[xj] V12 will not rev over 2000rpm while in gear

After getting the car back from the transmission shop, the
car will not rev over 2000rpm while in Drive, regardless of
the gear. It starts immediately, runs smoothly and has
power until 2000rpm when it hits a wall and drops back down
to 1500rpm.

The car has just had extensive mechanical work done
including new fuel filter, new fuel tanks, new (Jaguar) fuel
pump, flowed/cleaned injectors and new hose, both fuel
pressure regulators, new distributor, leads, plugs. None of
the usual ‘‘no power’’ culprits.

In Neutral or Park, the engine revs freely.

Any ideas would be great…
-Chris–
Chris Los 1989 V12 Vanden Plas
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Are you saying that you could take it to redline in park or neutral, but
not in drive? In drive will the car move, but not over 2000 RPM? In
theory then, that limits you to 80 km/h?

Craig

thetopdogg wrote:>After getting the car back from the transmission shop, the

car will not rev over 2000rpm while in Drive,

In Neutral or Park, the engine revs freely.

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Maybe one of the coils is bad, causing very weak spark that can’t
light the rich mixture under load.On 18 Jul 2008, at 20:05, thetopdogg wrote:

After getting the car back from the transmission shop, the
car will not rev over 2000rpm while in Drive, regardless of
the gear. It starts immediately, runs smoothly and has
power until 2000rpm when it hits a wall and drops back down
to 1500rpm.

The car has just had extensive mechanical work done
including new fuel filter, new fuel tanks, new (Jaguar) fuel
pump, flowed/cleaned injectors and new hose, both fuel
pressure regulators, new distributor, leads, plugs. None of
the usual ‘‘no power’’ culprits.

In Neutral or Park, the engine revs freely.

Any ideas would be great…


Justin Hill, Surrey UK
Jaguar XJ12 HE 1982 “The Cuckoo”
Jaguar XJ40 4.0 1989 but actually a 1990 model year specification
Sovereign VIN 605518 “Horn Rimmed Harry”
Land Rover SIII SWB 1980 2.25 Diesel “The Biscuit Tin”
@Justin_Hill1

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In reply to a message from Craig Talbot sent Fri 18 Jul 2008:

Yes Craig, that is correct. I drove it about 50km after
having the vaccuum line replaced, and everything worked
properly. Then, Karen took the car out for the evening and
on the way back said she had trouble getting up to highway
speed (75km/hr, the way she drives!) and when she was almost
home, the car stalled going around a corner (presumably as
she was accelerating out of it.)

I did a road test and found that it drives as normal so long
as you don’t rev over 2000rpm, however when I parked it, I
could rev to the redline with no trouble at all, in both P
and N. I don’t have the space or courage to do the same
redline test in ‘R’ :slight_smile:

-Chris–
The original message included these comments:

Are you saying that you could take it to redline in park or neutral, but
not in drive? In drive will the car move, but not over 2000 RPM? In
theory then, that limits you to 80 km/h?


Chris Los 1989 V12 Vanden Plas
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That’s an interesting problem. It sounds like the symptoms of a plugged
fuel filter, and considering the amount of work you’ve done to the fuel
system it might be a good idea to change it again. Perhaps you’ve
disturbed a pocket of crud, or just got a load of bad gas and that’s
causing the problem? I had a friends van that had similar symptoms, but
would only get to 50 km/h, and it was a bunch of rust from the fuel. I
changed the filter and all was well.

At least changing the filter is relatively easy to do, just a bit messy.
The symptoms point to fuel starvation in some way.

Craig>

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FWIW, I second the fuel filter suggestion.

Chris…When it reaches the brick wall of 2000 rpm does it buck and jerk
and carry on, or just go “blahhhh”?

Cheers

Doug Dwyer
Longview Washington USA
1995 XJR
1990 T-Bird SCFrom: “Craig Talbot” talbotc@telus.net

That’s an interesting problem. It sounds like the symptoms of a plugged
fuel filter, and considering the amount of work you’ve done to the fuel
system it might be a good idea to change it again. Perhaps you’ve
disturbed a pocket of crud, or just got a load of bad gas and that’s
causing the problem? I had a friends van that had similar symptoms, but
would only get to 50 km/h, and it was a bunch of rust from the fuel. I
changed the filter and all was well.

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Chris,

Is your a Lucas or Marelli ignition car? Either way, check to see if
BOTH coils are firing. If it is Marelli and one side is out PARK THE
CAR!!! The raw, unburned gas will continue to accumulate in the cat
until it catches fire. Not to mention it will destroy the cat if it
doesn’t burn.

If it is a Lucas car, I’m certain you are aware of the second coil
mounted behind the grill. Make certain it too is properly connected
and functioning. I doubt that this is the problem as they will usually
fire up to about 4,000 rpm before going flat.

Keep us advised of what you find and we’ll go from there if the problem
isn’t corrected by the above. One of us here will find it!

Earl in Houston===================================================
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All Series 3 cars kept Lucas until the end in 1992.

Craig

Earl Kiker wrote:>Chris,

Is your a Lucas or Marelli ignition car?

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In reply to a message from Doug Dwyer sent Sat 19 Jul 2008:

When I give it some throttle and it gets to 2000rpm or so it
feels like its leaning out (aka more air through the
throttle but not any increase in fuel) very quickly, and if
I keep the gas down the revs will drop to 500 or lower, when
I let up on the gas the revs resume.
It is definetly a fuel problem; I turned off the car for
about 5 minutes while in the store, and when I came out it
turned over and caught, but died right away. I left the key
in ‘‘On’’ for about 3 minutes, and this time it caught, then
stumbled for a minute or so, then gradually the revs came up
to about 700. I was then able to drive the car, albeit with
the 2000rpm limit.

On the highway in 3rd gear, I was able to ease the car up to
about 2500rpm and about 95km/hr if I pressed the pedal very
very gently.

I will replace the (500km old) fuel filter tomorrow. If
that doesn’t work, what’s next? Fuel pump? (also 500km
old)

-Chris–
The original message included these comments:

FWIW, I second the fuel filter suggestion.
Chris…When it reaches the brick wall of 2000 rpm does it buck and jerk
and carry on, or just go ‘‘blahhhh’’?


Chris Los 1989 V12 Vanden Plas
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In reply to a message from thetopdogg sent Sat 19 Jul 2008:

When you remove the fuel filter, tap the inlet end onto a white
piece of paper and see what comes out. If you see reddish crud,
you have rusty tanks. The symptoms you describe are similar to
what I experienced a few years ago with my XJ6 except in my case
there was definite fuel starvation and backfiring through the
intake side.

My filter and pump were packed with crud and both had to be
replaced. I drained the tanks and added an in-line fuel filter on
either side of the changeover valve. (See photo) These little
filters are a lot cheaper than another new fuel pump! Someday I’ll
tackle the task of replacing the tanks, but in the meantime, the
little filters seem to be doing their job nicely.

The lack of backfiring or bucking confuses me a bit however. BTW, I
could keep my car running as long as I didn’t accelerate and this
was especially true when turning a corner, as you mentioned.

http://www.jag-lovers.org/snaps/snap_view.php3?id=1103397627--
The original message included these comments:

I will replace the (500km old) fuel filter tomorrow. If
that doesn’t work, what’s next? Fuel pump? (also 500km
old)


Bruce Hugo '80 XJ6 SIII
St. Helens, OR, United States
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In reply to a message from Bruce Hugo sent Sat 19 Jul 2008:

I have brand new fuel tanks, so this seems unlikely. I will
be changing the filter tomorrow, or at least blowing it out to
see what is in there.
There is no backfiring or bucking whatsoever, and believe me,
I know what THAT sounds like!

-Chris–
The original message included these comments:

When you remove the fuel filter, tap the inlet end onto a white
piece of paper and see what comes out. If you see reddish crud,
you have rusty tanks. The symptoms you describe are similar to
what I experienced a few years ago with my XJ6 except in my case
there was definite fuel starvation and backfiring through the
intake side.


Chris Los 1989 V12 Vanden Plas
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I don’t think you’d see much by blowing it out. Let it dry for a few
days and the cut it open to see what’s in the filter paper.

Craig

thetopdogg wrote:> I will be changing the filter tomorrow, or at least blowing it out to

see what is in there.

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thetopdogg wrote:

In reply to a message from Bruce Hugo sent Sat 19 Jul 2008:

I have brand new fuel tanks, so this seems unlikely. I will
be changing the filter tomorrow, or at least blowing it out to
see what is in there.
There is no backfiring or bucking whatsoever, and believe me,
I know what THAT sounds like!

Which is the oddity, Chris - with leaning out due to insufficient fuel
one would expect backfiring…:slight_smile:

In principle fuel starvation would be observable when monitoring fuel
pressure. It’s somewhat difficult while driving and as the engine revs
normally while stionary in idle it’s a bit awkward. You could check fuel
pressure while in gear, in effect running a stall test. This will give
a high fuel demand which should show up as a serious drop in fuel
pressure. If the engine shows the same recalcitrance to rev to the
spec’ed stall speed and the fuel pressure remains normal - it ain’t fuel…

While driving there is a higher power demand on the engine than in
neutral - increasing with speed and particularely during acceleration.
Given the somewhat complicated vacuum/ignition set-up of the V12 this
may equally be an ign/ ign timing problem. Without proper reaction of
the ign timing to vacuum, and insufficient capacity to overcome the
higher cylinder pressures under load, the engine may falter…

Frank
xj6 85 Sov Europe (UK/NZ)===================================================
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In reply to a message from thetopdogg sent Fri 18 Jul 2008:

‘’…did a road test and found that it drives as normal so long
as you don’t rev over 2000rpm, however when I parked it, I
could rev to the redline with no trouble at all, in both P
and N.’’

Revving in neutral doesn’t say much about the settngs, as there is
no load. Can you hold it at high revs rather than blip it? Not
suggesting you trash your engine of course, but it should be OK at,
say, 4K in neutral for 5-10 seconds to check if it holds steady
without misfiring, which is different from just reaching the red
line on a blip.

Pete–
66 2+2, 68 OTS lump, 94 X300 Sovereign, 94 XJR Manual
Cambridge, United Kingdom
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In reply to a message from Frank Andersen sent Sat 19 Jul 2008:

Chris:

Gotta find a way to check ignition and fusel under load and with
open throttle.

  1. Since the bonnett opens forward, a fuel pressure guage could be
    instslled and taped in such a way so as to be visible from the
    cabin. Then replicate driving conditions that show the issue. If
    fuel pressure is low, you are there.

  2. Now as to ignition, if fuel ps is good, then as frank suggests,
    run a stall test . But, the problem remains as to how to measure
    spark quality. I seem to recall a device that culd be placed in
    series on an HT lead and observe the spark quality. Probably only
    good enough to see if there was any atall.

I wonder if a really good tune up shop would have the diagnostic
equipment to measure spark quality under load.

So, if you could isolate to fuel or spark, then go from there.

Carl–
Carl Hutchins 1983 Jaguar XJ6 with LT1 and 1994 Jeep Grand
Walnut Creek, California, United States
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I know I’m a small voice among more experienced minds but I do own a
V12 and I have had similar problems. As per my original post: have
you confirmed that both coils are connected and working properly? My
own V12 has had a similar problem- caused by a duff aux coil.

JustinOn 19 Jul 2008, at 02:53, thetopdogg wrote:

It is definetly a fuel problem; I turned off the car for
about 5 minutes while in the store, and when I came out it
turned over and caught, but died right away. I left the key
in ‘‘On’’ for about 3 minutes, and this time it caught, then
stumbled for a minute or so, then gradually the revs came up
to about 700. I was then able to drive the car, albeit with
the 2000rpm limit.


Justin Hill, Surrey UK
Jaguar XJ12 HE 1982 “The Cuckoo”
Jaguar XJ40 4.0 1989 but actually a 1990 model year specification
Sovereign VIN 605518 “Horn Rimmed Harry”
Land Rover SIII SWB 1980 2.25 Diesel “The Biscuit Tin”
@Justin_Hill1

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Chris, you should try blowing through the filter by mouth when you have
it out – a good one will be very easy to blow through. If it’s not,
cover the input end and fill it’s engine-side end with acetone. Let it
run out the input end the next day, into a pot, and see what comes out.–
Alex
79xj6L SII (BRG + wires)
86xj6 SIII (Black)
61 Sprite MkII (Red)
Menlo Park, Calif.

thetopdogg wrote:

In reply to a message from Bruce Hugo sent Sat 19 Jul 2008:

I have brand new fuel tanks, so this seems unlikely. I will
be changing the filter tomorrow, or at least blowing it out to
see what is in there.
There is no backfiring or bucking whatsoever, and believe me,
I know what THAT sounds like!

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In reply to a message from Bruce Hugo sent Sat 19 Jul 2008:

had the same problem with crud in the tanks.stuff gets caught in
the pick-ups insude the tanks.i had to drain tank completely.fixed
the problem though.
brett 1987 vdp–
wesley64
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