[x300] X300 Mystery

X300
1

Every 6 months or so I’m delighted to receive a car that many
have ‘had a go at’ but not quite managed to fix. Unsure whether
this makes me the ultimate trouble shooter or simply the last
resort, I just carry on regardless!

The latest problem is a really interesting and I haven’t solved it
yet. As you would guess, I’ve checked through many basic and not so
basic things which I won’t list here, there are too many, but
please don’t be offended if suggesting something I’ve already done .

X300 4.0 150k miles

The Symptoms;

The engine will start immedialtely from 12 hr. cold and run on 6
cylinders for about 40 secs.

After that, it will stumble and drop onto 3 cyl.s only, the exhaust
wreaking of petrol. It will misfire, backfire and the eventual
stall will see it refuse to start again. After 12 hrs. or so it
will start once more and the cycle is repeated. The Crank Sensor
has been replaced as step 1.

After very (very!) much ado, and checking for a blocked B1 Cat.
I’ve confirmed that B1 cylinder ign. coils (1,2 and 3) are not
firing after the initial 40 seconds running, although they still
have 12V supply on the white wires. Naturally, the swapping around
of coils and plugs etc. has been done. Coils 123 will run cyl.s
456 with no problems when moved, as will the plugs.

Trouble Codes = None. Pending or Latent Codes = None.
Compressions are 160-170 psi on all 6.

STFT’s when running are on + 24.2%. Both B1 and B2 02’s are
flatlining at 0V, the TPS is working fine, as is the Air Mass
meter. No air leaks are present, smoke machine confirmed. B1 fuel
injectors are working and all 3 cylinders are inducting air.

At close of play today I have pulled the ECU (no water damage) and
will try that on another properly runnning car on Monday to see
what it does. I can accept that the ECU may be failing to fire
(earth out) one coil, but why would it fail to fire 3 in one bank?

This brings me to my question, I’m hoping someone will know the
answer as I suddenly realised I don’t. Are X300 coils fired truly
sequentially, or are they fired as a group of 3 with a wasted
spark?

I have the wiring diagram. The fact that all 6 coils have
individual green negative wires with different trace colours
suggests they are fired sequentially, but it is possible that
within the ECU, those 3 wires for one bank all go to the same
place, and that could explain the dead 3 coils.

All of this makes me wonder if the ECU actually shuts down a bank
of 3 cylinders if it see something it does not like? I’ve always
beleived X300’s not to have the ‘cylinder shutdown’ that Merc.s
have, but maybe they do, and it does so 3 cyl,s at a time but just
never been seen before??

Regards

Steve

I do like a challenge…–
Jags on gas
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2

In reply to a message from Jags on gas sent Fri 5 Apr 2013:

That’s a sticky one Steve.
Not being proficiant on X300’s I would still hazard a guess that
all these syptomds lead to the ECM
As for sequential firing, I thought that was only introdiuced on
the later AJ16’s…is this an AJ6?
Because if I remember, the Aj6 and early 16’s used a similar set up
to the Rover 3500’s that fired their injectors in banks.
Could be totally barking up the wrong tree…or just barking ;o)=)

For it to behave perfectly at start up, negates any problems with
the cold start up circuits…after 40 mins, the engine is up to
operating temps.
Are there MAP (Mean Air Pressure) and IAT (Inlet Air Temperature)
sensors on these?
Would these be related to this symptom at all?
Perhaps they are totally divorced systems?
For three coils to drop out it’s obvious they are not getting the
required signal to fire but why??

From what you have said, it doesn’t seem to be the famous X300 ECM
malody.

Cheers,
Maximus–
The original message included these comments:

Every 6 months or so I’m delighted to receive a car that many
have ‘had a go at’ but not quite managed to fix. Unsure whether
this makes me the ultimate trouble shooter or simply the last
resort, I just carry on regardless!
The engine will start immedialtely from 12 hr. cold and run on 6
cylinders for about 40 secs.
After very (very!) much ado, and checking for a blocked B1 Cat.
I’ve confirmed that B1 cylinder ign. coils (1,2 and 3) are not
firing after the initial 40 seconds running, although they still
have 12V supply on the white wires. Naturally, the swapping around
of coils and plugs etc. has been done. Coils 123 will run cyl.s

–
Max Heazlewood '98XJ8http://www.pbase.com/padme002/jj_jag_1
Tasmania, Australia
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3

In reply to a message from Exjay8 sent Sat 6 Apr 2013:

Max,

Yes, X300 AJ16 4.0.

The engine drops onto 3 cylinders after 40 sec.s or so, not 40
mins. This would represent cold start enrichment duration I guess,
but I doubt whether the 02’s would be hot enough for closed loop
after just 40 sec.s, so maybe the engine is run open loop from a
base map until the 02’s come online.

It is easy to get the injector firing strategy that I normally deal
with mixed up with the coil firing strategy, the two don’t have to
be the same and it may be that they are not, so the question
remains for now, are the ignition coils fired sequentially, or as a
group?

In some ways it doesn’t matter for the moment, events have taken
another turn. The suspenese gnawed at me, so I came to work this
Saturday morning (normally doesn’t happen) and plugged the suspect
ECU into another car that runs perfectly. It still runs perfectly
with that ECU fitted. It is unlikely that there’s any fault in the
suspect ECU’s coil firing dept. at least.

Back to the thinking cap…

Regards

Steve–
The original message included these comments:

As for sequential firing, I thought that was only introdiuced on
the later AJ16’s…is this an AJ6?
Because if I remember, the Aj6 and early 16’s used a similar set up
to the Rover 3500’s that fired their injectors in banks.

–
Jags on gas
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4

In reply to a message from Jags on gas sent Sat 6 Apr 2013:

So, the ECU works perfectly in another car. The bank 1 coils
work perfectly in bank 2.

Have you tried swapping the injectors between bank 1 and
bank 2? The ‘‘cold start enrichment’’ symptom does suggest a
fueling problem, not an ignition problem.

I suspect you’re looking at a wiring fault, probably due to
corrosion but swapping the injectors just to eliminate them
as a suspect might not be a bad idea.–
The original message included these comments:

In some ways it doesn’t matter for the moment, events have taken
another turn. The suspenese gnawed at me, so I came to work this
Saturday morning (normally doesn’t happen) and plugged the suspect
ECU into another car that runs perfectly. It still runs perfectly
with that ECU fitted. It is unlikely that there’s any fault in the
suspect ECU’s coil firing dept. at least.

–
02 VDP – Driveway’s got too many SAABs in it!
Tampa Fl, United States
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5

In reply to a message from Exjay8 sent Sat 6 Apr 2013:

Max,

Yes, X300 AJ16 4.0.

The engine drops onto 3 cylinders after 40 sec.s or so, not 40
mins. This would represent cold start enrichment duration I guess,
but I doubt whether the 02’s would be hot enough for closed loop
after just 40 sec.s, so maybe the engine is run open loop from a
base map until the 02’s come online.

It is easy to get the injector firing strategy that I normally deal
with mixed up with the coil firing strategy, the two don’t have to
be the same and it may be that they are not, so the question
remains for now, are the ignition coils fired sequentially, or as a
group?

Er, wouldn’t firing the ignition coils in a group defeat the whole point
of having individual coils? Also, I don’t know if you can fire a group
of three simultaneously. One of them would fire on the intake stroke.

The injectors probably fire in batches of three though, I don’t know if
it’s a Motronic or derivative system but that’s what they apparently do.

One other thing that affects three and three cylinders are the knock
sensors. I don’t know how easy they are to swap around, and whether a
defective one could keep that bank from firing.On 06.04.2013 11:04, Jags on gas wrote:

–
Roy G. Ovrebo '98 Jaguar XJ8 3.2
Karmoy '82 BMW 732i
Norway

6

In reply to a message from Roy G. Ovrebo sent Sat 6 Apr 2013:

First, I am sure there is no wated spark in a X-300, nor would
there be any reasonable way to fire thee at once in a 6 cylinder.

You said you have the 12 volts when this event occurs. What is the
earth side going back to the ecu doing? You could parallel a test
light to ground if you do not have a scope.

Your trims are consistent with no firing, since all the O2 is still
in the mixture.

If there was some Jaguar ‘‘magic’’ shutting down the spark SURELY
they would kill the fuel as well, so I seriously doubt that is the
story.

Keep us posted!–
Ross - 89 XJS, 98 XJR, 99 XJR, 02 XJ8
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7

In reply to a message from Win sent Sat 6 Apr 2013:

Win,

Yes, the ECU runs another car without fault. Great idea in the
injectors. I did pull the rail and check the seals early on, and
then used another way of ruling dead injectors out. The car is one
we converted to run on LPG 110k miles ago. Using some simple wiring
trickery I ran the engine’s B2 on petrol and B1 on LPG, or rather I
didn’t, because even on the other fuel, cylinders 123 do not run.

That’s when I rigged a spare coil with a plug taped into it,
earthing the plug with a jump lead, then plugging in the 123 coil
wiring harnesses in turn to see if there was a spark. No sparks on
123 (but it did give a spark on 456) which took me down the ECU
path. up to now, you know how that ended!

Regards and Thanks

Steve–
The original message included these comments:

So, the ECU works perfectly in another car. The bank 1 coils
work perfectly in bank 2.
Have you tried swapping the injectors between bank 1 and
bank 2? The ‘‘cold start enrichment’’ symptom does suggest a
fueling problem, not an ignition problem.

–
Jags on gas
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8

In reply to a message from sparkenzap sent Sat 6 Apr 2013:

Ross,

The coil firing strategy is simply something I suddenly realised I
didn’t know, and I’ve never had to. With such an awkward problem I
tend to throw ideas at it and develop the theory until it can be
proved or disproved. I just wondered why and how 3 coils on one
bank could not be firing, unless they had a common driver in the
ECU which had died.

For 3 coils not to fire when they have 3 seperate earth wires (and
are presumably fired sequentially, with their own discrete drivers)
seems unbeleivable. Still, the idea is completely irrelevant now
that the ECU runs another car just fine, no dead drivers in there
however they fire the coils.

The other damning thing about all this is that the engine runs on 6
cyl.s for those first 40 cold seconds, showing all ign. and
injection components to be working for that time. Why not
afterward??

On Monday I will check out the coil wiring from the pin-out to the
coils and will rig a test lamp too, just to see if they are being
earthed, in spite of my lash-up coil spark tester showing that they
are not. Always best to check and confirm things from 2
perspectives. Then it’ll be both temp. sensors that get swapped
around (coolant and air).

I’ve never heard of any cylinder shut-down measure on any Jaguar
model at all, even Merc.s will switch a disabled cylinder back on
after a restart (this car does not!) but standing there listening
to it cut 3 cylinders after just 40 sec.s almost has me beleive it
could be true!

And yes, I agree that the STFT’s suggest no coil/plug firing in any
meaningful way on those cylinders at least.

Latest shot in the dark;

Has the front pulley broken up in some way, making the rotor run
eccentric, thus missing the Crank sensor on 123’s patch?

On Monday, I’ll find out.

Regards and Thanks

Steve–
Jags on gas
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9

In reply to a message from Roy G. Ovrebo sent Sat 6 Apr 2013:

Roy,

Part of the reason for having 6 individual coils is to allow them
more time to charge properly and release more energy when it’s
their turn to fire. They also run a little cooler than one coil
firing 6 plugs would, as on the XJ40. Knowing that is part of what
put me off the trail I guess, having 6 coils does not indicate
sequent firing per se.

Certainly the X300 injectors are fired as a half-group, 3 and 3,
but the later X308 injectors are fired in sequence. It doesn’t
follow that the coils are fired the same way as the injectors on
any engine though, not just taking it for granted I mean.

Still, what the coil firing strategy is used was a question which
just popped up, but I’m sure you and Ross are right, wasted spark
would not work on a 6, so it must be sequent.

And the ECU isn’t broken either…Dammit!

More thought required!

Regards and Thanks

Steve–
The original message included these comments:

Er, wouldn’t firing the ignition coils in a group defeat the whole point
of having individual coils? Also, I don’t know if you can fire a group
of three simultaneously. One of them would fire on the intake stroke.
The injectors probably fire in batches of three though, I don’t know if

–
Jags on gas
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10

In reply to a message from Jags on gas sent Sat 6 Apr 2013:

Ah my mistake steve ;o)
Being in the 40 sec range, would it still have anything to do with
peripheral sensors involved?
Are the O2 sensors on an X300 heated?
Are you familiar with Gunson’s Colour Tune?
Perhaps you could employ this to look at the ‘dead’ cyclinders.
Perhaps you could ascertain the condition of the harmonic balancer
with a timing strobe?
You are definate that it’s ignition that drops out?

The advancements for the X308 over the X300 was huge and employs a
completely reworked stratergy for sequential firing of both
ignition and injectors.

Onwards and upwards ;o)

Cheers,
Maximus–
The original message included these comments:

Certainly the X300 injectors are fired as a half-group, 3 and 3,
but the later X308 injectors are fired in sequence. It doesn’t
follow that the coils are fired the same way as the injectors on
any engine though, not just taking it for granted I mean.
Still, what the coil firing strategy is used was a question which
just popped up, but I’m sure you and Ross are right, wasted spark
would not work on a 6, so it must be sequent.
And the ECU isn’t broken either…Dammit!
More thought required!
Regards and Thanks
Steve

–
Max Heazlewood '98XJ8http://www.pbase.com/padme002/jj_jag_1
Tasmania, Australia
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11

In reply to a message from Exjay8 sent Sat 6 Apr 2013:

Thanks Max,

I’ll beat it sometime, but it’s a hard road, especially with this
one. I’ve been in (yes I know it’s Sunday!) and swapped both of the
temp. sensors from a good car. 10 mins will see the ECU refitted
and we’ll see what that brings. At least I don’t have an owner
breathing down my neck, I gave him a courtesy car to give me chance
to think freely.

I’ll check the pulley as you say, but I doubt the theory now as 123
are not next to each other (across 2 crank RPM) in the firing
order. I’m going to re-confirm that it is the ign. that drops out
(for the 3rd time!) just for purity, stop me going off the wrong
way.

It’s an ill wind that blows nobody any good. At least I’ve now
(finally) got a picture showing how to easily remove the security
screws on the ECU cage and have remembered to describe an easy
technique for identifying dead cylinders that I’ve been using for
many years. Take off the tin cover from the manifolds. Run the
engine and see which manifolds have hot spots (IR thermometer is
best but fingers will do!) and which do not.

Guess the results on this one? 123 get a little warm during the 40
sec.s, but then go cold. 456 continue to get hotter and fingers are
not the tool for checking those any longer!

The 02’s are 4 wire so they are heated, and even if the heater
circuit were off (no codes shown) then at some point they’d get hot
enough to work on their own, not at idle RPM perhaps, but at xxx
RPM. I lost my Colourtune perhaps to someone’s pocket years ago,
unless its still running as a plug in a car somewhere?? Still, not
a great deal of use down the tunnel and with a coil fitted on top I
guess.

Latest ‘off the wall idea’…

Could some piece of Debris be inducted and go up the branch to 123,
partially blocking it enough to cut the airflow to a point where
combustion is unsustainable? That would still see all compressions
good, it would still suck at the fuel regulator vacumn take-off
like it does, it would still inject fuel like it does etc. etc.
But would it still then spark coils 123?

Hmmm!

I doubt the changing of both temp. sensors will see any useful
results, I’ve only done it for completness. At least leaving the
ECU off for 24hrs constitutes a hard reset. I might risk fitting
the ECU from the good car to this one, although I don’t normally do
that in case a wiring fault fries a second ECU. Better to fit the
suspect one to a good car and then prove/disprove.

It may be time to remove the throttle body and get the borescope to
work. But not today!

Regards and Thanks

Steve–
The original message included these comments:

Being in the 40 sec range, would it still have anything to do with
peripheral sensors involved?
Are the O2 sensors on an X300 heated?
Are you familiar with Gunson’s Colour Tune?
Perhaps you could employ this to look at the ‘dead’ cyclinders.
Perhaps you could ascertain the condition of the harmonic balancer
with a timing strobe?
You are definate that it’s ignition that drops out?
The advancements for the X308 over the X300 was huge and employs a
completely reworked stratergy for sequential firing of both
ignition and injectors.

–
Jags on gas
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12

In reply to a message from Jags on gas sent Sun 7 Apr 2013:

Steve:
I sure do not have the answer to your riddle, but my take on
the theories so far…

The pulley theory is a non starter, since the absolute
position is not measured, but rather the pulse count after
the missing tooth. It would be a robust control algorithm
indeed that could recover from a group of missing pulses.

I have a hard time believing that any deliberate control
strategy would shut down a bank firing- especially without
shutting off the fuel. That would be a fire hazard and a
catalyst killer.

So, I believe you are going to find something you missed in
your original pass, like a low or high input voltage to the
ecu (it has several), a flaky ground, or an ecu connector
problem. Remember, electrical circuits are not perfect.
Something out of range enough to disturb one bank from
working, might not affect the other.

Did you try putting the known good ecu in the subject car?

Good luck!–
Ross - 89 XJS, 98 XJR, 99 XJR, 02 XJ8
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13

In reply to a message from sparkenzap sent Sun 7 Apr 2013:

Thanks Ross,

I bit the bullet, broke a rule and fitted the known good ECU to the
bad car…No dice, no difference, and that includes the swapped
temp. sensors as well. At least I can forget them now, I always
view a whole list of things tried and then ruled out as a positive
thing, not a list of failures.

I think you are right. The problem is likely something I’ve touched
on already but not been diligent enough.

Here’s the latest ‘off the wall’ idea;

We know that cyl.s 123 injectors are fired as a group. What if
those injectors were all earthed out for 100% of the time the
engine is running by some kind of short circuit?

My guess would be a car that wreaks of petrol, 3 cylinders that
flood and won’t run, backfiring due to overfulleing etc. etc.

This I will follow up!

Thanks and Regards

Steve–
The original message included these comments:

So, I believe you are going to find something you missed in
your original pass, like a low or high input voltage to the
ecu (it has several), a flaky ground, or an ecu connector
problem. Remember, electrical circuits are not perfect.
Something out of range enough to disturb one bank from
working, might not affect the other.
Did you try putting the known good ecu in the subject car?

–
Jags on gas
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14

In reply to a message from Jags on gas sent Sun 7 Apr 2013:

‘‘We know that cyl.s 123 injectors are fired as a group. What if
those injectors were all earthed out for 100% of the time the
engine is running by some kind of short circuit?’’

I like that! Or something like it. The short could cause the
flood of gas AND shunt enough current to keep the coils from firing.

Or, something completey different, heh!–
Ross - 89 XJS, 98 XJR, 99 XJR, 02 XJ8
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15

In reply to a message from sparkenzap sent Sun 7 Apr 2013:

Have you guys ever tried those noid devices you connect to the
wiring for each injector and they givew signals as to functionality?
Maybe that’s an easy way of tracking down any abnormalities??

Cheers,
Maximus–
The original message included these comments:

‘‘We know that cyl.s 123 injectors are fired as a group. What if
those injectors were all earthed out for 100% of the time the
engine is running by some kind of short circuit?’’
I like that! Or something like it. The short could cause the
flood of gas AND shunt enough current to keep the coils from firing.
Or, something completey different, heh!
Ross - 89 XJS, 98 XJR, 99 XJR, 02 XJ8

–
Max Heazlewood '98XJ8http://www.pbase.com/padme002/jj_jag_1
Tasmania, Australia
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16

In reply to a message from Exjay8 sent Sun 7 Apr 2013:

I think I’d ignore the fuelling and concentrate on the loss of
spark.–
Dave Collishaw '79 Daimler Sovereign '96 X305 '56 BSA A10
Cambridgeshire, United Kingdom
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17

In reply to a message from sparx sent Sun 7 Apr 2013:

Yes, that would be perfectly fine if it has been made a certainty
that it is the ignition at fault.
Quite often, one can mask the other.

Cheers,
Maximus–
The original message included these comments:

I think I’d ignore the fuelling and concentrate on the loss of
spark.
Dave Collishaw '79 Daimler Sovereign '96 X305 '56 BSA A10
Cambridgeshire, United Kingdom

–
Max Heazlewood '98XJ8http://www.pbase.com/padme002/jj_jag_1
Tasmania, Australia
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18

In reply to a message from sparx sent Sun 7 Apr 2013:

Yes Dave and Max,

Today, if I get nothing else done on it I will refit the ECU and
check once more (3rd time) that there are no little blue flashes of
joy.

A week on (part time) and still nothing really adds up…What fun!
Still, it’s only a car, man made it and man can fix it.

Ross,

You are almost describing the kind of cylinder disablement facility
I was thinking of? Whether Jaguar designed that to happen or not I
don’t know, but if it does, I guess it doesn’t matter 'cos the
result is the same! Still, it remains to be seen if that theory is
worth anything or not. We’ll get there, I’m just ot sure how yet.

One other thing I might do;

Disconnect both 02’s on my good car just to see what happens. On
the broken one they both flatline at 0V. I have had a car brought
here still runnning on no 02’s at all in the past, but it does not
mean that all X300’s will do that.

Regards and Thanks

Steve–
The original message included these comments:

In reply to a message from Exjay8 sent Sun 7 Apr 2013:
I think I’d ignore the fuelling and concentrate on the loss of
spark.

–
Jags on gas
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19

In reply to a message from Jags on gas sent Mon 8 Apr 2013:

Latest update;

Original ECU refitted. Engine started on 5 or 6 cyl.s first time.
Drops to cylinders 456 only after 40 sec.s or so, front manifold
only slightly warm but not getting hotter. No spark on 123. Test
rig has been checked on cyl.4 and sparks just fine.

So near, yet so far…

Regards

Steve–
Jags on gas
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20

Steve, I have just got back from holiday so I have missed all this. As
you mentioned that the car has been worked on by many people, could it
be that that are now two problems compounded by someone inadvertently
swapping the O2 connections over? They are, after all, bank related.

HTH
Chris C

Jags on gas wrote:> In reply to a message from sparx sent Sun 7 Apr 2013:

Yes Dave and Max,

Today, if I get nothing else done on it I will refit the ECU and
check once more (3rd time) that there are no little blue flashes of
joy.

A week on (part time) and still nothing really adds up…What fun!
Still, it’s only a car, man made it and man can fix it.

Ross,

You are almost describing the kind of cylinder disablement facility
I was thinking of? Whether Jaguar designed that to happen or not I
don’t know, but if it does, I guess it doesn’t matter 'cos the
result is the same! Still, it remains to be seen if that theory is
worth anything or not. We’ll get there, I’m just ot sure how yet.

One other thing I might do;

Disconnect both 02’s on my good car just to see what happens. On
the broken one they both flatline at 0V. I have had a car brought
here still runnning on no 02’s at all in the past, but it does not
mean that all X300’s will do that.

Regards and Thanks

Steve

The original message included these comments:

In reply to a message from Exjay8 sent Sun 7 Apr 2013:
I think I’d ignore the fuelling and concentrate on the loss of
spark.

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