My Sixty Special is explosive
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Cadillac DeVille 1985 to 2005 including:
1985-1992 Fleetwood, 1993 Sixty Special, All FWD Forum Discussion, My Sixty Special is explosive in Past Cadillac Vehicle Discussion; So i was drivin down the highway when all of a sudden.......
  1. #1
    DReffects's Avatar
    DReffects is offline Cadillac Owners Fanatic
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    My Sixty Special is explosive

    So i was drivin down the highway when all of a sudden....














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    MoistCabbage's Avatar
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    A "muffler report".

    It's running rich, and the fumes in the muffler ignited.

  4. #3
    DReffects's Avatar
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    Re: My Sixty Special is explosive

    Quote Originally Posted by MoistCabbage View Post
    A "muffler report".
    Is this a common thing then?

    It's running rich, and the fumes in the muffler ignited.
    Hmm i had a defective catalytic converter. The inside of the converter was totally broken down. We cut out the converter and replaced it with a pipe. (for the time begin) The Garage suggested (at that point) that it might be possible that a piece of the converter went all the way back to the muffler. I then drove around für ~500 miles until the muffler exploded. The car was veeeerrry unsteady at times, especially in idle and when sloooowly accellerating. Right before the big bag the engine startet stuttering (i was going around 70MHP). In the past a firm press in the pedal resultet in restoring a normal behaviour. So that's what i did: i shifted down to 3rd gear and put the pedal to the metal. BANG!

    Could this still be fumes in the muffler or was it just stuck from some piece of the converter? Since my muffler is blown I haven't that that stuttering in idle

    How would I diagnose an engine (4.9 V8 FWD) running rich? The spark lines have been replaced and ingition timing was set by a garage before i got the car. I've ordered a new catalytic converter and a fancy quiet-sound Walker Muffler plus Spark Plugs.

    Thanks

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    MoistCabbage's Avatar
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    Common? No


    Running rich is usually what melts the converter. It's not very likely that anything was stuck on the exhaust, and that wouldn't have caused the muffler to burst.

    Have you ever checked the FPR?

  6. #5
    c_d
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    Re: My Sixty Special is explosive

    Assuming hat your can cannot generate long/short term fuel trims then with a good multi-meter at the O2 sensors: just observe the O2 cycle (like a sine wave) and the upper/lower thresholds. The sensor itself logs between 0V and 1V. As a rule of thumb (hopefully for your specific model, too): with a cheap tool, a MEAN output voltage between 0 and 0.45V is considered lean, 0.55-1.0V means rich.

    With a graphing multi-meter you'll see something more or less closely resembling a sine wave and you can read lean/rich conditions right away. More expensive meters with higher resolutions are fast enough to show you the cycling (going from +/- from a median of 0.5V). Remember to measure at an upstream sensor. Viel Glück.

    How did yuo make it through the ASU with just a pipe instead of the catalytic converter?

  7. #6
    DReffects's Avatar
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    Re: My Sixty Special is explosive



    FPR=Fuel Pressure Regulator? If so: no So the fuel pressure could be too high?

    ----------

    Quote Originally Posted by c_d View Post
    Assuming hat your can cannot generate long/short term fuel trims then with a good multi-meter at the O2 sensors: just observe the O2 cycle (like a sine wave) and the upper/lower thresholds. The sensor itself logs between 0V and 1V. As a rule of thumb (hopefully for your specific model, too): with a cheap tool, a MEAN output voltage between 0 and 0.45V is considered lean, 0.55-1.0V means rich.

    With a graphing multi-meter you'll see something more or less closely resembling a sine wave and you can read lean/rich conditions right away. More expensive meters with higher resolutions are fast enough to show you the cycling (going from +/- from a median of 0.5V). Remember to measure at an upstream sensor. Viel Glück.

    How did yuo make it through the ASU with just a pipe instead of the catalytic converter?
    Gonna try that! Car's at the garage atm, have no access to it. ASU? My next check in October 2014 - that was only meant to be a temporary fix until i get a bunch of spare parts.

    So what you guys are saying: i HAVE TO find the underlying issue (and the converter ISN'T the issue) in order to have my new muffler not to blow again? ^^

    How can I check if a oxygen sensor is good or bad?

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    Submariner409's Avatar
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    Re: My Sixty Special is explosive

    The engine is running an overly rich fuel mixture for some reason - that destroyed the cat and that blew the muffler. It may not be O2 sensor(s). I would look at fuel injectors and the fuel pressure regulator first, then go for a serious ignition miss in one or more cylinders - all of which would dump raw or partially unburned gasoline into the exhaust system.

  9. #8
    DReffects's Avatar
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    Re: My Sixty Special is explosive

    thanks for the info. how would you guys test the injectors?

    My take on it would be: remove the injector, put 12volts to them while pumping cleaning agent into it.

    i have no idea how to test the fuel pressure regulator

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    Re: My Sixty Special is explosive

    Fuel injector coil winding wire is finer than human hair. Be VERY careful when simply putting "12 volts across it" - easy to burn out the coil. You should really use a service manual from GM as your guide for proper voltage/testing - or ask a Mercedes shop how they test their injectors - my guess is that your Cadillac injectors are made by Robert Bosch anyway.

  11. #10
    DReffects's Avatar
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    Re: My Sixty Special is explosive

    My Cadillac Service Manual states that it is possible to test the injectors with the AC Controls:

    E.5.4. - While in this mode, each of the eight fuel injectors can be individually selected and turned "OFF" using the ECC "Warmer" and Cooler" buttons.

    Unfortunately i don't get the point of doing this

    From another forum: "A common problem with these 4.9L V8 is that the fuel injectors are notorious dogs, and the original designs were problematic. The resistance ranged from 1.7 ohms on #6 injector to a normal range of 15.8 on others. The problem was only two injectors were normal or working!! Others were in a range of 7 to 11 ohms."

    I'll talk to my mechanic tonight

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    Ranger's Avatar
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    Re: My Sixty Special is explosive

    Quote Originally Posted by DReffects View Post
    i have no idea how to test the fuel pressure regulator
    Locate the FPR (A). It's the small canister on the fuel rail near the TB. With the engine at idle, pull the vacuum line (B) and look for any signs of raw fuel. There should be none.


  13. #12
    DReffects's Avatar
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    Re: My Sixty Special is explosive

    SUPERB! Thanks!

  14. #13
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    Re: My Sixty Special is explosive

    Quote Originally Posted by DReffects View Post
    SUPERB! Thanks!
    -------------------------
    measure the resistance of the injectors -
    if they are not in "speck" replace them -

    the "defective" ones could be dumping more fuel than they are supposed to -
    over time - that could be what destroyed the cat -
    and when the cat stopped working - raw fuel built up in the muffler - and went BOOM! -

    I bet it "woke you up" when it popped! -

    ----------------

    here is a little tip on fuel injectors for the Cadillac 4.9 motor -

    19# injectors for a Ford 4.6 work better - and might be cheaper -

    the stock injectors are a two-pattern spray -
    with only 2 little holes that shoot fuel -

    the 19# Ford 4.6L injectors are a four-pattern spray -
    and are more efficient at dispersing fuel with air.

    they are direct replacement -
    HOWEVER the upper "O" rings were switched from the old injectors -
    for a slightly better seal -

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    Re: My Sixty Special is explosive

    Thank God you didn't blow up the red Porsche in the background!

  16. #15
    MoistCabbage's Avatar
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    What red Porsche?

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