[v12-engine] Yet again, idle and emissions problems with a 6.0LV12

V12-Engine
21

In reply to a message from Mark Eaton sent Thu 28 Jul 2016:

Hi Mark:
The HC and CO were BOTH ABOVE the norm. ONLY at idle.
2500 rpm test was good.
That was July 12.

Fast forward 2 weeks. The car was running beautifully and I
took her on a long 800+ miles trip.
Those were the results upon my return:

http://www.jag-lovers.org/v.htm?id=1469410491

My posts from Tuesday July 26 (after over 50 fresh gallons
of fuel) contained the following possible explanations:

  1. The test equipment was contaminated two weeks ago, now
    was in proper order (unlikely, but…)
  2. I drove the car 850 miles between then and now. Must have
    cleaned some gunk. Very likely old/bad fuel contributed
    too.
  3. There was an ignition system fault somewhere – plugs,
    rotor, wires, cap. (the misfire must have been gross and I
    would have noticed btw). The fault was corrected when I
    pulled/replaced the plugs and reseated the wires.
  4. Clearing the memory from the ECU did the trick. Perhaps
    there is a bad capacitor as suggested earlier, perhaps the
    idle trim does things to the mixture nobody can understand.
    In my view, this is the most likely reason for the pass
    today.

Steve–
The original message included these comments:

Personally, I think you have a lean misfire under closed loop (learnt
correction), not a too rich mixture.
The high HC thing with normal CO suggests a lean misfire. And if the default
settings are richer (as Kirby suggested) then your idle will smooth out
after battery disconnect.
Didn’t you put fresh fuel in? Did that coincide with your passing the
emissions test?

–
'95 XJS convertible - V12 6.0L
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22

In reply to a message from sbobev sent Thu 28 Jul 2016:

Steve,

You don’t have to be a professional engine tuner to use a
wideband sensor but you do need a basic understanding of
how air, fuel and spark come together, which obviously you
do.

With both your emissions and idle problem you’re working
in the dark a little because you don’t know for sure if
it’s rich or lean, but tools like a wideband sensor will
let you know which can help in solving the problem. Also,
if your mixture is off a little just because of a
accumulation of tuning errors caused by simple part
tolerances (nothing really wrong or broken) you can tweak
the wideband to get everything where it should be.

As far as your engines internals, probably just fine, but
a good compression test will tell you a lot.

Mike W–
The original message included these comments:

I don’t see how an amateur like me tweaking the ECU with a
wide-band O2 setup will accomplish anything.
I am beginning to doubt the internals of my engine. Sadly,

–
mike waldron
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23

I am beginning to doubt the internals of my engine.

I doubt that.

R. Bywater told me offline
that a 6.0L V12 that is running properly should be able to meet emission
standards even without the emissions equipment. Won’t happen for me…
:-((

Yes, it can happen for you. I can’t offer specifics because I have no experience with your engine. However, I can tell you that I went through a few years of failed tests. Each time I found something wrong and fixed it. Finally, I reached the point where it always passes. Now all I do for the biannual test is change the plugs, check the coolant temperature sensor, and take it to the test station.

Ed Sowell
'76 XJ-S coupe, red
http://www.efsowell.us

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24

In reply to a message from Ed Sowell sent Fri 29 Jul 2016:

Thank you for the encouragement Ed.
I bet you didn’t just fail the idle test, you failed both
speeds.

Anyhow, this is the first time the car failed. And yes, I
have gone through EVERYTHING in the engine bay.
CTS, CPS, ATS, FPR, flywheel sensor, plugs, wires, rotor,
cap, injectors, vacuum line, throttle bodies, TPS, two sets
of O2-sensors, new custom exhaust with modern 3-way
converters, a new ECU – you name it, I have been there.
The last thing on my to-do list is to rebuild the injector
harness.

I am at the point where I have 100% confidence in the car
and will drive her anywhere. Just went to New Hampshire and
came back. Will go coast to coast.

Yet, what has always bothered me is the fact that you can
see videos of V12 cars being awaken for a first time in
years that will idle smoother after than my painstakingly
sorted one.

And as of yet, I have not found any solid explanation why
that happens. Peter Crispin referred me to his friend, a
long time Jag master mechanic, who summer it like that –
yes, they all do that (rolling idle).

Best regards,
Steve–
The original message included these comments:

Yes, it can happen for you. I can’t offer specifics because I have no experience with your engine. However, I can tell you that I went through a few years of failed tests. Each time I found something wrong and fixed it. Finally, I reached the point where it always passes. Now all I do for the biannual test is change the plugs, check the coolant temperature sensor, and take it to the test station.

–
'95 XJS convertible - V12 6.0L
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25

In reply to a message from sbobev sent Thu 28 Jul 2016:

Interestingly Roger Bywater told me that my 93 6.0ltr
would be unlikely to pass the annual UK MOT if the
catalysts were removed & replaced with pre-CAT era down
pipes. So when my CATS eventually fail I will still fit
the pre-CAT down pipes but have some new low loss CATS &
O2 sensor bosses welded into a pair of front pipes.

Rgds.

Andy.–
The original message included these comments:

  • and in this case understand why it didn’t. R. Bywater
    told me offline that a 6.0L V12 that is running properly
    should be able to meet emission standards even without the
    emissions equipment. Won’t happen for me… :-((

–
1st reg. 01/08/1993 6.0ltr 2+2 convertible SAJJNAFS3ER188666
Lancashire, United Kingdom
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26

In reply to a message from Andy B B sent Sat 30 Jul 2016:

Andy:
This could be because in the UK, they do visual inspections
on the converters, just like in California.
The engine could run very well and produce low emissions,
yet, you won’t be able to pass the test if equipment is
missing.

Or may be, the UK limits are much lower than ours (we need
to have less than 200 ppm HC)

Steve–
The original message included these comments:

Interestingly Roger Bywater told me that my 93 6.0ltr
would be unlikely to pass the annual UK MOT if the
catalysts were removed & replaced with pre-CAT era down
pipes. So when my CATS eventually fail I will still fit
the pre-CAT down pipes but have some new low loss CATS &
O2 sensor bosses welded into a pair of front pipes.

–
'95 XJS convertible - V12 6.0L
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27

In reply to a message from sbobev sent Sat 30 Jul 2016:

Steve,

The U.K. limit is also 200ppm for hydrocarbons. I think it
would take a very knowledgable MOT tester in the U.K. to
spot missing CATS on a 23 year old XJS. If my CATS failed
I briefly considered gutting them & putting them back in
place but Roger Bywater told me that without the CATS in
place & functioning the car would more than likely fail to
meet the emissions requirements (Lambda, Carbon Monoxide &
Hydrocarbons) of the MOT - because of the age of & wear &
tear on the car’s engine & other relevant components
according to Roger Bywater.

Andy.–
The original message included these comments:

This could be because in the UK, they do visual inspections
on the converters, just like in California.
The engine could run very well and produce low emissions,
yet, you won’t be able to pass the test if equipment is
missing.

–
1st reg. 01/08/1993 6.0ltr 2+2 convertible SAJJNAFS3ER188666
Lancashire, United Kingdom
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28

In reply to a message from Andy B B sent Sat 30 Jul 2016:

Hmmm, wear and tear…and of course we know that this was
true for another 6.0L V12 owner (John, aka CJ95) who had no
cats and could never pass smog test in his home state.

He did a complete top-end rebuild and claimed that the
engine was silky smooth after that. He sold the car and is
no longer active on JL, so, we don’t know if that work paid
off in the long run.

BTW, how many miles do you have on your car? I just clocked
97,000 miles

Steve–
The original message included these comments:

The U.K. limit is also 200ppm for hydrocarbons. I think it
would take a very knowledgable MOT tester in the U.K. to
spot missing CATS on a 23 year old XJS. If my CATS failed
I briefly considered gutting them & putting them back in
place but Roger Bywater told me that without the CATS in
place & functioning the car would more than likely fail to
meet the emissions requirements (Lambda, Carbon Monoxide &
Hydrocarbons) of the MOT - because of the age of & wear &
tear on the car’s engine & other relevant components
according to Roger Bywater.

–
'95 XJS convertible - V12 6.0L
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29

Interestingly Roger Bywater told me that my 93 6.0ltr
would be unlikely to pass the annual UK MOT if the
catalysts were removed & replaced with pre-CAT era down
pipes.

I dunno if it’s true everywhere, but I think in some areas emissions testing is based on the standards in force when the car was built. It would make sense that your car isn’t expected to pass standards that didn’t exist when it was built. When a 1980 was built, the EPA standards were rudimentary and I don’t know if there were any standards in the UK or not, so one could see how it might be relatively easy for a 1980 to pass a test. Things were MUCH stricter in the US by 1993, however, and performing an emissions test on a 1993 car might prove challenging indeed if the car isn’t completely up to snuff.

– Kirbert

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30

In reply to a message from sbobev sent Sat 30 Jul 2016:

Steve,

Just over 72,000 miles but the car is not used anywhere
near as much as it should be. The garage I use for the MOT
is 200 yards down the street from home & I usually try &
do 80 miles in the couple of days before the MOT & then
make sure I drive the car on quiet roads for 10 miles
right before the MOT emissions test & the car will then
pass the emissions test comfortably. If I don’t get chance
to use the car & take it to the garage cold, the tester
leaves the car on a fast idle for several minutes to get
it fully warm/hot or it does fail the emissions test.

Do you have spare fuel & ignition ECUs to substitute to
see if that makes any difference to the emissions?

Andy.–
The original message included these comments:

BTW, how many miles do you have on your car? I just clocked
97,000 miles

–
1st reg. 01/08/1993 6.0ltr 2+2 convertible SAJJNAFS3ER188666
Lancashire, United Kingdom
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31

In reply to a message from Andy B B sent Sat 30 Jul 2016:

Hi Andy:
Thanks for chiming in. When you say fails, do you mean it
fails idle? Or both idle and high speed?

As of my 1st failure at the emission station – I did drive
the car ca. 200 miles the week before the test, and on the
day of the test, it was fully warmed when I got to the
station.

I do have two ECUs. If it fails agin in two years, I will
swap the ECUs to see if it will make a difference.

For now, enjoying cruising with the top down and getting
lots of thumbs up from onlookers :-)))

Steve–
The original message included these comments:

Just over 72,000 miles but the car is not used anywhere
near as much as it should be. The garage I use for the MOT
is 200 yards down the street from home & I usually try &
do 80 miles in the couple of days before the MOT & then
make sure I drive the car on quiet roads for 10 miles
right before the MOT emissions test & the car will then
pass the emissions test comfortably. If I don’t get chance
to use the car & take it to the garage cold, the tester
leaves the car on a fast idle for several minutes to get
it fully warm/hot or it does fail the emissions test.
Do you have spare fuel & ignition ECUs to substitute to

–
'95 XJS convertible - V12 6.0L
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32

In reply to a message from sbobev sent Sat 30 Jul 2016:

Steve,

The car has never failed on the natural idle test but it
last failed the 1st fast idle test on carbon monoxide &
Lambda in 2013 but it passed on the 2nd fast idle test -
when it was ‘‘hotter’’

Andy.–
The original message included these comments:

Thanks for chiming in. When you say fails, do you mean it
fails idle? Or both idle and high speed?

–
1st reg. 01/08/1993 6.0ltr 2+2 convertible SAJJNAFS3ER188666
Lancashire, United Kingdom
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33

And my local Jaguar authorised agent also stated “they all do that” when I
commented about the erratic idle. That was an '83 5.3 HE.-----Original Message-----

And as of yet, I have not found any solid explanation why that happens.
Peter Crispin referred me to his friend, a long time Jag master mechanic,
who summer it like that – yes, they all do that (rolling idle).

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34

In reply to a message from Mark Eaton sent Sun 31 Jul 2016:

Yep…Same issue with my 89. Lucas Constant Energy ignition.–
The original message included these comments:

And my local Jaguar authorised agent also stated ‘‘they all do that’’ when I
commented about the erratic idle. That was an '83 5.3 HE.

–
Matt 73 OTS
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35

In reply to a message from Mark Eaton sent Sun 31 Jul 2016:

Mark
I wondered if the ‘‘rough’’ idle could be a result of the
compromise when the injectors were batch fired as they
are. Hard to imagine at low air speeds an absolutely even
mixture reaching each cylinder…
Matt–
The original message included these comments:

And my local Jaguar authorised agent also stated ‘‘they all do that’’ when I
commented about the erratic idle. That was an '83 5.3 HE.

–
Matt Furness 85XJS-HE 5 Speed Manual
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36

In reply to a message from MattFurness sent Tue 2 Aug 2016:

Gee, reading all this stuff going on here makes me realise
how lucky we are down here in New Zealand.
Our version of the smog test goes like this:

Any visible smoke blowing whilst driving? No, then your
good to go.

Cheers
Mark–
Mark Brown 71 S3 Etype
Ohope beach, New Zealand
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37

Hi Matt

Good point.

NO ONE batch fires injectors anymore. Not if you want to pass emissions and
don’t want fuel puddling on the walls and valves.
Also the drop spray pattern is impacted by the air velocity.

Fuelling is of course dependent on the rail pressure, which in turn is
managed by a crude pressure regulator … and we’ve established (on this
list) that the manifold pressure signal is “lumpy”.

Could it be a case of filtering the MAP pressure signal to the FPR to
“smooth” out the signal at low rpm? i.e. feed it via a plenum box.

Or we could ask the opposite question. Who has got a smooth idle? And if so,
how was that achieved?

Cheers
Mark-----Original Message-----

I wondered if the ‘‘rough’’ idle could be a result of the compromise when
the injectors were batch fired as they are. Hard to imagine at low air
speeds an absolutely even mixture reaching each cylinder…

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38

In reply to a message from Mark Eaton sent Tue 2 Aug 2016:

Mark
How sensitive are the pressure regulators to pressure
‘‘spikes’’‘’?? As physical devices they may well be pretty
‘‘sluggish’’ to spikes…and the spikes were not very high
amplitude if I remember Marek’s graphs of this
phenomenon???
But easy to test this with…maybe a porous substance
jammed in the line to dampen pressure fluctuations…the
plenum will help if it is a larger diameter with a small
exit diameter…the pressure wave expands into the larger
diameter and only a small portion of the expansion wave
exits the smaller diameter so the intensity of the
pressure wave is reduced…but you can get pressure
intensification if your chamber length is the wrong
fraction of the pressure spike frequency…so could
misbehave…better to use the porous stuff.
Be an interesting test…
Regards
Matt–
The original message included these comments:

managed by a crude pressure regulator … and we’ve established (on this
list) that the manifold pressure signal is ‘‘lumpy’’.

–
Matt Furness 85XJS-HE 5 Speed Manual
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39

NO ONE batch fires injectors anymore.

Yeah, but that has nothing to do with idle quality. It’s because modern cars are required to have all sorts of on-board diagnostics, and that includes the capability of figuring out which individual cylinder is doing what and responding accordingly.

The reason the Jaguar V12 has an idle “stumble” is because the EFI system is constantly trying to run it too lean. It’s constantly bouncing on and off stochiometric, and the cycling up and down of the mixture to hold it in that range results in an idle that’s not what a V12 should be.

– Kirbert

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40

Hi Steve,

Makes you wonder whether there isn’t some means of tricking the ECU into
cycling faster. Overclocking a Jag ECU anyone? Double the ECU crystal
frequency? - Nah - that will result in half the fuel.

Certainly appears to be a software limitation.

I guess anyone with a Megasquirt or other solution could comment if they
have stable idle.

Rgds
Mark-----Original Message-----

This ‘‘stumble’’ at idle is for sure O2-sensor related. The car idles in
closed loop.

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