Misfire ?? Help Needed

Discussion in 'RT/10 and GTS Discussions' started by madbrian, Feb 20, 2010.

  1. madbrian

    madbrian Enthusiast

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    my 99 gts 12,000 miles has an intermittent misfire.
    runs great when on the gas, lots of bucking but not always when going slow.
    both throttle butterflies adjusted correctly.
    i have changed following and about to throw towel in

    plugs
    leads
    both coils
    cleaned all grounds
    both oxygen sensors
    air sensor
    fuel filter
    throttle body sensor
    map sensor
    cam sensor
    crank sensor
    pcm
    both cats ( 1 damaged through misfire )
    could it be an injector ? is there an easy way to check which one is at fault.
    cheers,
    Brian.
     
  2. Ratical2

    Ratical2 Viper Owner

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    If it is like my 96, you have 4 O2 sensors, not just 2. The other thing is battery condition. The car has a tendency to do weird things when the voltage is low.

    Looks like you have addressed all the other possibilities.

    Good Luck and post what you find that caused of the problem.
     
  3. plumcrazy

    plumcrazy Viper Owner

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    914-763-3136 ask for chuck.
     
  4. GTSnake

    GTSnake Viper Owner

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    How old are the spark plug wires?
     
  5. ViperJohn

    ViperJohn VCA Member - Northeast

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    Is the car throwing a misfire code? If it throwing a specific cylinder code then I would check that injector. You could also switch with another injector and clear codes and see if same code returns or if it has changed to the cylinder number that you moved suspected faulty injector to.

    I would also check the wires and one last thing I would check is to make sure your fuel pump is working properly. Best way to check is to buy a fuel pressure gauge and remove your cowl. Run gauge through opening and tape to windshield. It looks bad, but this will allow you to operate the car and check the fuel pressure through the entire vehicle operation cycle. If you notice fuel pressure drop during the bucking, chances are the fuel pump not supplying enough fuel is leading to a lean condition.

    I am also curious what type of damage the catalytic converter sustained.

    Another possibility is a bad PCM or bad ground to the PCM. I remember reading a few years ago there was a member struggling with bucking and once correcting a faulty ground, the bucking went away.

    Calling Chuck Tator is also really good advice.

    Good Luck.
     
  6. Viper Specialty

    Viper Specialty Viper Owner

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    You never said if the car was stock? Is it actually throwing a Misfire code, or just surging...?
     
  7. 99 R/T 10

    99 R/T 10 Enthusiast

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  8. madbrian

    madbrian Enthusiast

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    the only mods are headers, hi flow cats, 3 inch corsa cat back, k and n filter , smooth tubes.
    i have tried 2 sets of leads, now has new mopar gtsr leads.
    the damage to 1 cat consists of the exit side .if you look inside the cat the mesh is approx 3 inches further in than it should be and it looks distorted in shape not flat mesh like it should be.
    the pcm has been changed for a brand new 1998 one and the grounds have all been cleaned and extra grounds have been fitted.
    there are no misfire codes
    mainly the car just surges and often clunks from the drive train while this happens. it goes great when you step on it,
    the battery never fails to crank the car over so seems fine.
    any ideas??
    cheers
     
  9. plumcrazy

    plumcrazy Viper Owner

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    battery cranking and being fully charged is different. if you dont know the age of the battery or its 4-5 years old, replace it
     
  10. madbrian

    madbrian Enthusiast

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    the battery is over 5 years old , its very strong with no obvious signs of failure.
     
  11. white out

    white out Viper Owner

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    +1 for the injector.

    how old is the fuel in the car?
    have you checked the timing?
    any vacuum leaks?
    fpr or fuel filter could be causing an irregular flow.

    Nick
     
  12. Daddy Long Stroke

    Daddy Long Stroke Viper Owner

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    Did it ever throw a code that you cleared? Sometimes they don't seem to come back.

    Did you replace the 'front' two 02 sensors, or the 'rear' ones?
     
  13. 99 R/T 10

    99 R/T 10 Enthusiast

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    I would do 2 things right now. Get the injectors professionally cleaned by Tony Armour(1tony1) and change out the fuel filter. Both could cause issues if dirty.
     
    Last edited: Feb 21, 2010
  14. Jack B

    Jack B Enthusiast

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    Can you clarify whether the surge is low or high vacuum and at what rpm.
     
  15. madbrian

    madbrian Enthusiast

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    fuel is new in tank
    both o2 front sensors are new
    fuel filter is new
    checked fuel pump relay is in correct
    can't find vacuum leak
    the surge is at low revs below 2500 revs approx
    have not changed rear o2 sensors
    have not checked timing
    the car has not shown a code

    do you think it is possible there is crap or water in the gas tank?
     
  16. Jack B

    Jack B Enthusiast

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    Low or high vacuum - in other words, light pedal or way into the pedal? Is it a surge or is the car bucking.

    1. The rear O2'S won't affect it.

    2. Have you actually put a OBD reader on the car.

    3. You cannot mechanically change the timing.

    4. Are you sure the drivers side throttle opens slightly before the passenger side.
     
    Last edited: Feb 21, 2010
  17. Viper Specialty

    Viper Specialty Viper Owner

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    Without more detail, this is TOUGH.

    Personally, I would lean towards a leaky injector or a bad O2, which caused the cat to fail. I have also seen coils & PCM's that are intermittent, and you will go insane chasing them [usually gen-1's] The plugged cats make the surging worse. As we all know, most Vipers, especially 92-99, have a bit of low-speed buck.

    On that note, I have seen:

    1. Injectors/plugs/coils/O2's/etc causing cats to fail, misfires, surging.

    2. Cats fail for NO apparent reason, causing surging. Car was gone through top to bottom, NO other issues found, cat replaced, and did NOT ever reoccur. Still cant explain it, but I have seen it a couple times.
     
  18. madbrian

    madbrian Enthusiast

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    it happens at low vacuum and the drivers side butterfly slightly opens first.
    i checked it with a rowe obd reader, will this be good enough to display the fault?
    is there an easy way to locate which injector is at fault if any ?
    thanks!
     
  19. GTSnake

    GTSnake Viper Owner

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    If it has not thrown any codes I would lean more toward the fuel system. Sounds like an injector issue.
     
  20. Mike Adams

    Mike Adams Viper Owner

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    I would look at replacing the Throttle position sensor. Once a year have to do it on my dakota
     
  21. 99 R/T 10

    99 R/T 10 Enthusiast

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    Mike Adams, long time no see. Good to see you posting again.
     
  22. Joseph Dell

    Joseph Dell Enthusiast

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    And that 5 year old battery. I know you said it was cranking strong, but it is cheap insurance to replace it. If it isn't dead now, it will be soon.

    +1 on cleaning the injectors. Also, clean our your idle air control motor. That pesky thing sticking off the passenger side of the intake near the alternator. They often stick open or closed.

    Good luck!
     
  23. madbrian

    madbrian Enthusiast

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    the tps has been replaced, no difference
    i have cleaned the idle air control, no difference.
    i think it is time to buy a battery and clean the injectors.

    can the battery temp sensor cause this problem?
    perhaps something has been tipped in the gas tank before i purchased the car?

    i remember being in a gas station once and while a moped driver was paying for his fuel, 2 arseholes rammed gravy and chips into his tank.
     
  24. Jack B

    Jack B Enthusiast

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    If the issue is at low vacuum, that little devil (IAC) shouldn't be part of the problem.

    If you remove the injector connectors one at a time, you can hear/feel a slight roughness at idle each time you pull the connector. A totally dead injector won't change the current engine rhythm. That is a lot of trouble and the oem connectors are junk, you might end up worse for the ordeal. The rpm won't change much since the ECU will try and compensate for the lost injector.

    You could probably also watch IAC and if there is no change when you pull the bad injector you will not see a change in the IAC position. If it is a intermittent injector issue - good luck.
     
  25. Jack B

    Jack B Enthusiast

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    I just had Tony Armour balance my injectors - quick turn-around. If you do that, change the connectors to the MSD type, this way you will have ruled out an injector problem. It could still be a single coil-pack.
     
  26. madbrian

    madbrian Enthusiast

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    both coil packs are new and i fitted msd connectors ( the ones with a wire retaining clip that click when connected )
    i think it is time to remove the injectors and get them tested.
    do you think injectors can go bad at 12,000 miles?
    cheers!
     
  27. white out

    white out Viper Owner

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    Just pull the injectors from that bank (both for extra security) and take them to a local shop to have them bench flow tested and cleaned.
    If you don't have one local, Deatschwerks is a very reputable company and would do it for a reasonable price. But your car will be down for a few days.

    Nick
     
  28. madbrian

    madbrian Enthusiast

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    can any one tell me if all year viper gts injectors are the same ?
    i saw some on the net for sale and they listed different injectors for different year cars.
     
  29. 99 R/T 10

    99 R/T 10 Enthusiast

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    I believe they are all the same from 1996-2002, 29lbs injectors.
     
  30. Bobpantax

    Bobpantax Enthusiast

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    Have you tried a simple cure like disconnecting the battery for a period long enough to clear out all of the adaptives in the controller and then seeing if the problem is still there after you reconnect?
     

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