[v12-engine] 6.0 idle adjustments

I have a '95 xj12 6.0 and it has been idling rough lately. Whan the
car is hot and the AC is on, it vibrates a lot and shakes the car.

Well, I noticed that the idle stops on the throttle bodies looked
out of adjustment, so I found some instructions on the AJ6
engineering web site for adjusting the throttle linkage. I think I
got the idle stops adjusted right now and the car performs much
differently.

The good news is the idle is smooth now - very little vibration or
shaking. The bad news, though, is that the idle speed is faster
than I would expect. The tach reads about 900 - 920 when the engine
is hot, it’s in drive, and the AC is on full. It probably idles
about 1200 in neutral with the AC on, and maybe 1400 in neutral
with the AC off.

That’s a bit fast, isn’t it? If so, any suggestions how to bring it
down?

BTW, I tried to measure the voltage on the throttle potentiometer
as described on the AJ6 web site, but was not able to get a
reading. I see a green/yellow wire near the potentiometers, but
can’t seem to get a reading from the connector - should I pierce
the insulation to get a reading? I’m assuming the ignition switch
should be set one position shy of engaging the starter motor when
taking this measurement. The reading would be from that wire to
chassis ground, right?

Thanks for any suggestions you have for a newbie at this sort of
thing.

Rick Wilder–
Rick Wilder
Falls Church, VA, United States
–Posted using Jag-lovers JagFORUM [forums.jag-lovers.org]–

Visit the Jag Lovers homepage at http://www.jag-lovers.org for exciting services and resources including Photo Albums, Event Diary / Calendar, On Line Books and more !

In reply to a message from Rick Wilder sent Sun 14 Aug 2005:

… oh, another question I have that could be related. I discovered
a 6-conductor connector hanging loose at the rear-middle of the
engine cover, near the throttle potentiometer and don’t see where
this would plug in.

Anyone know what this would be - a test connector, maybe?

Rick–
Rick Wilder
Falls Church, VA, United States
–Posted using Jag-lovers JagFORUM [forums.jag-lovers.org]–
–Support Jag-lovers - Donate at http://www.jag-lovers.org/donate04.php

Visit the Jag Lovers homepage at http://www.jag-lovers.org for exciting services and resources including Photo Albums, Event Diary / Calendar, On Line Books and more !

Rick,

The good news is the idle is smooth now - very little vibration or
shaking. The bad news, though, is that the idle speed is faster
than I would expect. The tach reads about 900 - 920 when the engine
is hot, it’s in drive, and the AC is on full. It probably idles
about 1200 in neutral with the AC on, and maybe 1400 in neutral
with the AC off.

That’s a bit fast, isn’t it? If so, any suggestions how to bring it
down?

Have you tried to bring it down with the idle adjustment screw on the
AAV valve? I’m assuming the 6.0 shares this means of setting the idle
with the 5.3.

If you can’t get it any lower that way, start checking for vacuum
leaks.

BTW, I tried to measure the voltage on the throttle potentiometer
as described on the AJ6 web site, but was not able to get a
reading. I see a green/yellow wire near the potentiometers, but
can’t seem to get a reading from the connector - should I pierce
the insulation to get a reading? I’m assuming the ignition switch
should be set one position shy of engaging the starter motor when
taking this measurement. The reading would be from that wire to
chassis ground, right?

Some people separate the multipin connector enough to get a small
alligator clip in the gap. The test procedure was spelled out in
a posting by Jim Johnson on June 21 to the XJ-S mail list. If you can’t
find it in the archives I might be able to send it to you.

Ed Sowell
76 XJ-S
http://www.efsowell.us/ed/myJag.html

Visit the Jag Lovers homepage at http://www.jag-lovers.org for exciting services and resources including Photo Albums, Event Diary / Calendar, On Line Books and more !

In reply to a message from Rick Wilder sent Sun 14 Aug 2005:

1st thing did you set the throttle valves per Jag specs??? If no
then you need to do that. Then you go from there.–
Dr. Chadbourn Bolles
–Posted using Jag-lovers JagFORUM [forums.jag-lovers.org]–
–Support Jag-lovers - Donate at http://www.jag-lovers.org/donate04.php

Visit the Jag Lovers homepage at http://www.jag-lovers.org for exciting services and resources including Photo Albums, Event Diary / Calendar, On Line Books and more !

In reply to a message from Dr. Chadbourn Bolles sent Sun 14 Aug 2005:

I did set the gaps on the butterfly valves to .002 at idle, if
that’s what you mean. That did seem to eliminate the roughness that
had been there at idle. But the idle is now quite fast.

Thanks to Ed, I tracked down the description in the ‘‘XJS help’’ book
of the idle speed control on the AAV. Unfortunately I have not been
able to locate this on my car. Either it’s my inexperience or there
may be a different arrangement for this version of the motor.

If anyone has adjusted the idle speed on a '95 or '96 xj12, please
clarify.

Thanks,

Rick–
Rick Wilder
Falls Church, VA, United States
–Posted using Jag-lovers JagFORUM [forums.jag-lovers.org]–
–Support Jag-lovers - Donate at http://www.jag-lovers.org/donate04.php

Visit the Jag Lovers homepage at http://www.jag-lovers.org for exciting services and resources including Photo Albums, Event Diary / Calendar, On Line Books and more !

Rick,

On the odd chance it’s the same, open the bonnet and stand on the left
side of the engine compartment, close to the driver’s door. Bend over
the wing and peer done just aft of the air filter housing. See if there
is an aluminum tower about 4" high with large diameter hoses attached.
If so, that’s the infamous auxiliary air valve (AAV). On the side nearest
to you there is a hex head bolt. If it’s there, it’s the idle
adjustment.

Ed Sowell
76 XJ-S
http://www.efsowell.us/ed/myJag.html

Thanks to Ed, I tracked down the description in the ‘‘XJS help’’ book
of the idle speed control on the AAV. Unfortunately I have not been
able to locate this on my car. Either it’s my inexperience or there
may be a different arrangement for this version of the motor.

If anyone has adjusted the idle speed on a '95 or '96 xj12, please
clarify.

Visit the Jag Lovers homepage at http://www.jag-lovers.org for exciting services and resources including Photo Albums, Event Diary / Calendar, On Line Books and more !

In reply to a message from Ed Sowell sent Sun 14 Aug 2005:

I’m not seeing anything like that. Maybe I can dig up a
maintenance/repair manual on CD-ROM for my model/year and see what
they have for an idle speed adjustment procedure.–
Rick Wilder
Falls Church, VA, United States
–Posted using Jag-lovers JagFORUM [forums.jag-lovers.org]–
–Support Jag-lovers - Donate at http://www.jag-lovers.org/donate04.php

Visit the Jag Lovers homepage at http://www.jag-lovers.org for exciting services and resources including Photo Albums, Event Diary / Calendar, On Line Books and more !

In reply to a message from Ed Sowell sent Sun 14 Aug 2005:

i had same problem on my 1993 sixlitre.the aav is located
behind the right hand exhaust manifold,near the bulkhead in
the engine compartment it has a small adjusting screw,this
adjusts idle speed.you can get a cd rom from jdhc on this
model.hope this helps.–
cringer
–Posted using Jag-lovers JagFORUM [forums.jag-lovers.org]–
–Support Jag-lovers - Donate at http://www.jag-lovers.org/donate04.php

Visit the Jag Lovers homepage at http://www.jag-lovers.org for exciting services and resources including Photo Albums, Event Diary / Calendar, On Line Books and more !

Thanks to Ed, I tracked down the description in the ‘‘XJS help’’ book
of the idle speed control on the AAV. Unfortunately I have not been
able to locate this on my car. Either it’s my inexperience or there
may be a different arrangement for this version of the motor.

correct; the 6 litre in X300 didn’t have the AAV anymore (XJ40 did
tho). Are you quite sure there’s no vacuum leak somewhere?–
Arnoud

iMac, therefore I am

Visit the Jag Lovers homepage at http://www.jag-lovers.org for exciting services and resources including Photo Albums, Event Diary / Calendar, On Line Books and more !

In reply to a message from Rick Wilder sent Sun 14 Aug 2005:

I couldn’t say I’m entirely sure there is no vacuum leak, but I
haven’t found one. My mechanic took a quick look. He sprayed some
stuff around the air intake system and detected no change in the
idle, so he concluded there is not a vaccum leak.

The JTIS ROM is not available to me right now, so no help there. I
re-checked my settings of the butterfly valves and re-cleaned the
throttles. When set to a .002’’ gap I definitely get a very fast
idle. I can reduce the idle by changing the idle stops to close the
throttles. That brings up another symptom - when the car is hot, in
drive, and AC on, the engine makes a clattering noise. My mechanic
says he thinks this is pre-ignition. If I turn off the AC or shift
to N, this goes away. Hmmmm.

I guess it could be a vacuum leak I have not found yet, or maybe a
bad sensor. The engine is covered in electronic sensors, and I
don’t know what most of them are for :slight_smile: I suppose if one is giving
the Nippondenso Engine Control Module bad data, it could mess up
the idle. It seems to run fine otherwise, tho.

I hooked up my code reader and got the following:

P0112 IAT sensor 1 low input (first time I’ve seen this one)
P0507 Idle control system rpm high (duh!)
P0441 EVAP dmissions ccontrol purge flow fault (this one I’ve
gotten occassionally since I’ve had the car, so I don’t think it is
relevant)

Is IAT Input air temperature?

Well, I’m at a loss at this point.

Rick–
Rick Wilder
Falls Church, VA, United States
–Posted using Jag-lovers JagFORUM [forums.jag-lovers.org]–
–Support Jag-lovers - Donate at http://www.jag-lovers.org/donate04.php

Visit the Jag Lovers homepage at http://www.jag-lovers.org for exciting services and resources including Photo Albums, Event Diary / Calendar, On Line Books and more !

Is it possible you are using a different “left/right” definition?
Conventionally, the reference point it sitting in the drivers seat,
so for example cars for the US market have steering on the left side.

Using that convention the 5.3L engines have the AAV on the left.
Did this really change sides on the 6.0L

Ed Sowell
76 XJ-S
http://www.efsowell.us/ed/myJag.html

i had same problem on my 1993 sixlitre.the aav is located
behind the right hand exhaust manifold,near the bulkhead in
the engine compartment it has a small adjusting screw,this
adjusts idle speed.you can get a cd rom from jdhc on this
model.hope this helps.

cringer

Visit the Jag Lovers homepage at http://www.jag-lovers.org for exciting services and resources including Photo Albums, Event Diary / Calendar, On Line Books and more !

Aha! that makes more sense than moving it to the other side of the engine.
Ed Sowell
76 XJ-S
http://www.efsowell.us/ed/myJag.html

correct; the 6 litre in X300 didn’t have the AAV anymore (XJ40 did
tho). Are you quite sure there’s no vacuum leak somewhere?


Arnoud

Visit the Jag Lovers homepage at http://www.jag-lovers.org for exciting services and resources including Photo Albums, Event Diary / Calendar, On Line Books and more !

In reply to a message from Ed Sowell sent Sun 14 Aug 2005:

I have 95 6.0 with a rough idle problem. I changed the spark plugs
and cleaned the fuel injectors with no change. I finally found a
fix today! on each side of the engine, just behind the thermostats
are ‘‘idle control valves’’. These valves take air from the air
intake tube just before the throttle body and deliver it in to the
intake manifold essentially bypassing the throttle body.
Some times these valves get dirty and sticky and therefore need
cleaning. I removed the rubber inlet pipe to the valve and sprayed
WD40 into the valve and let it soak overnight. Started the car this
morning and to my delight the idle is just right. Happy Motering,
Danny–
The original message included these comments:

tho). Are you quite sure there’s no vacuum leak somewhere?


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

Visit the Jag Lovers homepage at http://www.jag-lovers.org for exciting services and resources including Photo Albums, Event Diary / Calendar, On Line Books and more !