[xj] Re: Lumpy idle is good

John wrote:

Today my lumpy idles saved my car. I was going to take my six
year old to
grandma’s house, so at 8:35am I started my car to let it warm up.
Back in
the house I got busy on the phone, paperwork etc. At 10:15am I
told my son,
let’s get going but I could not find my keys. They were in my car
which had
been idling for almost two hours. I ran out but the car had
stopped. I
heard a ticking sound, tried to start her but the battery was
dead. A
battery charge started her right up. I can only assume that
because of a
lumpy idle, at some point, the car stalled. I don’t know how
long she ran,
if she overheated, etc. but all seems OK. I guess today 'm glad
for a lumpy

This episode puzzles me quite a bit. Why did the engine’s failure
to idle reliably “save” the car? From what peril was it saved?

Why shouldn’t a Jag be able to sit and idle quietly for an hour or
two? Recently, I was caught in a vast traffic jam that resulted
from an accident on a major highway. We stood still for about two
hours, during which time my XJ6 purred contentedly, tranny in
neutral, parking brake set, with radio playing and heater running
(very cold day). There was no overheating, silky-smooth idle with
no roughness of any kind, and plenty of oil pressure… exactly
what one would expect of a Jag, and as comfortable as sitting in my
own living room.

– Carl Ratner
'86 XJ6
'79 XJ12L