Burnt valves, weak coil, exorcism. (AGAIN-plz read)

[hombre@elp.rr.com (John Erickson)]

Well, it might be the coil, but they tend to be heat sensitive as they=20
fail.  They tend to be OK when cold, but get progressively worse as they=20
warm up.  The Bentley test would not detect this, of course.  When my coil=
=20
failed, the car would always idle fine, but the car would start to miss at=
=20
high RPM.  The worse the coil got, the lower the RPM where it would start=20
to miss.

If you had a burnt valve, the failure would be consistent (all the time at=
=20
all RPMs).

Can you get your hands on another distributor to see if it makes a=20
difference?  It might be the Hall sensor.

HTH

John


At 11:13 AM 3/21/2002 +0800, Dan Miller wrote:
>I have a 1988 16v rocco with 116 grand on 'er.
>The car starts DECENT but
>not right up.  The idle is finicky-the tach seems to
>be having a siezure
>at idle, moving up and down about 1/16th of an
>inch about 5-8 times a second-and
>sometimes the engine cannot find idle.  300
>rpm-1200-300-1200 etc.  The
>engine also misses-almost seems like 1 of the 4
>cylinders isnt firing regularly.
>but this is not a constant problem.  it is
>intermittent.  sometimes the
>engine runs fine-below 4 grand- and sometimes
>it runs, well, worse than
>a 3 legg=E9d dog.  The engine almost always just
>sputters above 4 grand, but
>sometimes pushes through it and revs all the way
>to the orange.  here is
>a complete list of the parts i have replaced and
>the tests i have done:
>
>REPLACED: fuel filter, coolant temperature
>sensor, thermotime switch, ignition
>control module, lambda sensor (OXS)  and
>control unit, BOTH fuel pumps,
>plugs (many times- the car loved to load em up b4
>i replaced the o2 sensor),
>wires, cap, rotor.
>
>TESTED:  differential pressure regulator, hall
>effect sender, idle air regulator,
>idle and full throttle switch, compression, timing,
>timing advance
>
>there are no vacuum leaks and no bad grounds.
>
>I have done a resistance test on teh coil as per
>bentley and the numbers
>were dead center.  Does this mean the coil is
>DEFINATELY good?  or can a
>coil start to fail at high RPM's or be weak? Also, i
>have a friend who had
>similair problems on his car(1974 superbeetle),
>and found it was a single
>burnt valve.  Has anyone had any experience with
>a burnt valve in a 16v
>rocco?  i am running out of parts to replace that
>could fix the problem,
>and running out of parts to replace, period.  Not to
>mention my left asscheek
>is starting to hurt because the padding in my
>wallet is getting thin.  If
>anyone out there can contribute a helpful word,
>HELP ME PLEASE!
>
>thinknig of giving up and selling car to junkyard,
>Dan Miller
>
>if i shoot my roocco between the headlights, will it
>roll over an dlook
>like this?
>
>[ X ][ X ]=3D=3D(/V\)=3D=3D[ X ][ X ]
>--
>
>......................
>
>
>
>
>
>
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