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1995 355 misfiring

Discussion in 'Technical Q&A' started by billy89tr, May 30, 2004.

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  1. billy89tr

    billy89tr Rookie

    Oct 31, 2003
    20
    #1 billy89tr, May 30, 2004
    After letting the car sit for a couple of months. I took it out for a ride--everything was going great. I fill up the car with 93 octane shell gasoline and 10 minutes later the car backfired while shifting from 1st to 2nd. Now the car idles runs and misses. No check engine light or anything. Could it be bad gas? I have put all sorts of additives but nothing helped. I took out the plugs and it seems one of the plug wires is rusted as if water seeped through. Anyway plugs didn't look too bad but probably were the originals almost 10 years old now. I ordered iridium plugs and am waiting to receive them to put them back in and check. Other than that has anyone ever had a problem like this? What else could it be or is it bad gas? THanks for any help.
     
  2. richard_wallace

    richard_wallace Formula 3

    Feb 6, 2004
    1,957
    Cincinnati, Ohio
    Full Name:
    Richard Wallace
    #2 richard_wallace, May 30, 2004
    I would have guessed gas first, plugs second. Which you are already on...

    It probably wouln't be a bad idea to drain the tank and make sure you have no goop in the tank... if you are getting strong gas smells - could be bad gas, fuel filter/pump, etc.

    The other thing you might try - is to cut power to all the ECUs (green cut-of knob in the front luggage area.) Turn this off for a few minutes. Turn it on, with all things turned off in your car (AC, Radio, Radar, etc.) Let it idle for 10 minutes without touching the gas... Let the ECU relearn and see how she goes...

    Rich
     
  3. rexrcr

    rexrcr Formula 3
    Rossa Subscribed

    Nov 27, 2002
    1,578
    Kalamazoo, MI
    Full Name:
    Rob Schermerhorn
    #3 rexrcr, May 31, 2004
    You're on the right track. A misfire without any MIL is a strong indication of ignition system issues. The coils are being told to fire the plugs, but something is going wrong from there. Spark plug firing is not monitored in Motronic 2.7.

    Check grounds too. Any corrosion may also cause an issue.

    Erasing the ECU's memory won't hurt anything as you don't have any errors stored. BTW, only takes a couple of seconds to reset the ECU with battery disconnect, and yes, about 10 minutes or so of idling without touching the throttle to re-initialize.

    And like Rich stated, fuel is suspect.

    Best regards,

    Rob Schermerhorn
     
  4. chaa

    chaa F1 Veteran

    Mar 21, 2003
    5,058
    #4 chaa, May 31, 2004
    When i know i am going to leave my cars or bikes stood for long periods i always use fuel Stablizer, it stops the fuel from going of. It is added in small amounts to a full tank of gas.
     
  5. Dr_ferrari

    Dr_ferrari Formula 3
    Consultant Professional Ferrari Technician

    Nov 2, 2003
    1,071
    Pocono Sportscar
    Full Name:
    Jim McGee
    #5 Dr_ferrari, May 31, 2004
    Remove the plugs and inspect. you will most probably find them fouled. Also check the ignition wires under the covers for water/corrosion. a lot of times you will get water under the covers that when the engine warms up causes all sorts of ignition misfire problems.

    A good place to start...

    best regards, Jim
     

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