[E-Type] S1 E-Type 4.2 Misses When Warm

Got the S1 E running but it misses when warmed up. I have not
driven it yet. It starts well and idles fine when cold but as the
temp increases to normal the miss gets worse until it begins to
want to die completely unless I raise the idle speed quite a bit.
The miss is present at all RPM. The carbs have not been rebuilt
but float bowls were cleaned out and new standard needle & seats
were installed. Jets & needles were cleaned w carb cleaner and
blown out with compressed air. This miss situation sounds like
ignition to me. It has a new Pertronix in the dizzy and I suspect
the coil or wires (unchanged). Plugs (N11Y) are new and dizzy cap
and rotor look good and show no signs of extended use. The wires
have the Champion ends which I have heard can be problematic.
Messing with timing and carb adjustment changes nothing as does any
level of choke. I have a V12 coil - is it interchangable with an
XK coil for testing purposes? Am I on the right track?
Thanks… Bill–
XK150 FHC, S1 OTS, S3 OTS, S3 2+2
Phoenix AZ, United States
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In reply to a message from Bill Franklin sent Sun 20 Aug 2006:

Could be a lot of things Bill.
I always like to go back and check the last few things I touched.

  1. How about checking the firing order versus wire position in the
    cap? 2. Some aftermarket rotors have caused problems. 3. Is your
    diz shaft tight in the bushings? Air gap isn’t supercritical on the
    Pertronix but a combination of tolerances might cause problems. If
    you have a dwell meter you can check. Shouldn’t waiver more than a
    degree or two. 4. After that, any ignition component (plugs/caps
    wires/diz cap/rotor/coil/wires. 5. I don’t know if the 12 cyl coil
    can work on a 6.

Dave–
1969 BRG OTS
Skaneateles, NY, United States
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In reply to a message from Bill Franklin sent Sun 20 Aug 2006:

Bill,

I think you are on the right track. Lucas coils get old and,
whether used or not, tend to ark internally which is
exacerbated by heat. I have found that when my Jag starts to
sputte/miss when the engine is hot, a new coil is the
ticket. I finally gave up on Lucas coils altogether and went
with a Flamethrower. I haven’t had a problem since.

The V-12 coil is for a ballasted ignition and not right for
S1 E-types. Running a ballasted coil on a non-ballasted
system will eventually burn the coil up and probably the
points/condenser with it.

New coils are not that expensive but give you a wealth of
security. Same thing with your ignition wires and plug ends.
Go ahead and change them out if you are not sure of their age.

Richard Liggitt–
The original message included these comments:

Got the S1 E running but it misses when warmed up. I have not
driven it yet. It starts well and idles fine when cold but as the
temp increases to normal the miss gets worse until it begins to
want to die completely unless I raise the idle speed quite a bit.
The miss is present at all RPM. The carbs have not been rebuilt
but float bowls were cleaned out and new standard needle & seats
were installed. Jets & needles were cleaned w carb cleaner and
blown out with compressed air. This miss situation sounds like
ignition to me. It has a new Pertronix in the dizzy and I suspect
the coil or wires (unchanged). Plugs (N11Y) are new and dizzy cap
and rotor look good and show no signs of extended use. The wires


'70 E Roadster 1R11998, '98 XK8 Roadster, www.XKEBooks.com
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In reply to a message from Richard L. sent Tue 22 Aug 2006:

So everyone can know the outcome… I tested and found high
resistances in the distributor cap, Champion pug ends and Lucas
coil. Replaced with new distributor cap and rotor, Magnacor wires
and Pertronix coil (Pertronix in dizzy)… and, the miss is gone.
Unfortunately couldn’t adjust the carbs to achieve the correct tune
(too rich) so I’ll be digging into them shortly.>In reply to a message from Bill Franklin sent Sun 20 Aug 2006:

Bill,

I think you are on the right track. Lucas coils get old and,
whether used or not, tend to ark internally which is
exacerbated by heat. I have found that when my Jag starts to
sputte/miss when the engine is hot, a new coil is the
ticket. I finally gave up on Lucas coils altogether and went
with a Flamethrower. I haven’t had a problem since.

The V-12 coil is for a ballasted ignition and not right for
S1 E-types. Running a ballasted coil on a non-ballasted
system will eventually burn the coil up and probably the
points/condenser with it.

New coils are not that expensive but give you a wealth of
security. Same thing with your ignition wires and plug ends.
Go ahead and change them out if you are not sure of their age.

Richard Liggitt

The original message included these comments:
Got the S1 E running but it misses when warmed up. I have not
driven it yet. It starts well and idles fine when cold but as the
temp increases to normal the miss gets worse until it begins to
want to die completely unless I raise the idle speed quite a bit.
The miss is present at all RPM. The carbs have not been rebuilt
but float bowls were cleaned out and new standard needle & seats
were installed. Jets & needles were cleaned w carb cleaner and
blown out with compressed air. This miss situation sounds like
ignition to me. It has a new Pertronix in the dizzy and I suspect
the coil or wires (unchanged). Plugs (N11Y) are new and dizzy cap
and rotor look good and show no signs of extended use. The wires


XK150 FHC, S1 OTS, S3 OTS, S3 2+2
Phoenix AZ, United States
–Posted using Jag-lovers JagFORUM [forums.jag-lovers.org]–

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