I am getting a very intermittent misfire at idle. By that I mean perhaps
2-3 times a month.
If the car is at idle you can hear and feel a very brief misfire…like one cylinder dropping out just for an instant…just a quick
“bump-bump” and its all over. That’s it… about as quick as you can blink
an eye. I reckon it may be happening while driving but I’ve never noticed
it.
I don’t hold much hope of tracking it down until the symptom becomes more
consistent but I thought I’d throw it out to the group anyhow
The car has 35K miles, 5K on new Champion plugs…can’t remember the number
offhand but they’re hotter range recommended by the group.
In reply to a message from Doug Dwyer sent Mon 26 Feb 2007:
Doug, maybe a coil pack going bad? Maybe even one of the
connectors to the coil pack getting a bit intermittent?–
The original message included these comments:
I am getting a very intermittent misfire at idle. By that I mean perhaps
2-3 times a month.
In reply to a message from Doug Dwyer sent Mon 26 Feb 2007:
Try reading the codes and see if something is there. Mine does this
now and then, has never developed into anything. If it gets worse,
maybe it can be isolated. If it has not set the MIL, it is probably
nothing to worry about.–
Brian Caro 96XJ6 4.0 63E-TypeS1FHC
Newport News, VA, United States
–Posted using Jag-lovers JagFORUM [forums.jag-lovers.org]–
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In reply to a message from Doug Dwyer sent Mon 26 Feb 2007:
I would disconnet/reconnect the coil leads. If you think about the
duty they pull in terms of cycles, and the fact they are pretty
light weight, it is quite possible a little contamination is
present. The plugs were changed recently, so maybe one of the
connectors is not all the way home. I find #6 , the odd ball, to
be the one that takes more push to get the connector on.–
The original message included these comments:
I am getting a very intermittent misfire at idle. By that I mean perhaps
2-3 times a month.
If the car is at idle you can hear and feel a very brief misfire…like one cylinder dropping out just for an instant…just a quick
‘‘bump-bump’’ and its all over. That’s it… about as quick as you can blink
an eye. I reckon it may be happening while driving but I’ve never noticed
it.
I don’t hold much hope of tracking it down until the symptom becomes more
consistent but I thought I’d throw it out to the group anyhow
The car has 35K miles, 5K on new Champion plugs…can’t remember the number
offhand but they’re hotter range recommended by the group.
No codes, no MIL. I’ll check the coil connectors as suggested and “wait for
further developments”.
Yeah, I agree it should be no cause for worry. Its just a little aggravating
when you know there’s a little glitch in there somewhere…
Cheers and thanks
Doug Dwyer
Longview Washington USA
1995 XJRFrom: “Brian Caro” bcaro@cmlarchs.com
Try reading the codes and see if something is there. Mine does this
now and then, has never developed into anything. If it gets worse,
maybe it can be isolated. If it has not set the MIL, it is probably
nothing to worry about.
In reply to a message from Doug Dwyer sent Thu 1 Mar 2007:
When it drops out, does the cyl completely misfire by the feel it
has through the drive train and steering wheel or is it more of a
rough ‘‘lope’’ while idling stationary after so many seconds and it
returns to normal idle for a stretch of 10-20 seconds and then lope
rough again?
I was never able to totally figure out what the cause of the rough
burp in idle was in my own car, but it went away almost completely
after a failed coil was replaced, and totally with new plugs, lots
of miles, and a steady supply of good octane.
Even with other things going wrong on the interior (or the exterior
when you’re attacked by angry mountainsides), the idle is still
good. Have you unplugged a coil to see if it’s the same feeling?
G/L to ya!
Sunny–
The original message included these comments:
One fellow replied to me off list saying that SKU Iridium plugs, BKR6EIX,
solved the problem on his XJR.
The one I’m referring to here is a sudden, quick misfire of (what feels
like) one cylinder, for one revolution---- one “bump-bump” and its all over
until the next time it happens. Say “bump bump” just as fast as you can and
that’s what it feels and sounds like. If a fellow could unplug a coil and
plug it back it within one second…and not an iota more… that’s probably
what this would feel like. Definitely feels like a secondary ignition type
of thing.
Since you mentioned it, I do also have come-n-go idle roughness, almost as
though a switch was being turned on-off. Not horribly rough by any
means…but a “little something”. I’ll observe more carefully to see if it
matches your description. I wasn’t gonna worry much about that until I
cleaned the t/body at least.
When it drops out, does the cyl completely misfire by the feel it
has through the drive train and steering wheel or is it more of a
rough ‘‘lope’’ while idling stationary after so many seconds and it
returns to normal idle for a stretch of 10-20 seconds and then lope
rough again?
I was never able to totally figure out what the cause of the rough
burp in idle was in my own car, but it went away almost completely
after a failed coil was replaced, and totally with new plugs, lots
of miles, and a steady supply of good octane.
Even with other things going wrong on the interior (or the exterior
when you’re attacked by angry mountainsides), the idle is still
good. Have you unplugged a coil to see if it’s the same feeling?
In reply to a message from Doug Dwyer sent Sat 3 Mar 2007:
The latter is the characteristic a large number of X300 owners have
come to accept though? Its not Lexus full glass on the hood with
no ripple commercialism smooth, but its torquey and won’t cause pre-
mature starter wear like the old V12’s can do!
That double bump is the exact same thing I could never figure out.
And its frustrating because its not persistant (every revolution).
I never felt it when it was cold and idling, only when the engine
and fluids were at operating temp.
If you can electronically control the idle to drop to say, 650,
would it become more pronounced as raising RPM mask it?
Sunny–
The original message included these comments:
matches your description. I wasn’t gonna worry much about that until I
cleaned the t/body at least.
