[x300] 95 X300 XJR6 severe miss-fire

Dear All,
I was out in my XJR on Tuesday night when it started to develop a
miss-fire. This got worse and worse to the point that it only just
managed to get back to my driveway. A quick look showed signs of
arcing on ALL SIX coil units (New 5 years ago) and very heavy black
soot on all six spark plugs. My first idea was that extream
overfueling could have fouled the plugs causing all the coils to
break down to the rocker cover instead. I plan to test the fuel
pressure regulator (if the diaphragm splits I believe fuel can be
pumped into the inlet via the vacuum hose), clean up the coroded
coil wells, clean the plugs and try again and see if the OBD shows
any faulty sensor behaviour. Whilst the rocker cover is off I will
also check that the valve timing is ok.
My scan tool shows % injector duty cycle, does anyone know what it
should be at idle?
Does anyone know the thread/fitting on the fuel line conection to
the fuel rail?
Any ideas or suggestions apreciated.

Thanks,

John–
JohnXJR
Lancashire, United Kingdom
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In reply to a message from JohnXJR sent Thu 26 Jul 2012:

To Update. Fuel pressure regulator seems ok. Coil wells cleand up.
Problem persists.
Checked the connection to the ECU seemed ok and area dry although I
could not disconnect the plugs because of the security bracket
covering them, retained by ‘one way’ screws.
My scan tool ‘Elmscan 5 compact’ showed normal sensor functions.

But Fault code P1176. aparently this is a manufacture specific
code. Does anyone know what it means?

The long term fuel trims are both at 77.3 and the short term fuel
trims both fluctuated between around 13 and 20. this was in closed
loop as the engine had not fully warmed up. Running badly so did
not want to run it for long.

Regards,

John–
JohnXJR
Lancashire, United Kingdom
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In reply to a message from JohnXJR sent Fri 27 Jul 2012:

When you donate, there are extras on this Forum such as:-

P1171 - System Too Lean - Banks 1 and 2 (Lean Fuel Fault)
P1172 - System Too Rich - Banks 1 and 2 (Rich Fuel Fault)
P1174 - System Too Lean - Banks 1 and 2 (Suspect HO2S)
P1175 - System Too Rich - Banks 1 and 2 (Suspect HO2S)
P1176 - Long Term Fuel Trim Too Lean - Banks 1 and 2 (FMFR)
P1177 - Long Term Fuel Trim Too Rich - Banks 1 and 2 (FMFR)
P1178 - Long Term Fuel Trim Too Lean - Banks 1 and 2 (AMFR)
P1179 - Long Term Fuel Trim Too Rich - Banks 1 and 2 (AMFR)

This and other information is easily accessable.

However as always, glad to help.–
The original message included these comments:

But Fault code P1176. aparently this is a manufacture specific
code. Does anyone know what it means?


Neil 70 '97 3.2S http://www.jag-lovers.org/v.htm?1242166704
MALDON, United Kingdom
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In reply to a message from Neil Maldon sent Fri 27 Jul 2012:

John:
That is an interesting set of data. The fact that the fuel trims
are all indicating rich and the engine is apparently running rich
would seem to indicate that it is NOT running in closed loop. In
closed loop, the ecu would tend to reduce the fuel.
I think it would be worthwhile to consider the MAF, which might be
commanding too much fuel for the system to correct for OR you might
be experiencing a condition that has been reported before and, (I
believe) I have experienced where the ecu locks up the fuel trims,
will not go into closed loop, and requires reset with a dealer
level software. The reset is called ‘‘re-adaption’’ of the lambda
sensors.–
Ross - 89 XJS, 98 XJR, 99 XJR, 02 XJ8
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In reply to a message from sparkenzap sent Sat 28 Jul 2012:

Thanks Guys,
If the engine is running rich but the fault say trim too lean, does
that mean that the ecu is trying to lean out the mixture but has
hit the limit of its adjustment range?
I was also advised to change the fuel filter.Apparently if not
changed regularly you can get reduced fuel pressure which results
in the injectors squirting rather than spraying. This means that
the fuel doesnt burn properly, causing bad runnning and symptoms of
a rich mixture. I plan to get a gauge to test the fuel pressure,
but changing the filter today did seem to improve things noticably,
in that the missing was ocasional and mild rather than constant
with the engine rocking about, although havent driven it yet.
Perhaps remaining missfire is a consequence of fouling the plugs?
I deleted the code and it did not return after runing the engine
for about 20 minutes.
How would I test the airflow meter? the output seemed to change
sensibly with revs but I do not know what it should be reading. I
believe you can get sprays to clean the filaments.

Cheers,

John–
JohnXJR
Lancashire, United Kingdom
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In reply to a message from sparkenzap sent Sat 28 Jul 2012:

try to get your hands on a scan tool where you can watch the
actual sensor data in graphical form.
you’ll want to see it swing back and forth high and low
voltage at idle for the o2 sensors on that bank, if there isnt
relatively quick swinging or a constant voltage then you may
have a bad o2 sensor which is causing the lean trim to take
effect and possibly stall the car.

on my fathers car the o2 sensors were mirroring each and the
data stream didnt make any sense, ended up being a bad ecu.–

In reply to a message from sparkenzap sent Sat 28 Jul 2012:

Apologies, I meant to say open loop - the engine was cold.
After the replacing the fuel filter it is running much better not
driven it yet as planning to replace plugs and test fuel pressure,
but ran it for 30 mins to warm up properly. The lean trim code has
not returned and the oxygen sensors switch regularly. The long term
fuel trims are both still at 77.3. Is that normal?–
The original message included these comments:

would seem to indicate that it is NOT running in closed loop. In


JohnXJR
Lancashire, United Kingdom
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In reply to a message from JohnXJR sent Tue 31 Jul 2012:

long term fuel trims when working properly should hover around
1-2% maybe as high as 5% but unlikely.

you should clear all codes as well as the self learn and let
it readjust.–

In reply to a message from JohnXJR sent Tue 31 Jul 2012:

John:
Many of us have experienced the LTFT indication stuck at the
high value with no apparent performance problem. Several of
us concluded that it was therefore a wrong indication rather
than the trims being actually that high. However, after I
reset my ecu, then reset my spare ecu using the adaption
procedure with WDS, the LTFT indication returned to normal
readings hovering between -3 to + 4 or so. It seemed that
the fuel mileage also went up a good bit, but I cannot
guarantee the validity of that.

What I have just reported is factually correct, but I cannot
explain what actually went on in the car nor if other
factors contributed to the events as reported.–
Ross - 89 XJS, 98 XJR, 99 XJR, 02 XJ8
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In reply to a message from sparkenzap sent Wed 1 Aug 2012:

As it seemed much improved by the fuel filter replacement, I took
it for a drive to the shop to buy some new plugs and then to the
supermarket and then home. As I aproached my home it was running
well and I was just thinking that it didnt need the new plugs, then
the severe misfire apeared suddenly and stalled as I stoped to make
a right turn. It started and ran just enoungh to make the turn but
then stalled again and would not restart. Fortunatly I was able to
roll down the hill to my driveway and some other motorists (who I
was obstructing) helped my push it onto my driveway.

I will change the plugs tonight, but the sudden nature of the fault
now makes me suspect the crank sensor, although it does give a
reading and there are no fault codes. Could bad fuel cause
intermittent problems?–
JohnXJR
Lancashire, United Kingdom
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In reply to a message from JohnXJR sent Fri 3 Aug 2012:

More confusion, New plugs made no difference. So today I syphoned
out all the petrol. There was the odd droplet and a blob of water
in the containers so I discarded that and then put the rest back
in. Car started and ran fine again. OBDII showed every thing ok.
stopped and restarted - ran badly. tried again and noticed scan
tool had a pop up box saying ‘OBDII BUS is shorted to VBatt or
Ground’ The OBD socket has always had an unreliable diagnostic
connection but I have not seen this message before. My first
thoughts are to check the wires to the socket for any obvious
damage. Not sure where to go from there. A bad wiring issue would
acount for the intermitttent nature and severity of the problem.
Any suggestions?

Thanks,

John–
JohnXJR
Lancashire, United Kingdom
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In reply to a message from JohnXJR sent Sat 4 Aug 2012:

check the maf to intake manifold coupler for tears, mine tore
and it had all kinds of running issues till I glued it back
together.–

In reply to a message from OneBadKitty sent Sat 4 Aug 2012:

Gents,

Last weekend I drilled out the screws holding the security bracket
and cleaned the ECU connections with WD40 and a toothbrush. There
was some blue/green corrosion on the female connectors, visible
when removing the white plastic section but not too much. I also
checked the condittion of the fuses/relays in the boot and on the
inner wings/fenders along with the white multiplug previously
mentioned on this forum. All apeared fine but the WD40 should help
keep them that way.
Engine ran much the same as before with a slight but regular miss-
firing which ocasionaly became worse.

The scan tool showed all sensors outputs to be sensible and change
as expected with revs. The mesages ‘P1176 long term trim too lean
(FMFR)’ (what does FMFR mean?) and ‘OBDII buss is shorted to V batt
or ground’ did not return.
As I had a spare set of coils, I swapped them over- that made no
difference.

Still thinking there may be a contaminated fuel issue, I ran the
engine again tonight in the hope it might clear once the fuel rail
etc had flushed through, as the missfire seemed to be better than
it was. Once the engine was warmed up, I conected my scan tool to
see if any codes had come back.

There was a new code: P0102 MAF/MAP low input
and the sensor readout showed the MAF sensor stuck at 0.00g/sec or
whatever the units are.
This had previously given a reading which increased with revs,
could this have been on its way out for a while reading high or low
to give faulty fuel trims before suddenly failing?
I did unplug it to check the condittion of the conector and
squirted some WD40 on the socket but I think the battery was
disconnected at the time.
Can I test the MAF sensor easily?
Also in time with this fault, the oxygen sensors had stopped
switching, staying at 1.2 v and short term fue trim -25. They had
been switching regularly previously once the engine was warmed up.

I am now considering the posibilities:

1.Has or could a failing MAF cause all the problems via grossly
wrong mixture?

2.Is it a contaminated fuel issue and I have some how managed to
damage the MAF / conection / setup in my attempt to clean up the
connections?

I guess the jobs for this weekend are to test the MAF and flush the
fuel rail, with the priority being to get the MAF reading again.
Any suggestions how I may test the MAF would be welcome to save
finding/buying a second unit from a breaker.

Advice much apreciated,

Thanks

John–
JohnXJR
Lancashire, United Kingdom
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In reply to a message from JohnXJR sent Tue 14 Aug 2012:

John

My own experience with the ECU connectors - see
http://tinyurl.com/6gz4el8
was that the blue verdigris was not only causing corrosion
in the obvious places but also tended to bridge between
contacts. This could be a very thin film of conductive
verdigris down in the depths of the ECU connector.

Although I appreciate you have cleaned it - can you be 1000%
certain the connector is ‘‘as new’’ with absolutely no leakage
between pins. This also applies to the flying connector of
course. The leakage caused havoc with my engine management
until eventually the car wouldn’t drive at all!

Also - check ALL the pins are present - at least two of us
have had a pin fall off due to corrosion.

Not the news you want to hear, but it is mighty sensitive in
there!

Best wishes from Jim Butterworth
http://jimbutterworth.co.uk/
.
Just because you’re not paranoid doesn’t mean they’re not
out to get you–
The original message included these comments:

was some blue/green corrosion on the female connectors, visible
when removing the white plastic section but not too much. I also


1995 3.2 Sport - www.jag-lovers.org/v.htm?id=1320795768
Somerset, United Kingdom
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In reply to a message from JohnXJR sent Tue 14 Aug 2012:

John, I believe that some scanners display the o/p volts
from the MAF (pin 2 possibly) and I am told that this should
be about 1.4v at idle increasing to about 4 to 5v at Red
Line Rev’s, this can be checked by locking into 2nd. gear
and giving it a blast on the road. Not sure whether the
increments are linear or not.
Hope that helps.–
The original message included these comments:

Can I test the MAF sensor easily?


Neil 70 '97 3.2S http://www.jag-lovers.org/v.htm?1242166704
MALDON, United Kingdom
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In reply to a message from Neil Maldon sent Wed 15 Aug 2012:

To follow up, this site has info. that is representative and
may help:

http://tinyurl.com/blzjtof--
The original message included these comments:

and giving it a blast on the road. Not sure whether the
increments are linear or not.


Neil 70 '97 3.2S http://www.jag-lovers.org/v.htm?1242166704
MALDON, United Kingdom
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In reply to a message from Neil Maldon sent Wed 15 Aug 2012:

Thanks Guys,

Jim, looking at your site the corrosion was nowhere near as bad as
on your connector and the pins looked good, it was the female
socket on the wires that had some corrosion but I will have another
look.
Neil, I do not trust it enough to take it out at the moment. I
believe you can check the MAF by measuring the resistance between
the pins - I need to know the expected values. Also it could be a
wiring conection issue preventing a reading on the ECU.

John–
JohnXJR
Lancashire, United Kingdom
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In reply to a message from JohnXJR sent Wed 15 Aug 2012:

Jim, Do you know if the pinouts are the same for the XJR, I assume
so as same sensors ect though I know the MAF is different spec.

John–
JohnXJR
Lancashire, United Kingdom
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In reply to a message from JohnXJR sent Wed 15 Aug 2012:

John, you’ll get a representative value with the car
stationary. Trouble is that the circuit in the MAF is active
not just resistive!–
The original message included these comments:

Neil, I do not trust it enough to take it out at the moment. I


Neil 70 '97 3.2S http://www.jag-lovers.org/v.htm?1242166704
MALDON, United Kingdom
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In reply to a message from Neil Maldon sent Wed 15 Aug 2012:

Neil, I meant so that I could see if the filaments were burnt
out/damaged with the unit disconected, not with the engine running.
It may well be that it was reading ok and the signal has compleatly
gone because I disturbed the connectors at the ECU and various
fuses/relays. I guess that a mass flow stuck at oo and the error
code means no measurment so unless the filaments have totaly failed
I guess it points to wiring
John–
JohnXJR
Lancashire, United Kingdom
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