XJ6 Rough idle

[Mike Meadows <74127.1022@CompuServe.COM>]

I'm almost out of ideas and hope that someone can help.  I have just joined this
mailing list and hope that a similar question has not been posted recently.  My
1986 XJ6 4.2 runs rough - not a steady rpm at idle, and has lost a some power
when accelerating.

Symptoms:
The idle rpm when in park is between 800 and 900 rpm.  The effect is worse when
shifting to drive where the rpm is between 500 and 600.  Every few seconds there
is a sudden drop in rpm of about 100.  There is no pattern i.e. it does not
happen at a reagular 'beat'.

When the engine is cold (left off for many hours), the problem is not apparent.
It is only once the engine has warmed up does the problem really show up.

When accelerating, there is a pinking/knocking sound from the engine.

May be unrelated, but there are drips of water coming out of the exhaust system
along with a little white smoke.

Things Checked:
Spark plugs are new and set correctly to 0.035ins.  A little soot on bodies,
grey on the electrodes.
Oxygen sensor recently replaced in order to pass new Texas emissions test.
Timing is fine - 18 BTDC
Vacuum readings are 19.5 plus or minus 0.4 mmHg at idle.  On full open reads
somewhere between 0 and 4 mmHg.  On release of throttle, goes to 26 then slowly
back to 19.5.
Air temp sensor in Flow meter is working and within calibration, same with the
coolant temperature sensor.
I disconnected the electrical connector to the cold start injector but saw no
change with the engine warm.  I was hoping the Thermotime switch or the relay
was staying on after the engine had warmed up.

I'd appreciate any ideas,
Mike Meadows

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