355/series of mini, muffled backfires, gargling. | FerrariChat

355/series of mini, muffled backfires, gargling.

Discussion in 'Technical Q&A' started by beezerhound69, Jun 29, 2004.

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  1. beezerhound69

    beezerhound69 Karting

    Feb 3, 2004
    136
    Suwanee
    Full Name:
    Tom
    #1 beezerhound69, Jun 29, 2004
    Hello all,

    A little history on the car. I've got a '97 355 with 2800 miles on it. I've owned for 5 months and have put 1400 of those miles on it myself. I bought it with the 30k service already done to it. Things have been great until a few weeks ago.

    Can anyone identify this problem? I fire up the engine and let it sit 5 or 10 minutes to get up to temperature. Here and there I'll hear one , two, or maybe every now and then a small series of backfires for lack of a better word, without the backfire noise. It's muffled , almost like the engine is skipping a beat or something. When I get going and lay hard into it , things are good, then the skipping/muffled noise can really pick up a bit at traffic lights after the car has been running a while. From there, when I take the clutch off and go into 1st gear, often times it's almost like it's gargling, lacking power, and then all of the sudden it's gone and the engine comes roaring back.

    Thoughts?
    For the life of me, I can't figure it out.
     
  2. tbakowsky

    tbakowsky F1 World Champ
    Consultant Professional Ferrari Technician

    Sep 18, 2002
    19,378
    The Cold North
    Full Name:
    Tom
    #2 tbakowsky, Jun 29, 2004
    Sounds like a miss on one or more of the cylinders to me.

    Have you recently washed down the engine..or have you in the past? Somtimes water can get under the plugwire cover plate and cause all kinds of funny things to happen.

    You could also check the condition of the ignition wires by checking the resistance with an ohm meter. Also have a look at the extention for burn through. Rare to have burn through but I have seen it before.

    Also check the plug condition. A nice sandy color to the plug is normal. If you find some plugs to be black in color that may well be your miss fireing cylinder. Also look for oil diposits on the plugs electrode. If you find a hard and crusty build up on it..it may be an indicator of a valve guide issue.

    Check all tha basics aswell like compression and a leak down with engine cold and then warm and compare readings. The more reliable reading will be the warm readings obviously.

    You could(if nothing found with other tests) check fuel pressure and fuel filter for clogging. I have seen a couple of 355's with coked up throttle plates. After cleaning the cars ran great. This can cause a difference in airflow to each cylinder causing a rough and stumbly idle. But these were higher mileage cars that were more or less city driven and saw lots of stop and go traffic...these guys used their cars as a daily driver and used thier boats on the weekends(must be nice!!)

    HTH

    Tom
     
  3. beezerhound69

    beezerhound69 Karting

    Feb 3, 2004
    136
    Suwanee
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    Tom
    #3 beezerhound69, Jun 29, 2004
    Assuming the 30k service was done, wouldn't plugs, valve guides, etc. have been looked at?

    Just curious, I am trying to learn this stuff, but still quite the amateur.
     
  4. tbakowsky

    tbakowsky F1 World Champ
    Consultant Professional Ferrari Technician

    Sep 18, 2002
    19,378
    The Cold North
    Full Name:
    Tom
    #4 tbakowsky, Jun 29, 2004
    That all depends on how closely they inspected the car. If they just did belts and couple of small other items then really that is not a full 30k service. Many times things like checking the basic are overlooked in the name of getting the car in and out as fast as possiable. Somtimes many things are not done becuase of shortage of time or the customer or dealer does not want to spend the time to look more closely if the car "seems to run o.k"
     
  5. Merdav

    Merdav Formula Junior

    Apr 11, 2004
    980
    #5 Merdav, Jun 30, 2004
    CATS could be clogging the exhaust, pretty common for a 355 and something the 30K wouldn't have noticed. Would also give a low RPM gargling sound, a little rattle a low RPM also?
     
  6. ze_shark

    ze_shark Formula 3

    Jul 13, 2003
    1,274
    Switzerland (NW)
    #6 ze_shark, Jun 30, 2004
    I'd also give a check to the headers/manifold, try to determine if you hear a pffft noise from either side of the car when it's cold. Leaking manifolds do have an effect similar to what you describe, a kind of greasy garbling sound so ...
     
  7. beezerhound69

    beezerhound69 Karting

    Feb 3, 2004
    136
    Suwanee
    Full Name:
    Tom
    #7 beezerhound69, Jun 30, 2004
    Another question, was the valve guide (if it turns out to be that) problem, acknowledged by Ferrari? ie. covered?
     

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