[v12-engine] High RPM stumble?

In my quest to find a good XJ-S I drove another one today. It is an '86 model year that has been idle for five years. It idles well and runs well at lower RPMs. When I accelerated it on the freeway it would stumble at about 4000 RPMs. It didn’t die but it had a lot of trouble getting past the 4000 mark. Can anyone shed any light on what may be causing this problem?

Thanks for the help.

Best regards,
Tom_________________________________________________________________
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In reply to a message from tom white sent Thu 27 Sep 2007:

Hi , did you try some fresh gas.Art–
The original message included these comments:

In my quest to find a good XJ-S I drove another one today. It is an '86 model year that has been idle for five years. It idles well and runs well at lower RPMs. When I accelerated it on the freeway it would stumble at about 4000 RPMs. It didn’t die but it had a lot of trouble getting past the 4000 mark. Can anyone shed any light on what may be causing this problem?


Pacific Jaguar Enthusiasts Group 44, Canada.
Pitt Meadows, BC, Canada
–Posted using Jag-lovers JagFORUM [forums.jag-lovers.org]–
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Tom

That could be the secondary coil at fault. There is a ducelier single coil
as a direct replacement. A quick search will give you the part number.

Kevin
Brisbane QLD
Australia
74 XJ12L “Ted”
83 XJS “Carmel”
83 XJS “Joanna”-----Original Message-----
From: tom white
Subject: [v12-engine] High RPM stumble?

In my quest to find a good XJ-S I drove another one today. It is an '86
model year that has been idle for five years. It idles well and runs well at
lower RPMs. When I accelerated it on the freeway it would stumble at about
4000 RPMs. It didn’t die but it had a lot of trouble getting past the 4000
mark. Can anyone shed any light on what may be causing this problem?

Thanks for the help.

Best regards,
Tom

Visit the Jag Lovers homepage at http://www.jag-lovers.org for exciting services and resources including Photo Albums, Event Diary / Calendar, On Line Books and more !

A good possibility is that the front ignition coil (used only as a ballast) may be defective and/or disconnected from the rear ignition coil located in the “V”. I removed both coils in my '86, and replaced with a MSD 8207, see pics here:
http://www.jag-lovers.org/snaps/snap_view.php3?id=1145838596
Regards…Jim Kocmoud, 86 XJ-S, Chicago/Daytona----- Original Message ----
From: tom white tswhitez123@hotmail.com
To: v12-engine@jag-lovers.org
Sent: Wednesday, September 26, 2007 11:42:00 PM
Subject: [v12-engine] High RPM stumble?

In my quest to find a good XJ-S I drove another one today. It is an '86 model year that has been idle for five years. It idles well and runs well at lower RPMs. When I accelerated it on the freeway it would stumble at about 4000 RPMs. It didn’t die but it had a lot of trouble getting past the 4000 mark. !

Visit the Jag Lovers homepage at http://www.jag-lovers.org for exciting services and resources including Photo Albums, Event Diary / Calendar, On Line Books and more !

In reply to a message from tom white sent Thu 27 Sep 2007:

Tom,
Another possibility is the fuel filters are restricted. I have
found that a restricted filter will hold a certain speed but a few
minutes later the engine starts to ‘‘mess about’’. The cure is to
back off the gass slightly. This will work for awhile and as more
crud covers the restricted filter the speed keeps going down.
On my '92 the external filter has a filter screen that never gets
contaminated. This is because the in tank 70 and 400 micron filters
catch it first. his is followed by the pump inlet filter which is
finer yet. That one cost me a bundle to find this out.

Noel

My ''88 had 2 coils and it woked perfectly. But both must be in the
circuit to get high RPM, as others have stated.–
The original message included these comments:

In my quest to find a good XJ-S I drove another one today. It is an '86 model year that has been idle for five years. It idles well and runs well at lower RPMs. When I accelerated it on the freeway it would stumble at about 4000 RPMs. It didn’t die but it had a lot of trouble getting past the 4000 mark. Can anyone shed any light on what may be causing this problem?


'92 XJS Conv, '88 XJS Coupe, 1914 &1915 Ford T’s (Forguars)
Edmond, OK, United States
–Posted using Jag-lovers JagFORUM [forums.jag-lovers.org]–
–Support Jag-lovers - Donate at http://www.jag-lovers.org/donate04.php

Visit the Jag Lovers homepage at http://www.jag-lovers.org for exciting services and resources including Photo Albums, Event Diary / Calendar, On Line Books and more !