[x300] rough idle and misfire issues

X300
1

I’m experiencing rough idle and misfire problems with my 97 VDP.
I’ve been reading the postings for similar issues and many talk
about checking MAF and O2 sensor readings but none that I’ve found
describe what the numbers should be. I have an autoenginuity scan
tool but I’m very much a novice with it at this point. I just took
some readings at various rpms under load (trany in drive while
holding brakes) any I’m hoping someone can help interpret the data:

Fuel Trim:

B1S1 = 0 (no change with rpm)
B2S1 = 99.06 (number displayed in red and no change with rpm)
B1S2 = 24.18 (changes as throttle position changes then settles
back to this)
B2S2 = -24.96 (changes as throttle position changes then settles
back to this)

MAF (lb/min), no load:

0.01 @ 700rpm
0.02 @ 1500rpm
0.03 @ 2300rpm
0.04 @ 3400rpm

A few more notes:

  • I managed to make the beginner mistake of swapping the secondary
    O2 sensor cables so I read a number of the postings regarding the
    ‘‘oxygen Sensor Orientation’’ procedure. From that info I concluded
    that since my scanner says I’m running in closed-loop mode, that
    procedure would not help this condition. Perhaps that is not a
    correct assumption?

  • One other observation is that if I unplug the temp sensor, the
    rough idle goes away and the engine runs well until I reach
    highway speeds of about 55mph or greater. Then it will misfire
    intermittantly and sometimes, heavily.–
    BGNR
    –Posted using Jag-lovers JagFORUM [forums.jag-lovers.org]–

2

In reply to a message from BGNR sent Thu 24 Jul 2008:

Suggest you start by replacing the coolant temperature
sensor.There is lots in the archives on this subject.Be
careful to get the correct part–
95 XJR, 69 E-Type ots ,97 Miata ,‘X’-type SUV
Sierra Madre Ca 91024, United States
–Posted using Jag-lovers JagFORUM [forums.jag-lovers.org]–
–Support Jag-lovers - Donate at http://www.jag-lovers.org/donate04.php –

3

In reply to a message from BGNR sent Thu 24 Jul 2008:

Berner:
What version of AutoEnginuity are you using? I assume your numbers
are for short term trim. What are the Long Term fuel trim numbers?
On the X300 (at least the '95, '96 US models), the S2 sensors are
used for fuel trim, checked by the S1 sensors. This is reverse
from every other brand of vehicle I have worked on.
My experience for autoenginuity on an X300 is that the long term
and short term fuel trim numbers are reported for the S1 sensors,
but are meaningless. Also, the long term fuel trim number for both
the B1 and B2 sensors are the same number and is derived from the
average of the two banks. That’s why I say I believe you are
reporting your SHORT TERM fuel trim numbers.
Now, as to your S2 numbers, this data indicates a condition of the
O2s sensing a more rich condition on Bank 2 ( and trying to correct
by lowering the fuel)and a more lean condition on Bank 1 (by
raising the fuel).
Notice, I did not say that Bank 2 was rich, only that it was sensed
rich etc. The long term trim number would give an idea if the
system was reacting to B1 being lean, Or B2 being rich. In other
words, the long term trim has either set the trim for both banks
either too rich or too lean, and the other bank is trying to
correct itself via the short term trim.
Now, the rest is conjecture and is only my guess.
Thge trim numbers represent what the controller is trying to do to
correct what it has sensed. It is definitely not running right,
but and I suspect you have a failed O2 sensor. In order to
determine which one, look for the O2 sensor input, not the trim
values. You will probably find one ( Bank 2) holding a high value
and the other (Bank 1) low. That’s because the long term trim has
made both banks rich and Bank 1 is incorrectly still sensing lean
due to a falied sensor.
As to the MAF, those numbers are consistent with what mine reports
and I have never determined reasonableness.
Good Luck.–
Ross - 89 XJS, 95 XJ6, 98 XJR, 02 XJ8
–Posted using Jag-lovers JagFORUM [forums.jag-lovers.org]–
–Support Jag-lovers - Donate at http://www.jag-lovers.org/donate04.php –

4

In reply to a message from sparkenzap sent Thu 24 Jul 2008:

Hi,

It could also be worth checking the spark plugs. I was
having problems with my check engine light coming on, and
after having the codes pulled it all pointed at the post cat
o2 sensor, but rather than replace it straight off, my
mechanic had a good look around the car, especially as the
sensor checked out ok with his other tests.

It wasn’t until he checked the plugs that he discovered that
they were in a poor state, cracked etc etc, and were the
ones the car left the factory with (at 97k miles) - even
though the 70k miles service was stamped by a main dealer,
which is the one where the plugs should have been changed.

Just something else to check as the plugs are much less
costly than the o2 sensors.

Regards
Mark–
2001MY 4.0 LWB - http://www.jag-lovers.org/v.htm?1170489048
Wiltshire, United Kingdom
–Posted using Jag-lovers JagFORUM [forums.jag-lovers.org]–
–Support Jag-lovers - Donate at http://www.jag-lovers.org/donate04.php –

5

In reply to a message from BGNR sent Thu 24 Jul 2008:

I suggest getting the sensors reoriented and run the scan again.
the readings you are getting are of no use if the sensors were
switched, plus the S1 readings are of no use, they are out of
range.–
Brian Caro 96XJ6 4.0 63E-TypeS1FHC 05 XJ8 4.2
Newport News, VA, United States
–Posted using Jag-lovers JagFORUM [forums.jag-lovers.org]–
–Support Jag-lovers - Donate at http://www.jag-lovers.org/donate04.php –

6

In reply to a message from Brian Caro sent Thu 24 Jul 2008:

While it might very well be that the sensors have been
switched and the much touted re-orientation is required,
nothing in the data presented indicates that.
The O2 sensor raw data needs to be examined versus the
reaction of the control loop. If the B1S2 and B1S1 O2
sensors are reading lean, and/ or the B2S2 and B2S1 sensor
are reading rich, then the system is reacting correctly. If
not, then the s1 and s2 sensors need to be compared to
determine if one is faulted.
AFAIK, the system will not go into close loop, while wound
up with the re-orientation problem.
Again, The S1 FUEL TRIM numbers are meaningless because
there is no fuel trim using their data. Other scanners
besides AutoEnginuity do not report FUEL TRIM data for them.–
The original message included these comments:

In reply to a message from BGNR sent Thu 24 Jul 2008:
I suggest getting the sensors reoriented and run the scan again.
the readings you are getting are of no use if the sensors were
switched, plus the S1 readings are of no use, they are out of
range.

–
Ross - 89 XJS, 95 XJ6, 98 XJR, 02 XJ8
–Posted using Jag-lovers JagFORUM [forums.jag-lovers.org]–
–Support Jag-lovers - Donate at http://www.jag-lovers.org/donate04.php –

7

In reply to a message from anthony davenport sent Thu 24 Jul 2008:

Thanks, Anthony!

The temp sensor was my first guess also but it seems to be
working fine when I check it’s response with the scantool.
I’m now thinking that unplugging it is just taking the ECU
out of closed-loop and causing the fuel control to use some
default values. I may end up coming back to the temp sensor
before I’m done, however.

Regards,

-Bill–
The original message included these comments:

Suggest you start by replacing the coolant temperature
sensor.There is lots in the archives on this subject.Be
careful to get the correct part

–
BGNR
–Posted using Jag-lovers JagFORUM [forums.jag-lovers.org]–
–Support Jag-lovers - Donate at http://www.jag-lovers.org/donate04.php –

8

In reply to a message from sparkenzap sent Thu 24 Jul 2008:

Hi Ross,

Thanks for your help with this!

I have PC Version 6.0 of autoenginuity. Given your info, I ran some
more tests just now. Here is what I’m seeing:

S2 OUTPUT VOLTAGE WITH IGNITION ON BUT ENGINE NOT RUNNING:

         B1S2 = 1.02V    B2S2 = 1.02V

AT IDLE (722 RPM), COOLANT TEMP = 165F:

B1S2 - Mostly at 0.975V but occasionally drops briefly to 0.010V
then climbs back up quickly to 0.975V. Idle is rough except
when output voltage drops to 0.010V. While at low voltage,
idle is smooth.

B2S2 - Pretty steady at 0.010V. Drops slightly when B1S2 output
voltage drops.

B1S2 short-term trim is fixed at 0.00

B2S2 short-term trim is mostly at -24.96 but goes to approx. -5.46
briefly when B1S2 voltage drops to 0.010V.

Long-term trim for both banks never varies from -10.14.

I also ran the engine under load to 1400 rpm for about one minute
and B1S2 output voltage stayed at approx. 0.975V and B2S2 at 0.010V
without switching. It seemed that they only did the brief voltage
change when at idle.

Again, any insight as to what this might indicate is greatly
appreciated!

Regards,

-Bill–
The original message included these comments:

What version of AutoEnginuity are you using? I assume your numbers
are for short term trim. What are the Long Term fuel trim numbers?
On the X300 (at least the '95, '96 US models), the S2 sensors are
used for fuel trim, checked by the S1 sensors. This is reverse

–
BGNR
–Posted using Jag-lovers JagFORUM [forums.jag-lovers.org]–
–Support Jag-lovers - Donate at http://www.jag-lovers.org/donate04.php –

9

In reply to a message from robbinm sent Thu 24 Jul 2008:

Hi Mark,

Thanks for taking the time to reply!

I’ve tried three sets of plugs. The original Champions were in very
good shape but I replaced them with platinums, which was a mistake.
I now have a new set of NGKs and I’m confident they are good.

At this point, it really seems like something is messing up how the
ECU is controlling fuel mixture when in closed-loop mode.

Regards,

-Bill–
The original message included these comments:

It could also be worth checking the spark plugs. I was
having problems with my check engine light coming on, and

–
BGNR
–Posted using Jag-lovers JagFORUM [forums.jag-lovers.org]–
–Support Jag-lovers - Donate at http://www.jag-lovers.org/donate04.php –

10

In reply to a message from BGNR sent Fri 25 Jul 2008:

Bill:
I will try- but I do admit your numbers are not what I expected.

B1S2 - Mostly at 0.975V but occasionally drops briefly to 0.010V
then climbs back up quickly to 0.975V. Idle is rough except
when output voltage drops to 0.010V. While at low voltage,
idle is smooth.

So, Bank 1, sensor 2 is reading rich, but is controlling somewhat
(it cycles).

B2S2 - Pretty steady at 0.010V. Drops slightly when B1S2 output
voltage drops.

Bank 2, Sensor 2 is reading Lean

B1S2 short-term trim is fixed at 0.00

This is suprising. I would try scanning only this value (check
it alone). Sometimes Autoenginuity will skip reading one variable
without warning and show zero. But if it is really zero, no short
term trim is being applied to this bank, even though it is reading
rich.

B2S2 short-term trim is mostly at -24.96 but goes to approx. -5.46
briefly when B1S2 voltage drops to 0.010V.

So B2 is reading very lean (above), the trim is calling for lean.

Long-term trim for both banks never varies from -10.14.

There is only one long term trim although it is displayed twice.
It is calling for lean.

One more test. Make sure that S1 for each bank is essentially
giving the same readings as S2. Typically they should sort of
track each other (S1 and S2) with S2 being slightly behind S1
(that’s why you have the graph in the scanners).

With one bank calling for no trim when it needs it, and the other
calling for the wrong trim, something is apparently not working
right and freezing the fuel adaptation trim. I have noticed this
on one of my ecu’s and cannot say why it happens. Now, I would
tend to agree with Brian’s hunch concerning re-orientation
(assuming the S1 and S2 sensors agree). I have found that some
independents have the Jaguar software and can do this, and the
dealers should be able to do it, although it takes coaxing with
some of them. The minimum one hour labor charge should do it.–
Ross - 89 XJS, 95 XJ6, 98 XJR, 02 XJ8
–Posted using Jag-lovers JagFORUM [forums.jag-lovers.org]–
–Support Jag-lovers - Donate at http://www.jag-lovers.org/donate04.php –

11

In reply to a message from sparkenzap sent Fri 25 Jul 2008:

Hi Ross,

I’m going to give the sensor reorientation a try as suggested by
you and Brian. I will let you know what happens. I’m on vacation
next week so I’ll probably do it then.

I’ll be sure to let people know the result.

Thanks again,

-Bill–
The original message included these comments:

I will try- but I do admit your numbers are not what I expected.

So, Bank 1, sensor 2 is reading rich, but is controlling somewhat
Bank 2, Sensor 2 is reading Lean

–
BGNR
–Posted using Jag-lovers JagFORUM [forums.jag-lovers.org]–
–Support Jag-lovers - Donate at http://www.jag-lovers.org/donate04.php –

12

In reply to a message from BGNR sent Mon 28 Jul 2008:

Had the O2 sensor orientation done this week at Lee Jaguar in
Natick, MA. They knew what I was asking for and the price was as
expected at $113. They even washed the car, which was a nice
surprise.

The Jag is running much better now so It’s clear this procedure was
needed. I believe this also disproves the belief that the fuel
control running in open-loop mode is a necessary simptom for this
problem.

I still have an issue with some misfiring starting at around 55mph
but I’m waiting to see if that clears up on its own. If not, I
expect I can diagnose and correct that on my own.

Thanks again to everyone who responded to my request for help!

Regards,

-Bill–
BGNR
–Posted using Jag-lovers JagFORUM [forums.jag-lovers.org]–
–Support Jag-lovers - Donate at http://www.jag-lovers.org/donate04.php –

13

In reply to a message from BGNR sent Fri 8 Aug 2008:

-Bill

I am glad to hear you were satisfied. I have never heard of an 02
orientation what is it and what is done to the 02 sensors?–
Mike O’Connor 89XJS V12 Coupe 1995 XJ6 VP 1997 XJR
Derby NY, United States
–Posted using Jag-lovers JagFORUM [forums.jag-lovers.org]–
–Support Jag-lovers - Donate at http://www.jag-lovers.org/donate04.php –

14

In reply to a message from Mike O’Connor sent Sat 9 Aug 2008:

Hi Mike,

Sorry I’ve taken so long to reply. I’ve been away on vacation.
Below is a description of the O2 sensor orientation that I clipped
from this website. Hopefully, this will answer your question.

Regards,

-Bill

The ‘‘oxygen sensor orientation’’ procedure appears to be a common
procedure
in the UK. However, the US dealers aren’t familiar with it. When I
did eventually
get to an older master mechanic (at a Tennessee Jag dealer) he
explained it to
me. I don’t have it completely straight but the essence of it is
correct:

When the engine is operating it continually looks at the o2 sensors
and adjusts
the fuel trim to optimize the performance. If the sensors fail
(switching the
connectors on mine caused it) the control will get false readings
and over
correct to the point it doesn’t know where it is at. At that point
it switches into a
limp type mode (open loop) and runs off of preset tables which are
less efficient.
It does not self correct and it does not trigger engine codes.

There is a procedure on the factory diagnostic tools (JDS and PDU)
and the
high-end aftermarket tool which when run scans the o2 sensors,
makes sure
they are responding correctly, and resets the proper parameters in
the engine
management computer. It is a simple task and takes less than 1/2
hour.–
The original message included these comments:

I am glad to hear you were satisfied. I have never heard of an 02
orientation what is it and what is done to the 02 sensors?

–
BGNR
–Posted using Jag-lovers JagFORUM [forums.jag-lovers.org]–
–Support Jag-lovers - Donate at http://www.jag-lovers.org/donate04.php –