Hi there.

I know I don't post about the XK8 too much,
but it's an '03 with 74k miles on the clock.
N/A 4.2.

The car idles at about 600 rpm when warm.
It has a fairly nervous-feeling, rough idle.
And it isn't bad fuel, It has had BP 93 octane
in it for some tanks now.

Along with this rough, shaky, nervous idle,
when you give it 1% throttle, for example,
it drops in revs to near-stall. Every time you
rev it, when it isn't in gear, it plummets in
RPMs to near stalling. Under a gearbox load,
shakiness increases, but no stall propensity.

The throttle tip-in is also very sharp (which
leads to a bit of hesitance in the travel
just beyond tip-in) , but
I don't know if it has to do with the rough idle.

On to the noise: At idle, it is nearly silent,
but at anything over 600 rpms there is a clattering,
almost purring sound from the engine bay.
It is only easy to hear, when, say, parking,
when you are under 1000rpms, but not
at idle. It sounds to be coming from a plastic
fan, hitting the shroud or something.

Ian

 

HI,
im the wrong person to responding to your thread, but it just scared me you might have a timming problem, perhaps created by tensioners failing. I may be completly off track, but the continual rattle at tickover and missfire could be symptoms of the above.

id stop running the engine until someone else can give you a better idear on the forum. but if the issue is tensioners and timming then it is most important to investigate this NOW.

Hope im completly wrong, I just read your post and it makes sence to me.

best wishes

steven

 

As regards the idle and throttle issue, when was the last time you changed the fuel filter?