[xj-s] Fw: I'm Stumped!

Gentlemen,
I have a 92 XJS coupe with a V12/auto. From day one, I have noticed a
puffing from the exhaust tip on the passenger side…never can remember
which is A and which is B. I have also been chasing a FF44 code for 3 1/2
years now. Some may remember my previous posts regarding this. I just had my
injectors serviced and the results are wonderful…smoother and definitely
less fuel consumed however the passenger side is not running as smooth as
the drivers side for sure.
I have replaced:
cap, rotor (Marelli) plugs, wires
exhaust from downpipes to tips ( original equipment )
02 sensors
air cleaners
cleaned intakes
new vaccum hoses
new grommets for the linkage
injectors and fuel rail serviced to perfection
I am still seeing a FF44 code while the passenger side is puffing…similar
to a Vette I had in the past where you could “feel” every cylinder firing
through the exhaust.

Any suggestions would be welcomed…believe me.
I want to get this baby running like a V12 can hum. Any questions will be
answered.

Thanks in advance,
John Schmincke
Vail, Arizona

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In reply to a message from John Schmincke sent Wed 30 Jan 2008:

what you are describing is almost certianly a misfire. I see
you’ve done the best things to address this, but, you should try to
narrow down which cylinder is acting up.

Fuel: use a mechanic’s stethoscope (or a screwdriver) to listen to
each injector. Since these were recently cleaned, I doubt if the
injector is the problem, but, you may have a poorly seated
connector, or a short in the harness. A ‘noid’ as is commonly
found at the auto parts stores will let you plug into the harness
at each injector location and see that the fire signal is present.

Spark: an inductive pickup timing light, clamped over each plug
wire (that is, check each one this way) on the suspect bank, will
help to identifiy which plug is not getting fire from the coil.

It is possible to still have a bad plug, even with fire coming from
the coil. Only way I know to check this is to replace the plugs.

It is also common to find that one plug wire was not seated well
enough on either the plug or the cap.

Good luck!

Mike–
Mike, 1990 5.3 XJS Convertible, ‘Caterwaul’
Lakewood, OH, United States
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It is also possible that the spark is being delivered to somewhere other
than the spark plug. Listen carefully for a snapping sound, somewhat
like a valve with too much clearance. This is the spark happening
outside the combustion chamber. Look at the top of the engine in the
dark while idling, look for arcing along the ignition wires. I had a
cracked spark plug boot on my car that was allowing the spark to arc to
intake manifold; it was hard to find.

Good Luck,

Dave Harvey
89 XJ-S V12 Marelli
Los Angeles, Ca.

mike90 wrote:

In reply to a message from John Schmincke sent Wed 30 Jan 2008:

what you are describing is almost certianly a misfire. I see
you’ve done the best things to address this, but, you should try to
narrow down which cylinder is acting up.

Spark: an inductive pickup timing light, clamped over each plug
wire (that is, check each one this way) on the suspect bank, will
help to identifiy which plug is not getting fire from the coil.

It is possible to still have a bad plug, even with fire coming from
the coil. Only way I know to check this is to replace the plugs.

It is also common to find that one plug wire was not seated well
enough on either the plug or the cap.

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In reply to a message from Dave Harvey sent Wed 30 Jan 2008:

What everyone else said, plus a compression test is in order. but
before that I would unplug each injector while it is running on
that side to determine which cylinder is at fault, then inspect
injector and wires, spark plug and wire, and look inside the dizzy
cap for evidence of arcing.
Also, and I’m not saying this is likely, but possible…the Marelli
distributer is set so that the best average distance to each post
from the rotor is found through the advance range. Due to
this, ‘sometimes’ the spark finds an easier path to the next, or
previous cylinder causing a misfire. This usually presents itself
either at idle, or at higher revs, but not both. Tweaking the dizzy
1 or 2 degrees max in one direction or the other can sometimes fix
this. I think Roger bywater suggests turning the dizzy 2 degrees
clockwise, but check the archives on this. BTW This is one of about
10 reasons why I want to go distributer-less…

Dave
Atlanta–
Penfold99
Atlanta, GA, United States
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Penfold99 wrote:

…the Marelli distributer is set so that the best average
distance to each post from the rotor is found through the advance
range. Due to this, ‘sometimes’ the spark finds an easier path to the
next, or previous cylinder causing a misfire.

Or right through the side of the cap to one of the mounting screws.

…BTW This is one of about 10
reasons why I want to go distributer-less…

It’s also another good reason to go to the Lucas distributor with the
MSD Automatic Coil Selector. The mechanical advance mechanism in the
Lucas distributor keeps the rotor aligned better with the terminals
in the cap.

– Kirbert

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Hi Mike and thanks for your thoughts. The injectors are good as they were
just tested when serviced. I looked all over Tucson today for a noid light.
Found one for Bosch but can’t pick it up until Thursday. I am curious to
give it a try though. My injection harness looks pretty good for a 92 but a
wire could have been pinched somewhere over the years.

Spark: I’ll give this a try also if the noid light test doesn’t yield
anything. The 2 coils were replaced also within the last 7 months with new
original equipment. That also made a slight difference in making the engine
run smoother. My original coils were working fine as far as I know but had
that aged look. I still have them anyway.

Plugs are new. I am hoping they are okay but will change them out if needed.
Plug wires are seated properly both on the plugs and in the cap.

Good luck! You bet! I’ll post a fix when I find it and hope it helps someone
else down the road.

I suspect the FF44 is hinging on this.

John

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Hi Dave,

It is also possible that the spark is being delivered to somewhere other
than the spark plug.

I had that happen when I bought the car. Cracked boots causing sparks
jumping all over the place and as you say, only can be seen at night. Not
the case this time though.

I’ll post a fix soon hopefully.

John

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In reply to a message from John Schmincke sent Wed 30 Jan 2008:

John,
I’ve noticed a similar situation when one bank at idle is carrying
a slightly greater load. By this I mean the bank that’s puffing is
slightly being overrun by the more energetic bank. I have noticed
this on several of my cars while adjusting the butterflys at idle.
The manual states you should have a 0.002 gap at the bottom of the
butterfly. However, the balance of the butterflys is just a
starting place. ANY additional air getting into one side will make
it the energetic bank. To check this out manually move the non
missing throttle slightly open and see if it clears up. If it
remains unaffected, you have at least eliminated one more
possibility.

(BTW on left hand drive cars, the A bank is in front of the classy
high maintenace passenger).

For a controversial tid bit, the balancing of the burtterflys is
strictly for idle and coming off idle operation. From there on the
differences are buried. IE: wide open= what is butterfly balance at
idle??

Noel–
The original message included these comments:

I have a 92 XJS coupe with a V12/auto. From day one, I have noticed a
puffing from the exhaust tip on the passenger side…never can remember
which is A and which is B. I have also been chasing a FF44 code for 3 1/2


'92 XJS Conv, '88 XJS, 68 XKE, 1914 &'15 Ford Model T’s
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

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That big cross-over pipe at the back of the engine balances out any
difference in the throttle opening at or near idle. The AAV feeds the
left bank only. Does it create an imbalance?

My $0.02

Dave Harvey
89 XJ-S V12 Marelli [still waiting to install the exhaust system]
Los Angeles, Ca.

Jags+30jugs wrote:

The manual states you should have a 0.002 gap at the bottom of the
butterfly. However, the balance of the butterflys is just a
starting place. ANY additional air getting into one side will make
it the energetic bank.

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In reply to a message from Dave Harvey sent Thu 31 Jan 2008:

I agree, for the most part the spec for the throttle plate setting
is to prevent the plates from getting stuck in the bores due to
thermal expansion…however they do need to be reletively close in
order for all the other adjustments to mean anything.

Dave
Atlanta–
The original message included these comments:

That big cross-over pipe at the back of the engine balances out any
difference in the throttle opening at or near idle. The AAV feeds the
left bank only. Does it create an imbalance?


Penfold99
Atlanta, GA, United States
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John,

What kind of plugs did you use?  NGK?

What did you set the gap to?  0.025 inches?

The Marelli cars have a jumper plug for different octane fuels

located on the right rear of the engine bay (see the owner’s manual).
Is the plug in or out? If the plug is still in, take it out. If
it’s out, plug it in. Write back and let me know if this makes any
difference.

BTW, did you have high NOX numbers on your last smog test?  I'm

thinking about a lean misfire.

Did you do an archives search for F44?   Seems to me that comes

up often and there were some fixes mentioned. None of my cars have
codes, so I’m not up on them at all.

Regards,

Paul M. Novak

1990 XJ-S Classic Collection convertible
1984 XJ6 Vanden Plas
1969 E-Type Fixed Head Coupe
1957 MK VIII Saloon
1985 XJ6 Vanden Plas (parts)
Ramona, CA
@Paul_M_Novak1-----Original Message-----
From: owner-xj-s@jag-lovers.org [mailto:owner-xj-s@jag-lovers.org] On
Behalf Of John Schmincke
Sent: Wednesday, January 30, 2008 3:33 PM
To: xj-s@jag-lovers.org
Subject: Re: [xj-s] Fw: I’m Stumped!!!

Hi Mike and thanks for your thoughts. The injectors are good as they
were
just tested when serviced. I looked all over Tucson today for a noid
light.
Found one for Bosch but can’t pick it up until Thursday. I am curious to
give it a try though. My injection harness looks pretty good for a 92
but a
wire could have been pinched somewhere over the years.

Spark: I’ll give this a try also if the noid light test doesn’t yield
anything. The 2 coils were replaced also within the last 7 months with
new
original equipment. That also made a slight difference in making the
engine
run smoother. My original coils were working fine as far as I know but
had
that aged look. I still have them anyway.

Plugs are new. I am hoping they are okay but will change them out if
needed.
Plug wires are seated properly both on the plugs and in the cap.

Good luck! You bet! I’ll post a fix when I find it and hope it helps
someone
else down the road.

I suspect the FF44 is hinging on this.

John

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Penfold99 wrote:

I agree, for the most part the spec for the throttle plate setting is
to prevent the plates from getting stuck in the bores due to thermal
expansion…however they do need to be reletively close in order for
all the other adjustments to mean anything.

OK, we’ve got one report that the puff-puff exhaust that seems so
common with our cars is due to one bank trying to pull harder than
the other, and another suggestion that the butterflies need to be set
relatively close to avoid such an imbalance between banks. I think
the thinking among the engineers involved – Bywater can confirm –
is that the balance pipe is big enough to ensure that both banks see
the same throttle at idle no matter what, even though there’s an AAV
on one side and a SAV on the other.

If imbalanced throttle really is the problem, wouldn’t we expect it
to be more throttle on the B bank where the AAV is? The SAV only
flows during cold start or when the A/C compressor is engaged, but
the AAV flows all the time.

If it turns out that the problem is that the B bank is getting a bit
more throttle than the A bank, perhaps what we should do is alter the
throttle linkage adjustment procedure slightly. The thing to do
would be to use different feeler gauges on the two sides, a slightly
thicker one on the A bank side. Since setting the butterfly closing
is the first step of the linkage adjustment, all the succeeding
adjustments can be made as per the ROM instructions and it should all
work out fine.

Anybody wanna try this? To be a valid test, I would think somebody
would have to go through the entire linkage adjustment procedure
twice; first by the book with the .002 gauge used both sides and
driven around a couple of days to verify how it behaves, and then
again with perhaps a .0015 gauge on the B side and a .0025 gauge on
the A side and see if a difference is noted.

– Kirbert

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Jags+30jugs wrote:

For a controversial tid bit, the balancing of the burtterflys is
strictly for idle and coming off idle operation. From there on the
differences are buried. IE: wide open= what is butterfly balance at
idle??

You wouldn’t believe how much trouble I went to trying to explain
this rather simple concept to a bunch of managers at Pratt & Whitney
Aircraft. Without success, I might add.

The items in question were the afterburner spray rings for the F-100
engine in the F-15 and F-16. The spray rings are concentric tubes
with holes that spray great heaping gobs of fuel into the tail end of
a jet engine when you want to go reeeeally fast and don’t care how
much fuel you burn in the process.

For this engine, P&WA had developed an entirely new idea in spray
rings. Rather than being round tubes, they were oval. They had
holes around the ID, and there were “pintles” that were attached to
the OD surface, ran through the center of the tube (the short way
across the oval), and jammed into these holes to plug them. When
fuel pressure was applied, it would distort the tube, making it less
oval and more round, which would pull the pintles out of the holes
and allow the fuel to pass through and spray. Really, a stroke of
genius.

The implementation was awful, unfortunately. The pintles were
supposed to remain closed up to 30 psi, and then the flow varied with
pressure up to about 250 psi. They calibrated the flow at 100 psi,
being logically about midspan in the flow range. This makes about as
much sense as synchronizing your butterflies at 1/3 throttle rather
than at idle.

The critical operating point for a fighter jet is “upper left hand
corner” – meaning, as you view the operating realm on a chart of
speed vs. altitude, very high and very slow. It’s where having an
afterburner that doesn’t flame out on you means life or death in a
dogfight. High and slow means the air is very thin, so even at full
afterburner these spray rings were operating at just barely cracked
open.

These rings were ugly things. Simple idea, but once you attached
mounting bosses and plumbing connections things get messy. Each of
these bosses stiffened the oval cross-section in that location, so it
wouldn’t de-ovalize as much adjacent to a boss when pressure was
applied. To compensate, they made the holes close to the bosses a
bit larger. And then they calibrated each pintle – using a method
that screwed up the ovalization of the tube, only allowing the local
area to change shape rather than the whole tube – to provide the
same flow at 100 psi. When operated at 30.5 psi, which is where they
operated at upper left hand corner, half of the pintles were still
stuck shut, and the flow from the others was all over the map. You
could even have one entire side of the engine getting all the fuel
while the other side got none at all. The fuelling spray pattern was
a mess, so the performance was poor and unpredictable. Some engines
would work better than others just by luck.

I tried and tried and tried to explain to these nimnuls that they
should be calibrating these spray rings at crack-open pressure. Who
cares if one pintle flows a little more than another at sea level
take off (where air is really thick, those spray rings are operating
near max pressure), you’ll never see the difference and there’s zero
chance of a flameout even if there was a difference. But getting a
uniform spray pattern at upper left hand corner would be worth its
weight in gold. And no changes to the hardware at all, just a
calibration procedure change.

If you wanna know how that worked out, just read any Dilbert cartoon
where Dilbert tries to explain something to his pointy-haired boss.

Later on, these dipwads came up with their own solution to the spray
ring issues: They redesigned the oval spray rings to operate at
higher pressures, popping open at 100 psi and operating all the way
to 600 psi. Goody, goody, the calibration procedure at 100 psi will
work great! No such luck, they changed the calibration pressure to
250 psi so it’d be mid-range again. And, to their amazement, they
never seemed to work significantly better at upper left hand corner.

Sometime later, they did away with the oval spray rings altogether,
since experience had proven that they didn’t perform well at upper
left hand corner. And with that, yet another good idea got flushed
down the crapper and will probably never be heard from again.

– Kirbert

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1 Like

In reply to a message from Kirbert sent Thu 31 Jan 2008:

Let’s return to John’s problem…
The butterfly debate is easily dismissed if his misfire/puffy
exhaust issue happens at throttle open settings…or is it only at
idle. Can you stick something in the throttle turnsdial that is sa
1/4 to 1/2’’ thick to get the throttles off idle, and the engine
turning about 1500-2500 RPM, and listen carefully and feel the
exhaust pipes again to see if any inconsistancy between banks shows
up.

Dave
Atlanta–
Penfold99
Atlanta, GA, United States
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In reply to a message from Kirbert sent Thu 31 Jan 2008:

Kirbert,
I envy your experience at PWA.
The oval sounds good in concept. Hard to implement. seems it would
also be susceptible to fatigue in thee long run.
I’ve had debates over this simple bit of high importance
maintenance with many foreign car owners. Oh, Well!

Noel

This problem, I assume, is only at idle and off idle. OTW how would
you know. The V12 is a bugger determining if it is not running
smooth on the go.

However FF44 does seem to say you could have a broad range of RPM
coupled with missing, providing the FF44 isn’t set during idle and
remains on during wider throttle operation.
If this problem is across the RPM range, my suggestion about
butterflys is self cancelling.–
The original message included these comments:

For a controversial tid bit, the balancing of the burtterflys is
strictly for idle and coming off idle operation. From there on the
this rather simple concept to a bunch of managers at Pratt & Whitney


'92 XJS Conv, '88 XJS, 68 XKE, 1914 &'15 Ford Model T’s
Edmond, OK, United States
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In reply to a message from Jags+30jugs sent Thu 31 Jan 2008:

John:

I have discovered leaking HT wiring by running the car in a darl
place and watch for a light show.

The strove on individual cylinders is also a very useful indicator.

If you can find a way to attach vacum guage to the intake of each
bank, you can sense bank balance.

Or, a good ear, (not mine anymore) at teach tail pipe can discern a
weak cylinder. but, a piece of paper attached to a stick may indace
an off poattern one one pipe over the other. If you have a balance
tube on the exhaust, thses are not effective to isolate bankksm,
but only indicate overall condition.

If you have a way to measure the temperature at each exhaust port,
you may get a difference. Some racers use a hole in each primary
pipe to observe color of the exhaust. Dynometers sometimes use a
sensor in each primry to read temperature.

A lot easier on the T’s, just kill each vebrator till you find the
one that makeds the least difference in the running!!

Carl–
The original message included these comments:

I have a 92 XJS coupe with a V12/auto. From day one, I have noticed a
puffing from the exhaust tip on the passenger side…never can remember
which is A and which is B. I have also been chasing a FF44 code for 3 1/2


Carl Hutchins
Walnut Creek, California, United States
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In reply to a message from John Schmincke sent Wed 30 Jan 2008:

John,
Please tell us: is this an idle problem or give us your ideas on
the RPM!
Noel

_______-----QUESTION GUYS,
Is the FF error code system disabled at idle?–
The original message included these comments:

puffing from the exhaust tip on the passenger side…never can remember


'92 XJS Conv, '88 XJS, 68 XKE, 1914 &'15 Ford Model T’s
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

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Hello, Does someone knows about Spray rings. Are they welded tubes or seamless?