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runs rough when cold

My 1998 Jeep wrangler runs rough until it gets warm. It sputters and backfires until it clears and then it runs fine. There is a slight smell of fuel when it is sputtering but goes away once it clears. I have replaced plugs cap wires and rotor but it didn't help.
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Comments

  • edited July 2010
    Any check engine light on? Sounds like it's not getting the correct amount of fuel.

    Could be something like a temp sensor.

  • edited July 2010
    So this is only from a cold start? As Goldwing said, and given the smell of fuel it sounds like you're running rich. It should run a little rich when it is cold - that's why the temp sensor might play in since the computer uses its info for fuel metering.

    I'd be tempted to pull and clean the idle air control (IAC) valve. The smell of fuel says that you don't have a fuel shortage - but you might have an air shortage.
  • edited July 2010
    It might even be an injector leaking fuel after shut down. The sputtering could be from excess fuel causing a too rich condition before the excess fuel burns off. Just a thought.
  • edited July 2010
    It idles fine. This problem happens when I accelerate or load it and will go back to idle okay if I back off. If I stomp on it it will take off like a bat out of hell and then will clear and be fine. It's only giving me a problem when cold and I am accelerating normally. It sputters, backfires, a slight smell of gas and will clear up in about a half a mile to a mile. It will then run fine as long as I wish to run it.
  • edited July 2010
    Any Check Engine light on????
  • edited July 2010
    No engine lights are on and there are not any engine fault codes reading either.
  • edited July 2010
    Is it harder to start?
  • edited July 2010
    Nope. It starts fine and seems to run fine once it's warm. When I replaced the plugs, cap and rotor there were no indications on the plugs of it running rich. In fact they looked to be in pretty good shape color wise considering 75,000 miles
  • edited July 2010
    Clean the throttle body and mass airflow sensor (MAF).
  • edited July 2010
    I just went out and unplugged the ox sensor on the manifold and drove it around the block. It didn't buck or sputter but I could feel a slight miss and it smelled like it was running a little rich. It's the best it's ran from a cold start yet. I just don't know how it should run with the ox sensor unplugged. Any thoughts?
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