[xj-s] V12 Rough Idle Cured

I have just run around the garden punching the air shouting yes ,yes. Why,
because after 2 years of suffering an incredibly annoying idling fault in
which the car refused to idle cold above 400 rpm I have now finally cured

When I posted the problem on the list over 12 months ago it was suggested to
me that it could be the crank pulley key was worn giving me a false ignition
advance reading. I checked the pulley by slackening of all the belts and
rotating the engine to TDC. This I determined by making up a probe which
screwed into the sparkplug hole and enabled me to make minute adjustment to
determine absolute TDC. I then checked the crank pulley to check it was
reading 0 degrees. As it was spot on, I put everything back and continued to
check/replace anything I could think of which could cause it. To no avail
nothing I replaced rebuilt checked made a damn bit of difference.

When my timing chain adjuster failed just before Christmas I decide to spend
the winter months rebuilding the front end, after removing all the ancillary
stuff off the front and pulling the radiator I was left with the crank
pulley. When I went to undo the nut I found that the pulley could be
rotated 20 degrees or so and after removing the bolt found the woodruff gear
half worn through and the keyway in the damper cone and the crank twice
their original size.

I have now replaced the damper cone JB welded a new crank key in place
torqued the crankbolt to 150 lb/ft and included a dab of Loctite in
strategic places. The car started fine but again idled at 400-500 Rpm,
however after checking the timing I found it had totally shifted position
now showing 0 degrees instead of the 18 degrees I was seeing before.

Reset the timing and she now runs like a dream, Can’t believe it. Any of you
guys will know how satisfying it is when you finally fixed some irritating
fault and have the old girl running sweet again. Much better than handing
over a cheque to someone else!

Moral: when you think you’ve checked your crank pulley check again.

Now to explain to the wife what i was doing in the garden…

1982 XJ-S HE

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