Jaguar XJ-S. Service manual — part 78

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months ago.” Since grounds are a common cause of trouble in the Jaguar XJ-S, just go ahead and add a ground strap as
suggested on page 553.

FF67 -- SECONDARY AIR INJECTION SYSTEM: Charles Randle says, “My '94 6.0 started having FF67 set a
couple of months ago. I read up on it in the ROM, which tells me just enough to understand a dozen things that may
cause the problem. However, there is one ambiguous sentence that is a large gray area, so I took it to my local dealer
after talking to the Lead Technician on the phone. The simple things I could check myself I did. I determined the Air
was coming on and apparently in the right (as printed) sequences. The tech spent an hour verifying this on the JDS, and
called Mahwah. Two days later they faxed a "Decision Chart" and a possible problem/solution. It seems the PMCF on
all the 6.0's might have come from the factory with the PROM set too sensitive. During any of the secondary air
functions the PROM is looking for a certain voltage from both O2 Sensors. If it doesn't see a signal of this magnitude,
it sets FF67. And that is all it does. It doesn't go open loop or any other deregulating function. The bottom line is, the
dealer gave me the "Decision Chart" and said I really didn't want to pay him $78.00 an hour to verify 3 pages of
decision charts. He also gave me a mail for service procedure to send the PMCF to Delphi Diesel Systems for testing
and installation of a less sensitive PROM. To date I haven't either completed the Chart or contacted Delphi. The
JAGUAR NA procedure when the cars were under warranty was to have the dealer ship the PMCF to Mahwah, who
then sent it to Delphi and it was returned to the dealer COD for work/parts/shipping. For the time being, I am resigned
to ignoring the FF67 and dumping the code each time I won't be using the car for a while. There is no way to disable
the PMCF signal without disabling future serious codes that you might want to be notified of.”

Michael Hahne concurs: “My '94 XJ12 has the same FF67 deal. I replaced the O

2

sensors and had the recall done, and

it still shows up once in awhile. I talked with several knowledgeable folks who said it's probably clogged Air Injection
rails. It's a nasty job to clean these out, but hardly necessary for the kind of driving we do. It's mostly an emissions
thing. I've driven mine that way, occasionally clearing the FF67 code, for 10's of thousands of miles. No troubles. I
drive my '94 XJ12 from Chicago to New Orleans almost monthly. My car now has ~90,000 miles. I drive it daily to
and from work, a round trip of ~160 miles. Just drive the beast, and don't worry.”

FF69 -- DRIVE/NEUTRAL SWITCH: Alan Baker says, “This is a common fault on the XJ40's of that era, (they use
the same ECU). I'm told that the 'erroneous' Code 69 is caused by the battery voltage dropping too much during
cranking. It may be worth checking the battery terminals and connections for corrosion or possibly changing the battery
if it is of some age.”

Gregory Wells adds, “I was always told the FF69 involved the way the key is turned to start the car. If you grab the
key and turn it to the start position in one motion, the FF69 can be set. If you grab the key, turn it to the run position
and pause for just a brief moment before continuing on to the start position, the code won't set. I was told that the ECU
circuitry would not "see" the voltage level it was looking for if you passed through the run position quickly, rather than
pausing briefly, and this is what triggers the FF69 code.

“This isn't supposition, as we have many, many reports from customers that this procedure does keep the FF69 from
being set. The nice thing is that it costs nothing to try it.”

CLEARING FAULT CODES -- 6-CYL: Gary Penovich says, “On a ‘94, you can clear the fault code from the ECU
without disconnecting the battery. It's a piece of cake. Open the dash trim panel that's underneath the passenger airbag
by pulling down on it. Unscrew the passenger heater vent cover. Remove the small trim panel from around the heater
vent. You should see a purple connector attached to a yellow(?) wire. The connector has only one conductor in it, and
it isn't connected to anything. Short that conductor to ground for 3 seconds. It will clear the fault code. The process
may be the same for all AJ6 powered XJS, perhaps AJ16 as well.

“I have actually moved the connector outside of the trim by running the wire through the vent cover. Now, I can access
it simply by swinging the dash panel downward. It comes in handy after disconnecting sensors while the engine is
running. The ECU will flag a fault even if the key is on with the engine off!”

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Passing Emissions Tests

If your car is too old and tired to pass a required emissions test, you should have it corrected. However, if you don’t
have the time or money to get this done right now, John W. Himes makes the following suggestion: “I add a gallon of
denatured alcohol to the tank. This makes a very clean burning fuel. The car does not run as good with that in the tank,
but it passes emissions very well.”

Harry Trafford says, “I have used 99% isopropanol at 12% with some success. Brings down the CO%. Yes, the
percentage is high and the idle had to be adjusted to keep running, but these were desperate people. I had them add 46
oz. to make 3 gal. of premium. After the test, they just bought more gas to dilute the alcohol and readjust the idle.”

“I used 2-propanol because it’s what was available at the time. I also had methanol, but it’s corrosive and not a good
thing to put in British cars.”

Alcohol tends to be hard on some rubber products in the fuel systems of earlier cars, and British non-metallic parts have
enough trouble without adding to their woes. Therefore, it is not suggested that you use this method more often than
necessary.

Another idea used by some is to retard the timing a bit before the tests. You can’t retard the timing by turning the
distributor on a car with Marelli ignition, but Jaguar thoughtfully provided a jumper that can be pulled to operate the
Marelli ignition system on a slightly more retarded map.

Trafford continues, “I bought a CO analyzer, too. It’s a “Gunson’s Gastester”. This unit is not a professional system,
and you need a lot of patience because it must clear to 0 after you make any adjustment. Says it reads in 1 minute, but I
gave it more. It looks and feels cheap, but it worked for me by just following the directions. It’s made in England.”

“Here is the address for the guy that sells the “Gunson’s Gastester” CO analyzer in Pennsylvania. He will answer your
e-mail.

Ray at: r.d. enterprises, ltd.

290 Raub Road, Quakertown, PA 18951 USA

phone: +1 (215) 538-9323

fax: +1 (215) 538-0158

e-mail:

rdent@rdent.com

Fuel System Upgrades

CARBURETORS: Replacing the EFI with carburetors is not recommended. Carburetors have several disadvantages:
First, a standard carburetor does not correct for changes in altitude, temperature, fuel density, or other variables that
make an engine run at less than optimum performance. Corrections usually require an excessive amount of
complication in the carburetor design.

Second, since the carburetor relies on a pressure reduction due to drawing air through a venturi, there is always a flow
restriction due to the venturi. Using a carburetor with a larger venturi reduces the loss, but the airflow at idle is so small
that they have difficulty drawing fuel consistently, and a rough idle and poor low speed performance is the result. The
American solution was the progressive 4-barrel, which uses one set of venturis at low speed and an additional set at
high speed.

Third, carburetors tend to have problems ensuring proper fuel/air mixtures at all cylinders. With most arrangements,
the corner cylinders on a V-8 tend to run leaner, because the path for the fuel/air mixture to get to them is more

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convoluted, and the fuel gets left behind and drawn into a nearer cylinder. Such problems would be even more serious
on a V12.

Problems occur when a cylinder runs lean; burned pistons usually result. In the old days, the engines would simply be
adjusted rich enough to avoid any problems. When environmental regulations and fuel efficiency demands rendered
this solution unacceptable, the incidence of burned pistons increased.

The time-honored solution to this problem was multiple carburetor systems. The intake path for each cylinder must be
similar, and sometimes even a dedicated barrel for each cylinder was used (Webers, etc.).

Obviously, fixing all these problems simultaneously would involve a truly elaborate carburetor system, possibly
requiring multiple, progressive barrels for each cylinder.

EFI systems generally come in two types: throttle-body and multi-port. Each type will correct the first and second
problem of carburetors, because all EFI systems automatically correct for variables and no EFI requires a venturi. The
throttle-body system, which consists of a single injector in the same housing as the butterfly valve, shares the same
distribution problems as carburetors, but is much simpler and cheaper than multi-port.

Multi-port EFI, what the Jaguar comes with, is the ideal fuel supply system. Since the injectors serve each cylinder
individually, there is little chance of a cylinder not getting its share.

The only disadvantage of EFI is the difficulty in modifying it -- which, of course, the EPA considers an advantage.
However, contacting AJ6 Engineering (see page 710) will likely alleviate all such concerns; they will modify ECU’s
for very reasonable fees.

EFI SYSTEM REPLACEMENT: Electromotive Inc. (see page 713) makes a system called the TEC-I (TEC stands for
Total Engine Control) that replaces the EFI computer and the entire ignition system as well. It’s got more modern and
comprehensive electronics than the Jaguar original, including an optional knock sensor. Also, it is programmable using
a PC-compatible computer, allowing the owner to customize the operation to suit his needs. It’s not cheap; but if your
ECU has already died and you’re looking at the cost of the Jag original to get running again, it starts to look cheaper.
And if you’re having ignition problems as well (this system renders the entire distributor superfluous, you might as well
put in a blank-off plate), it starts to look downright reasonable.

If you are performing serious engine modifications, this system is just the ticket. Since it can be calibrated, you are not
restricted to the original response curves on your non-stock engine.

AJ6 Engineering (see page 710) also makes replacement EFI systems and components, and will modify the stock ECU
on an exchange basis. According to Jeffrey Gram, “if experimenting was wished they could do a single EPROM
version , which has up to 8 MAPs. It would be possible to switch between the MAPs if the ECU is depowered between
switches by means of a “dial”. AJ6 do such programmes to experimenters which then have 8 maps to choose from
trying to find the best setting.”

Scott Horner found an aftermarket system in New Zealand:

Link

Electro

243D

Annex

Rd

Christchurch, ph +64 3 348-8854

“From them you can buy the ECU, Ignitors, Injector Ballast and Tuning Module (a handheld LCD interface) & the
Crank Angle Sensor... You still need to supply a lambda sensor (aftermarket Bosch will do), and the coils...On my car,
we used VN Holden Commodore (Australian GM car) coils, 2 coil packs. The Holden uses the Buick 3.8 liter engine,
so it’s presumable the coils would be available in the US in some form. I have heard these coils only last about
20,000km, but we’ll see.

“Any 3 or 6 pack coil combination would do, I have heard Audi have a very tidy solution...”

Robert Dingli reports: “Here in Australia there are many, many aftermarket injection ECU’s available. I’ve tested
many of them in cars and on the bench and have found most of them to be garbage. Common faults are production

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quality, lack of temperature compensation and other instabilities, and general difficulties with setting up a system from
scratch. Basically you get what you pay for. A $2000 Motec or Autronics unit is highly recommended over sub-$1000
Injec, Linx EMX, Microtec or Haltec. The expensive units also control ignition. The Motec, Autronics and Haltec
require a portable PC (to be added to the cost if not available) to make proper adjustments.

“As far as “high performance” chips are concerned, I’m rather skeptical as to their worth. The problem (??) with
modern day EFI systems is that they are very close to optimum, being a fine balance of performance, economy and
exhaust emissions. Some of the chips available advertise that the systems will still comply with pollution levels. The
specs reveal that power increases are only in the order of a few percent for most cars.”

“Systems where chip changes may actually make a noticeable difference are:

-

Systems with electronically-governed rev limits.

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Racing use where pollution isn’t a concern.

-

Turbo cars where the electronically-governed boost limits are raised.

-

Electronic ignition systems without knock sensors where the timing maps can be advanced to take advantage
of better quality fuels.

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Electronically-controlled auto gearboxes where upshift points are raised.

-

Older poorly-calibrated systems, e.g. SIII XJ6 Jags set up for cold climates but being run in warmer climates.”

According to Ken Wallace, “If you live in a regulated area the smog police will not approve of any of this even if it
improves your emissions. You can have your installation certified, but this is very expensive like more than $10,000
from what I hear.”

Robert Gee adds a warning about aftermarket EFI systems: “I worked for a car manufacturer who made their own
injection systems (Rover MEMS). One or two people had fitted MEMS to their own cars, mostly for competition use.
One guy had a modified peugeot 205 GTi with one in. He had spent a fortune on the thing.

“Now, given that this guy had access to rolling roads, vehicle calibration experts and the like, the driveability was never
perfect (an important Jaguar feature - low throttle response crucial on an auto). Also he went through about 3-4
tankfuls of petrol doing the calibration (not too bad at US petrol prices I suppose - more than the cost of an ECU at UK
prices). And this was still with the very fine tuning carried out automatically (This was done with some special
adaptive software we were working on which used the lambda sensor feedback signals to adjust the fuelling maps).

“To cap it all, when he came to sell the car it was quite hard since it was non-standard and hence not supported by any
garages.

“Put it this way, I could have converted my XJ-S 3.6 to full sequential injection with fully programmed ignition for next
to no cost - but preferred to keep it standard and I probably would not have got it any better than the Lucas P digital.

“If there one thing I learn't at Rover it’s that the low throttle drivability is what separates a good car from a bad one -
and it also takes about 95% of the engineering effort. Anybody can make a car which goes well at full throttle - and I
suspect it’s the latter market at which the after market fuel injection systems are aimed.”

FUEL INJECTOR ORIENTATION: Strictly a cuteness mod here. Of the 12 fuel injectors on the XJ-S, some have the
electrical connector pointing rearward and some have it pointing forward. If you wish, it is possible to reorient any fuel
injector to point either rearwards or forwards, even the two front ones -- the connector will easily fit under the arc of the
fuel hose.

To reverse the orientation of an injector is not easy unless you happen to be replacing the hoses or the rubber seals, in
which case it’s a snap. While the large rubber seal is off or the hose is disconnected, take the plate that retains the
injector off and flip it over. Twist the injector around on the hose. The wiring harness will usually reach either side of
an injector, but note that some harnesses are really brittle and fiddling with stuff like this may be asking for trouble.