the idle bounce when sitting still?
     
  7. warrioralumni08

    warrioralumni08 Dedicated LVC Member

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    I would also vote MAF or IAC. Usually, mine used to start up horribly, choke, bog down, and just have a rough idle. That problem went away, but these days if you don't let the car warm up, and try to take off right away, it will hesitate, bog down and not want to go, then all of sudden it just jump in rpms, and gets going. Also maybe a bad IAT sensor?
     
  8. chris2523

    chris2523 93 Mark VIII

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    mine did that. wouldn't rev. then after warming up for a while, ran great.
    it was the O2 sensors.
     
  9. joeynat

    joeynat Active LVC Member

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    "cleaned" maf last month k&n airfilter cleaned at same time.
    Can it be anything else besides the IAC. Is it possible the MAF itself went bad ? Wouldn't the MAF and o2 sensors throw a code ?
     
  10. 87TTOPGT420

    87TTOPGT420 Dedicated LVC Member

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    unplug maf and road test
     
  11. chris2523

    chris2523 93 Mark VIII

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    only if they are dead or WAY out of whack.
    if they just suck, no, you probably won't get a code.
     
  12. joeynat

    joeynat Active LVC Member

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    Where is the IAT sensor ? Ill unplug it tomorrow I didnt think the maf can cause havoc like that. Thanks everyone.
     
  13. warrioralumni08

    warrioralumni08 Dedicated LVC Member

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    Thanks! I will try that, it's no big deal, just annoying lol.

    Sounds like, you are trying to get away from tackling the IAC and are terrified of it? Also, as stated above unplug it, and see if the problem still persists.
     
  14. warrioralumni08

    warrioralumni08 Dedicated LVC Member

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    Intake tube, towards the throttle body.
     
  15. Sapperfire

    Sapperfire Dedicated LVC Member

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    Unplug the MAF and it'll barely run, yeah its kinda sensitive to it. What did you "clean" the MAF with?

    Does the idle "bounce" when the car is parked and idling?
     
  16. chris2523

    chris2523 93 Mark VIII

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    MAF is probably the main input for the EEC. TPS is huge too.
     
  17. joeynat

    joeynat Active LVC Member

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    I used maf cleaner. IAC and TPS I would like to avoid just by reading past threads especially on a gen 1. Im going to have to face them sooner or later it seems. Im thinking there out of my mechanical range.
     
  18. Sapperfire

    Sapperfire Dedicated LVC Member

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    Will you answer my question?--- that I've asked you twice
     
  19. 87TTOPGT420

    87TTOPGT420 Dedicated LVC Member

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    no it will run in limp mode...but it will start..idle just fine and even have most of its power and quickest way to rule out a faulty maf
     
  20. joeynat

    joeynat Active LVC Member

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    Very sorry Sapper, I would have to say yes but not all the time. Waiting at a red light after a 45 min drive last week the tach needle would fluctuate a bit with a rough idle but next day it was fine. What are you thinking ?
     
  21. NetKeym

    NetKeym Dedicated LVC Member

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    If you unplug the MAF on an engine that runs correctly, the car should still run fine, maybe slightly worse. That is an easy test that every one should know.

    If your engine runs much better with the MAF unplugged, then you found a problem - clean or replace the MAF.

    Believe it or not, when I first got my LSC on the road, I ran around for 3 months WITH THE TPS UNPLUGGED (I had no idea and just happened to see it one day while looking for vacuum leaks)! They work together, so your engine should run with just the MAF unplugged (by running off the TPS) or just the TPS unplugged (by running off the MAF), but will not run with them both unplugged.
     
  22. joeynat

    joeynat Active LVC Member

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    Just unplugged the maf and started the car. Instant CEL and it ran like crap !
     
  23. Sapperfire

    Sapperfire Dedicated LVC Member

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    I'm thinking TPS now that youve eliminated the MAF. Possibly a failing IAC as well, your wiper cowl needs to come off for either

    I suggest that neither be replaced with used ones
     
  24. NoLimit95

    NoLimit95 Dedicated LVC Member

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    I'm with the TPS too. It can make a Mark do crazy things when bad. IAC should be changed while you're back there and cleaning the throttle body isn't really a good thing.
     
  25. NetKeym

    NetKeym Dedicated LVC Member

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    I'm gonna third the TPS problem.

    Try unplugging the TPS (with the MAF plugged in of course) and driving it around - see if it runs better.

    Oh, BTW, I've changed the IAC valve on my Mark and plugged and un-plugged the TPS - it IS a total PITA because there is VERY limited space back there. I didn't remove the wiper cowl, but I will if I have to do anything back there again! lol
     

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