Well, after doing the throttle cable adjustment and throttle body
cleaning last week, my 96 XJ6 VDP was running GREAT. It had idled
down to well under 1000 RPM in both Drive and Park, and was no
longer continuing to ‘‘pull’’ after I let off the throttle. It drove
great all weekend until this morning. I noticed it
started ‘‘pulling’’ again on its own (the best way I can describe it
is if you just slightly left your foot on the gas pedal just enough
to make it accelerate just slightly). So I parked the car and
noticed it’s back to idling at around 1400 RPM in Park and 900-1000
RPM in Drive, just like it did after I adjusted the throttle cable
but before I cleaned the throttle body. I checked the throttle
cable, and it’s still adjusted correctly. There’s no way the
throttle body got that gunked up with carbon in less than a week’s
worth of driving, is there? If that’s the case, there’s something
else wrong that’s causing that, OR it may be a totally different
problem maybe? Any help on this would be appreciated. Anything else
I need to clean out? Thanks.–
1996 Jaguar XJ6 VDP, 1993 Lincoln Mark VIII, & 1972 Lincoln
Salisbury, NC, United States
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In reply to a message from Jagfan1986 sent Mon 24 Sep 2007:
After checking in the X300 E-book on this site, I’m beginning to
wonder if maybe my problem is the throttle body spring? Any
thoughts?–
1996 Jaguar XJ6 VDP, 1993 Lincoln Mark VIII, & 1972 Lincoln
Salisbury, NC, United States
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It could be, next time you stop the car, and the idle is high, open the hood
and close the throttle with your finger and see what happens. My V12 has two
springs per throttle body whereas the parts catalogue has only one listed.
The PO might have had the same problem.
Regards,
Jeff Watson.
Sydney, Oz.
1995 V12 X300.
In reply to a message from Jagfan1986 sent Mon 24 Sep 2007:
After checking in the X300 E-book on this site, I’m beginning to
wonder if maybe my problem is the throttle body spring? Any
thoughts?Subject: Re: [x300] Help! High idle is back 
In reply to a message from Jagfan1986 sent Mon 24 Sep 2007:
Your car exhibits all the symptoms of a failing Idle Air Control
Valve/ Stepper Motor. This part regulates the air bypass in the
throttle body to control the idle. Failure in it is common and it
is an easy repair, just look out for the small screws that hold it
in, they are 4mm (small) and put in with Loctite and can be bears
to get loose. Failure mode is either high or low, but smooth, idle.–
Brian Caro 96XJ6 4.0 63E-TypeS1FHC
Newport News, VA, United States
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I’d go with spring. It’s the lowest common denominator next to a vacuum
leak.
XJRGUY> From: Jagfan1986 brownrr48@aol.com
Reply-To: x300@jag-lovers.org
Date: Mon, 24 Sep 2007 01:38:42 +0200
To: x300@jag-lovers.org
Subject: Re: [x300] Help! High idle is backIn reply to a message from Jagfan1986 sent Mon 24 Sep 2007:
After checking in the X300 E-book on this site, I’m beginning to
wonder if maybe my problem is the throttle body spring? Any
thoughts?1996 Jaguar XJ6 VDP, 1993 Lincoln Mark VIII, & 1972 Lincoln
Salisbury, NC, United States
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In reply to a message from Tim sent Mon 24 Sep 2007:
A few years ago, Jaguar had a recall for the EGR, EPROM and
Throttle Spring repacement. After I changed the Spring (upgraded
part #) I sometimes noticed that the Throttle would still not
return to the STOP with the engine running, but was fine with
ENGINE OFF.(airflow holding the throttle open) I ended up unwinding
the spring 1/2 turn, cutting off he excess and rewinding the spring
one more turn tighter and never had another fault.(this is the
lower spring) I did this with every car afterward and I have talked
to other mechanics who found the same result. Sometimes you just
ignore the factory bulletins and go with what works. bob–
The original message included these comments:
I’d go with spring. It’s the lowest common denominator next to a vacuum
leak.After checking in the X300 E-book on this site, I’m beginning to
wonder if maybe my problem is the throttle body spring? Any
thoughts?
–
Owning and Repairing Jaguars Since the Early 70’s
Decatur, TX., United States
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In reply to a message from Jagfan1986 sent Mon 24 Sep 2007:
I had a similar problem with my 95 xj6. What I experienced
was a high idle and often push me down the road like yours.
I cleaned the throttle body twice; the second time better
than the first and still had the problem. After further
investigation I found that the throttle did not return, it
was sticking partially open. I took an unorthodox approach
and sprayed the throttle shaft (on the outside) with PB
spray (great stuff) twice. It returned to normal and to
date the problem has not returned. Will this work for you I
have no idea. But I would do it again.
Gus–
GusG
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In reply to a message from Jagfan1986 sent Mon 24 Sep 2007:
Hi JagFan,
It does sound like a weak throttle return spring. Don't worry
about gunk for another 20k to 30k miles. With it idling high, try
to manually return the throttle and see if it lowers. If so, I
would replace the spring. I would have suggested checking your
adjustment again, especially if you adjusted it while the engine
was cold, but I see you already did. If this doesn’t provide a
solution, try removing the idle air control valve, leaving it
wired, and have a helper turn on the ignition while you observe it
for movement. Do this with the enginge hot, and then with it
cold. It isn’t necessary to start the car, just watch to see if it
actuates once the ignition is turned on. If it doesnt, I would
suspect it. Good luck and let us know.
Matt
'95 VDP–
The original message included these comments:
but before I cleaned the throttle body. I checked the throttle
cable, and it’s still adjusted correctly. There’s no way the
throttle body got that gunked up with carbon in less than a week’s
worth of driving, is there? If that’s the case, there’s something
else wrong that’s causing that, OR it may be a totally different
problem maybe? Any help on this would be appreciated. Anything else
I need to clean out? Thanks.
–
Trilithon
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In reply to a message from Trilithon sent Mon 24 Sep 2007:
Well I don’t think it’s the throttle spring anymore. Actually, the
throttle body is CLOSED when the engine is running. Is this normal?
I can manually open the throttle body (obviously, making the engine
rev), but I can’t turn the throttle body in the other direction at
all. How is the car breathing to run with the throttle body closed
like that? This is starting to concern me. I removed the IACV and
it was coated in carbon (I didn’t clean it when I cleaned the TB),
so I wiped the carbon off of it and used a q-tip for the spaces I
couldn’t reach. After putting it back on the car and taking it for
a test drive, it made no improvement whatsoever. Apparently either
the IACV needs to be replaced, or it’s some other issue. Once I
have someone on hand to help me, I’m going to try to test the IACV
as suggested. Assuming it may be the IACV, I called the local Jag
dealer and was told $210 for a new unit. Anyone know of a source
where I could get it cheaper than that if it is, in fact, the
problem here?–
1996 Jaguar XJ6 VDP, 1993 Lincoln Mark VIII, & 1972 Lincoln
Salisbury, NC, United States
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In reply to a message from Jagfan1986 sent Mon 24 Sep 2007:
Before spending lots of money it pays to reset the
butterfly. I got this tip from Dave Marks. The heat changes
seem to move the butterfly on its spindle. Loosen the two
small (torx?) screws holding the butterfly to the spindle
just enough to allow it to reseat when you flip it open and
closed. Then retighten them and check it isn’t sticking when
you flip it open & closed. While it’s off make sure you
spray the stepper motor channel with carb cleaner from both
sides.
It’s cheap and has fixed idle problems for me in the past.
John–
The original message included these comments:
Well I don’t think it’s the throttle spring anymore. Actually, the
throttle body is CLOSED when the engine is running. Is this normal?
I can manually open the throttle body (obviously, making the engine
rev), but I can’t turn the throttle body in the other direction at
all. How is the car breathing to run with the throttle body closed
like that? This is starting to concern me. I removed the IACV and
it was coated in carbon (I didn’t clean it when I cleaned the TB),
so I wiped the carbon off of it and used a q-tip for the spaces I
couldn’t reach. After putting it back on the car and taking it for
a test drive, it made no improvement whatsoever. Apparently either
the IACV needs to be replaced, or it’s some other issue. Once I
–
twojagsv8
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In reply to a message from Jagfan1986 sent Mon 24 Sep 2007:
The butterfly should be completely closed at idle. Air for idle is
via the ISCV and related passageways. If when you removed the ISCV,
and it was full of crud, you can imagine what is in the tiny air
passages that it controls. If you removed the TB, and removed the
ISCV and the TPS, you can really get after cleaning the TB with
spray cleaner, pieces of wire, etc. to clean the passageways. You
can also ‘‘dunk’’ it in cleaner if you have some available.
In respect to the other poster, I would not start loosening the
screws that hold the butterfly flap it the shaft. They are not
adustable.
Of course it could be the ISCV, but before I spent $200, I would
try another complete cleaning.–
The original message included these comments:
Well I don’t think it’s the throttle spring anymore. Actually, the
throttle body is CLOSED when the engine is running. Is this normal?
I can manually open the throttle body (obviously, making the engine
–
uncle
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In reply to a message from uncle sent Tue 25 Sep 2007:
I had this issue and posted about it a few months ago &
concur with all the advice given so far.
One thing I did to reduce the carbon fouling you describe
was to install a breather cleaning system(Like ‘‘JAZ’’ but
larger. I am still unsure if is helping but the problem has
not returned. What I suspect helped most was to thoroughly
clean the breather gauze in the cam cover. This is an easy
job but you’ll need to swill it out several times and let it
dry off completely before you re-fit it.You can clean and
re-gap the plugs while waiting? I wonder if anyone has
drilled out the rivets that hold the cover over the gauze
and made a more service-friendly arrangement?
Before you try removing the ISCV ,I suggest you research
methods for removing the retaining screws w/o breaking
them.There is lots in the archives.–
95 XJR, 69 E-Type ots,89 RX-7 conv,97 Miata ,‘X’-type SUV
Sierra Madre Ca 91024, United States
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In reply to a message from uncle sent Tue 25 Sep 2007:
While it may appear that the butterfly is completely closed a small
gap is required and actually a critical adjustment. I seem to
recall (alldata?) from my idle wars, a static setting of .005’’ but
then final adjustment is required by scanning equipment able to
read IACV position. It is tempting to try to close this small gap
in cases of high idle but it is the amount of air allowed through
this small gap that references the IACV to the midpoint of it’s
range.–
The original message included these comments:
The butterfly should be completely closed at idle. Air for idle is
via the ISCV and related passageways. If when you removed the ISCV,
–
XJeff 97 XJ6L
New Bern, NC, United States
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In reply to a message from XJeff sent Tue 25 Sep 2007:
On the AJ6 engine (XJ40) you do set the gap at .002. Often, people
carry this forward to the AJ16 in their thinking. The TB’s on
these two engines are quite diffrent. There really is no way to
make this type of adjustment on an AJ16 TB.
Also, FWIW, the adjustment on the Throttle Cable on the AJ16 engine
is a mechanical carry-over from the AJ6. It did serve a purpose on
the early XJ40’s. On the X300, all it does is force an overide of
the electronic controls.–
The original message included these comments:
While it may appear that the butterfly is completely closed a small
gap is required and actually a critical adjustment. I seem to
recall (alldata?) from my idle wars, a static setting of .005’’ but
then final adjustment is required by scanning equipment able to
read IACV position. It is tempting to try to close this small gap
in cases of high idle but it is the amount of air allowed through
this small gap that references the IACV to the midpoint of it’s
range.
–
uncle
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In reply to a message from anthony davenport sent Tue 25 Sep 2007:
I have had the covers off a few times, and one of my friends bought
a new cam cover and it did not come with the gauze and baffle
plate, so we had to transfer the old one. You will note that the
studs that hold the plate in place are peaned over, so you must cut
them to remove the plate, once done, then you are left with how to
re-attach as the studs are now short. Even with a new cover (new
studs) we could find no good way to pean the studs.
So, the best soulution is to rinse/flush the old gunk out. Removing
the plate and the gauze is not practical.
I think if you did this very time you changed the cam cover gasket,
and cleared the vent hose and intake elbow every 30,000 miles or
so, you would have very little gunk build up in your TB.–
The original message included these comments:
not returned. What I suspect helped most was to thoroughly
clean the breather gauze in the cam cover. This is an easy
job but you’ll need to swill it out several times and let it
dry off completely before you re-fit it.You can clean and
re-gap the plugs while waiting? I wonder if anyone has
drilled out the rivets that hold the cover over the gauze
and made a more service-friendly arrangement?
Before you try removing the ISCV ,I suggest you research
–
uncle
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In reply to a message from Jagfan1986 sent Mon 24 Sep 2007:
Hi JagFan,
The primary function of the IACV is to regulate the air intake
at idle, when the butterfly is closed. If there is a significant
amount of carbon on the IACV, take it out again and clean it.
Also, make sure you clean the seat in which it sets, so that you
know there is a good seal. Just as with the throttle body, carbon
can build up here and hold the IACV open more than it should be.
Good luck with it.
Matt
'95 VDP–
The original message included these comments:
all. How is the car breathing to run with the throttle body closed
like that? This is starting to concern me. I removed the IACV and
it was coated in carbon (I didn’t clean it when I cleaned the TB),
so I wiped the carbon off of it and used a q-tip for the spaces I
couldn’t reach. After putting it back on the car and taking it for
–
Trilithon
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In reply to a message from uncle sent Tue 25 Sep 2007:
Doug,
I can’t imagine that your 95 is any different from my 97 but there
most certainly is an adjustment on mine. It is a small set screw -
maybe 1/2’’ long - against the stop tab on the top of the TB. The
screw is very small, hex or torx (no head) and pointed towards the
front/parallel to the engine.–
The original message included these comments:
these two engines are quite diffrent. There really is no way to
make this type of adjustment on an AJ16 TB.
–
XJeff 97 XJ6L
New Bern, NC, United States
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In reply to a message from XJeff sent Tue 25 Sep 2007:
Jeff you are correct. With that you can make a mechanical
adjustment to the throttle, but it is a holdover from the XJ40’s.
If you note on the bracket, you will also see an empty boss that
looks lke a second cable could be mounted. On the 88/89 Jags, the
transmissions had a mechanical kick down, and therefore a second
cable that used the boss and ran back to the transmission.
The point is there were a number of mechanical adjustmnents of the
XJ40 for the throttle, the transmission etc. That set screw was
used. Jag never changed the casting for the AJ16 engine.
You of course can use that screw to mechanocaly adjust the
throttle, but that is not what it is there for on the AJ16 engine.
One point of interest is that there is a mecahnical stop adjustment
that will prevent the throttle plate from opening past the 90
degree point. If out of adjustment you could open it further, there
fore restricting air flow, plus this can allow the thorttle to
stick open. I discovered this is a near catestrophic way.–
The original message included these comments:
I can’t imagine that your 95 is any different from my 97 but there
most certainly is an adjustment on mine. It is a small set screw -
maybe 1/2’’ long - against the stop tab on the top of the TB. The
screw is very small, hex or torx (no head) and pointed towards the
front/parallel to the engine.
–
uncle
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In reply to a message from Jagfan1986 sent Mon 24 Sep 2007:
Update: I got a friend today to help me test the IACV, and it did,
in fact, actuate when the ignition was turned on. However, when the
ignition was turned off, it shot the spring cover and valve off the
end of it. Is this normal? I know when it’s mounted on the car, the
seat won’t allow it to actually shoot the valve off the end of it,
so being out of the car could make a difference with that I
suppose. As for everything else, the IACV is clean, it’s seat is
clean, the TB is clean, and the butterfly appears to be in proper
adjustment. Any ideas?–
1996 Jaguar XJ6 VDP, 1993 Lincoln Mark VIII, & 1972 Lincoln
Salisbury, NC, United States
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In reply to a message from Jagfan1986 sent Tue 25 Sep 2007:
Hi JagFan,
Above, XJeff mentioned the set-screw. This screw on the '95
through '97 should be totally disengaged and not even touching the
stop on the cam. This is on the bottom of your throttle body, but
you should be able to see it while it is mounted. It is toward the
front of the engine, at least on mine.
I wouldn't suspect this though, since you did have your idle
down to normal once. I might also suggest disconnecting the
battery for 15 minutes, just in case it isn’t functioning
properly. Pay careful attention after you restart the car after
disconnecting it. The engine should not run well at first, and it
needs a good 30 minute drive to let it ‘re-learn’. When I do this,
I generally connect the positive and negative cables together after
about 5 minutes, when both are disconnected. I don’t recommend
this, but I am just telling you what I do.
I am having a hard time imagining that you had the idle down,
and now it is back up. This is a stranger problem than I could
think. I think resetting the computer could solve it, but cleaning
the body should have corrected it too. There is also a possibility
that you have a vaccuum leak. Check all of your circulation hoses,
and make sure they have a good seal. Also, check your air filter
and breather intake. It is rare, but you might have sucked up a
piece of plastic wrap that could be interferring with air-flow.
Other than that, I am tapped out. I can’t think of anything else
that could cause this.
On a brighter note, cleaning your throttle body was time well
spent, since it sounds like it needed it. A code-reader would
benefit you greatly right now. Since I got mine, things got alot
easier. It is very hard to diagnose problems these days when so
many things can contribute to the same symptoms. Make sure you
continue regular maintenance, and once this problem is solved, you
will reap many miles, I am sure. I hope this solves the problem,
and I again wish you luck with it.
Matt
'95 VDP–
The original message included these comments:
suppose. As for everything else, the IACV is clean, it’s seat is
clean, the TB is clean, and the butterfly appears to be in proper
–
Trilithon
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