[E-Type] My Bucking Bronco Mystery

About a month ago I was cruising along at about 50 mph
when very suddenly the car started violently bucking and
backfiring. I turned around and headed home, but by the
time I got there it was running fine. Just before I had
washed the car, including the engine and suspension area,
so I attributed it to water getting somewhere where it
wasn’t supposed to be. Until this morning. Exactly the
same scenario, even exactly the same place! Weird.

The onset is sudden and violent. It is not RPM related,
i.e. the bucking and backfiring occur at any RPMs. It
idles fine, but occurs with any attempt to accelerate,
however gently. I do not think it is fuel related. Fuel
issues can result in rough running, but not this violent,
accompanied by backfiring. It is as though the ignition
is being switched on and off rapidly. After a couple of
minutes the frequency of the misfiring gradually
decreases, and after about 5 minutes the car is running
smooth as silk. The ambient temperature was about 50
degrees during the first incident, about 80 degrees today.

In the interest of full disclosure, I have had Ray’s EDIS
installed for several years, never a problem. I hate
intermittent problems. If the symptoms had persisted I am
sure I could have diagnosed the problem, but now with no
existing symptoms much more difficult.

Cheers,
Rod–
67 OTS, 55 MGTF
Quechee/VT, United States
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In reply to a message from Rod Fisher sent Fri 17 Jun 2016:

Rod,

The time I had that symptom, it turned out to be – surprise
surprise – the ignition switch plus an especially heavy ke
key ring. Worth a check.

Jerry–
Jerry Mouton '64 FHC 889791 ‘MIK Jaguar’
Palo Alto, California, United States
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Pistons in the carbs sticking? Dirt in the fuel valve in the carbs
generating in flooding or starvation?On Fri, Jun 17, 2016 at 11:45 AM, Rod Fisher rodfisher@mac.com wrote:

About a month ago I was cruising along at about 50 mph
when very suddenly the car started violently bucking and
backfiring. I turned around and headed home, but by the
time I got there it was running fine. Just before I had
washed the car, including the engine and suspension area,
so I attributed it to water getting somewhere where it
wasn’t supposed to be. Until this morning. Exactly the
same scenario, even exactly the same place! Weird.

The onset is sudden and violent. It is not RPM related,
i.e. the bucking and backfiring occur at any RPMs. It
idles fine, but occurs with any attempt to accelerate,
however gently. I do not think it is fuel related. Fuel
issues can result in rough running, but not this violent,
accompanied by backfiring. It is as though the ignition
is being switched on and off rapidly. After a couple of
minutes the frequency of the misfiring gradually
decreases, and after about 5 minutes the car is running
smooth as silk. The ambient temperature was about 50
degrees during the first incident, about 80 degrees today.

In the interest of full disclosure, I have had Ray’s EDIS
installed for several years, never a problem. I hate
intermittent problems. If the symptoms had persisted I am
sure I could have diagnosed the problem, but now with no
existing symptoms much more difficult.

Cheers,
Rod

67 OTS, 55 MGTF
Quechee/VT, United States
–Posted using Jag-lovers JagFORUM [forums.jag-lovers.org]–


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Les…'68 S1.5 2+2


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When was the last time you put oil in the carb chamber?
LLoyd----- Original Message -----
About a month ago I was cruising along at about 50 mph
when very suddenly the car started violently bucking and
backfiring. I turned around and headed home, but by the
time I got there …


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In reply to a message from Rod Fisher sent Fri 17 Jun 2016:

It definitely sounds electrical in nature. As stated, check
the ignition switch and your high-tension wires. You might
have an intermittent arcing in the plug leads. I once had a
similar problem that was only found by accident when the
arcing could be seen in the dark with the engine running.
(but have a priest exorcise the area where driving just to
cover all the bases).–
The original message included these comments:

wasn’t supposed to be. Until this morning. Exactly the
same scenario, even exactly the same place! Weird.


Tom Hishon, 69 E-type 2+2, 69 E-type OTS, 85 XJ6, '03 X-type
Wasilla, Alaska, United States
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In reply to a message from Rod Fisher sent Fri 17 Jun 2016:

Hi Rod, if your ignition is conventional with points and
condenser, this thread might of interest to you.

http://forums.jag-lovers.org/av.php?1759948p69

Good luck
Anthony–
The original message included these comments:

About a month ago I was cruising along at about 50 mph
when very suddenly the car started violently bucking and
backfiring. I turned around and headed home, but by the


Anthony, Toronto Ontario, 69 OTS
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In reply to a message from Rod Fisher sent Fri 17 Jun 2016:

I agree . It is an electrical problem. I had a similar problem
with my '53 100-4 Healey . Try new plugs and check the ht
wires , but likely, you will end up at the distributor .
After two years of a similar problem, I took out the
distributor and took it apart. After about half an hour, I
found a small steel washer (from the points) that was shorting
one plate to another intermittently. I wasn’t certain at
first, but after I removed that washer , it never happened
again. Your problem could be of a similar nature . One
must go over ALL the possibilities…methodically…
David Potter–
David Potter, '71 OTS E-Type 4.2
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Sounds like ignition to me too but with Ray’s system not likely.
Possibly a sticking float? I had a sank float once, it ran pretty
good until engine got mostly warmed up, then it bucked and snorted.
Never really understood why 1 sunk float out of 3 could make the
engine act so violently. Like you describe it acted like someone was
shutting off the ignition then back on. It has been so many years ago
I don’t recall how the return trip home went. I don’t recall it
bucking all the way back to the garage or feeling that I wasn’t going
to make it.
pauls

About a month ago I was cruising along at about 50 mph
when very suddenly the car started violently bucking and
backfiring. I turned around and headed home, but by the
time I got there it was running fine. Just before I had
washed the car, including the engine and suspension area,
so I attributed it to water getting somewhere where it
wasn’t supposed to be. Until this morning. Exactly the
same scenario, even exactly the same place! Weird.

The onset is sudden and violent. It is not RPM related,
i.e. the bucking and backfiring occur at any RPMs. It
idles fine, but occurs with any attempt to accelerate,
however gently. I do not think it is fuel related. Fuel
issues can result in rough running, but not this violent,
accompanied by backfiring. It is as though the ignition
is being switched on and off rapidly. After a couple of
minutes the frequency of the misfiring gradually
decreases, and after about 5 minutes the car is running
smooth as silk. The ambient temperature was about 50
degrees during the first incident, about 80 degrees today.

In the interest of full disclosure, I have had Ray’s EDIS
installed for several years, never a problem. I hate
intermittent problems. If the symptoms had persisted I am
sure I could have diagnosed the problem, but now with no
existing symptoms much more difficult.
<<<<<<<<<<<<From: “Rod Fisher” rodfisher@mac.com
Subject: [E-Type] My Bucking Bronco Mystery


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In reply to a message from Paul Spurlock sent Fri 17 Jun 2016:

Thanks Paul, I missed Rod’s EDIS comment!
Anthony–
The original message included these comments:

Sounds like ignition to me too but with Ray’s system not likely.


Anthony, Toronto Ontario, 69 OTS
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In reply to a message from mouton sent Fri 17 Jun 2016:

Jerry,

I think the ignition switch is a good candidate. Not the
key ring though, only ignition key and boot key on the
ring.

I have trouble rationalizing the symptoms with fuel
issues. The very sudden onset while cruising at a steady
pace with light throttle, the frequency (every one or two
seconds) and the accompanying backfires seem to me to
point to electrical issues, but then I have been known to
be wrong, as my wife frequently reminds me :slight_smile:

Rod–
The original message included these comments:

The time I had that symptom, it turned out to be – surprise
surprise – the ignition switch plus an especially heavy ke
key ring. Worth a check.


67 OTS, 55 MGTF
Quechee/VT, United States
–Posted using Jag-lovers JagFORUM [forums.jag-lovers.org]–


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In reply to a message from Rod Fisher sent Fri 17 Jun 2016:

If you think.it could be the ignition switch, bock.up.a
small bulb or volt.meter and.see.what happens.when it
bucks.–
Mike Oldak 67 1 1/4 OTS
Bethesda, Maryland, United States
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In reply to a message from mike o sent Fri 17 Jun 2016:

I would substitute a coil.
Years ago I had a bad coil that only acted u when warm–
Dennis Vancouver Canada 69 Roadster
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I must admit the ign sw. is definitely a possibility, mine failed with
the same symptom, engine quit for like a second big backfire pulled
strong then quit again with the same recovery. For some reason I
instinctively grabbed the ign. key, it didn’t do it again that day…
I did not turn around and go home. Next day or so I disassembled,
cleaned and lubed the sw. never had another problem. One symptom of a
sw. possibly ready to give problems is heat, if its hot after driving
a short while it has high resistance and that’s going to lead to
trouble. Back to the OP my failing ign sw was definitely an on/off
scenario whereas my sank float was serious bucking but did not feel
like the engine completely shut down, it never quit running but acted
like it lost 4 cylinders suddenly.
pauls

Jerry,

I think the ignition switch is a good candidate. Not the
key ring though, only ignition key and boot key on the
ring.

I have trouble rationalizing the symptoms with fuel
issues. The very sudden onset while cruising at a steady
pace with light throttle, the frequency (every one or two
seconds) and the accompanying backfires seem to me to
point to electrical issues, but then I have been known to
be wrong, as my wife frequently reminds me :slight_smile:
<<<<<<<<<<From: “Rod Fisher” rodfisher@mac.com
Subject: Re: [E-Type] My Bucking Bronco Mystery


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