[xj-s] Fuel Fail 13 code, '92 XJS V12

Similar to Philip’s XJS, my '92 has been providing me with reliable
service. Since putting it back on the road about two months ago
(after its winter hibernation), I have put approximately 3,500
miles on it. Other than the electric cooling fans going out on me
(I knew this was going to happen, and just hadn’t replaced them
over the winter), the car has been running perfectly. I put some
Derale cooling fans on and now the thing will idle on hot days with
the AC on and not complain.

But one can never relax entirely with these cars. Yesterday on the
drive home from work the check engine light came on. I am getting a
code Fuel Fail 13, for which I can not find an explanation. Unlike
most FF codes, this one appears to have a running issue associated
with it. Specifically, the car acts somewhat like it thinks the
engine is still cold in terms of when it shuts off fuel to the
injectors whilst coasting. Normally once warm, it shuts off fuel
when I let off the throttle until somewhere around 1000 RPMs. Now
it seems to be 1500 RPM or so, which is what I normally observe
when the engine is cold.

I haven’t checked anything yet, I first wanted to know if anyone
has an idea what this code means!

-Ted – '92 XJS V12 5-speed
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In reply to a message from TedDuPuis sent Wed 28 May 2008:

The FF13 is failure of the MAP sensor, which is located in the ECU.
However it can be triggered by a variety of things. Essentially it
has sensed low vacuum at low rpm on a closed throttle (when vacuum
should be high). I had the FF13 readout.
It turned out the RH cylinder bank had failed, due to a grounded
rotor. the car would just barely run.
Once the cap and rotor were replaced, the car ran fine and the FF13
code went away.
I would think a vacuum leak could cause the code to appear.
(Map signal less than 80Torr at less than 1500rpm, code will be set.
Map signal less than 550Torr at less than 1000rpm, code will be set.
check inhibited below 350rpm). that is what manual says.
I haven’t referenced Torr against Hg of vacuum; but it seems
obvious that getting a too-low vacuum reading is what causes it to
come on. A leak in the pipe going to the ECU in the trunk might do
it, too.–
The original message included these comments:

code Fuel Fail 13, for which I can not find an explanation. Unlike

Facelift 5.3L V12, 4.0L Coupe
st petersburg florida, United States
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