Here's what I've tried so far and some diagnostics for you to read.

2005 XK8 4.2 Norm/Asp

68000 miles

Hesitation, 'juddering' during slow acceleration; Most prevalent @ 1500rpm with slow acceleration.

Active faults: P0191 & P0193 (Torque Pro APP with Bluetooth OBDII)

Starts well; Idles well; Wide Open Throttle = normal

30 day action report: Changed fuel filter (used model S filter initially using Forum recommendation. It has a smaller diameter) and cleared the codes. Engine ran normally for 30 minutes, then hesitation + P0191 & P0193 again. Fearing the new filter might be plugged with fuel tank contaminants, I posted the smaller-sized filter problem on the Forum and was advised NAPA Gold 3078 a perfect match to OEM for years 2003-2006. Thanks. I installed the new (perfect) filter, cleaned Fuel Rail Pressure Sensor (FRS) wiring harness, cleaned MAF sensor probe(s) and harness, did a ‘Hard Reset’ and the engine ran like a dream for 1 hour.

I tested the FRS with Digital Voltmeter: Key On, Engine Off (KOEO).

Harness off: U (blue) wire (signal?) + engine compartment ground: 5.01 V

OY wire (power?) + engine compartment ground: 5.01 V

BG wire (ground) + engine compartment Positive: 11.47 V

Harness on: U + (NEG) Online suggests normal should be 1.5 – 3V: 1.43 V

OY + (NEG) 5.01 V

BG + (POS) 11.39 V



Today I cleared the codes, did a ‘Hard Reset’ and logged fuel pressure readings in 60 second increments. Max APP readings seem to be 15.1 psi to 70.1 psi

Cold KOEO: 51.3, 50.5, 50.0, 49.8

Cold Start: 70.1, 52.0, 70.1, 58.0, 54.0, 61.8, 70.1, 64.0, 66.6, 70.1 (Engine Light ON right away today with Pending Code P0193)

Revs to 1600 rpm: 53.3, 67.3, 70.1, 45.3, 53.1, 58.7, 48.7

Revs to 3,000 rpm: 70.1, 50.9, 46. STOP ENGINE

Warm KOEO: 70.1, 48.7, 70.1, 49.2, 49.6, 70.1, 50.0

Some APP anomalies? While driving the App RPMs sometimes jump up to near 12,000 RPM. Fuel Press stuck at 70.1 even with ‘engine off and key off’ sometimes.
Well, what do you think?
Thanks

 

The reading off the sensor should be a pretty solid 55psi, never moving much. Have you checked the vacuum line to the sensor?

I'd say start with a good quality injector cleaner (Techron) now that you have a clean filter. Read the bottle and follow the directions. The cleaner should help clean the pop valve in the tank and restore normal behavior.

Best of luck, keep us posted.

 

Thanks fmertz. Will clean injectors tomorrow. I only glanced at upper area of FRS vacuum line, but will check top to bottom. Talk soon.

 

In particular, the DTC P0193 indicates an electrical fault rather than a faulty FPS or incorrect fuel pressure.

There is a description of an pinpoint test in the workshop manual that is designed to find short circuits or ground faults between the ECM and FPS.

I would download the WSM for my X100 and do the pinpoint test. That can be done with a multimeter, you have practice in that.

I also recommend to forget the torque app, get yourself an SDD V130 with a Mongoose Clone interface for diagnostic tasks. Or at least, get her checked with SDD.

Fritz

 

Thanks flatsix.
That's what I'm thinking too. What do you think of my FPS 'Signal' wire measuring 1.47 V KOEO? Normal?
After searching around the forum, I found a number of 4.2L owners (XK8, S-type) with a similar problem who solved it with a new 'Fuel Rail Pressure Sensor', which is also called the 'Jaguar Fuel Pressure Regulator' NTK AJ87977 on the website FCP Euro ($119 Cdn). Here's one post from CATMOBILE:

"I thought that I'd wait and see how the car drives for a while with the new fuel rail pressure sensor before I gave my verdict. The sensor was easy to replace, I ended up using Vaseline to lubricate the Orings. The Schradar valve was over some wires so I didn't want to mess with it, expecting gas spraying all over the place. After letting the car sit over night, the old one came out with no pressure left in the system. I got a NTK sensor, made by NGK and it works great. For anyone wanting to replace this sensor or any other, don't get a cheapo one! I think that most of the third party electronics on the car were originally Denso or NGK. No more P0193 codes and the throttle response is better and more consistent. The kick-down on the transmission works all the time, instead of once in awhile like before, I didn't expect it to affect that too. I guess that it's all tied together. It goes like a proper Jaag now.

__________________
2003 Jaguar S Type 4.2 Base
58,000 miles"

So I ordered the NTK part last night.
Flatsix, I'll hunt for that 'pinpoint test' you mentioned. Do you know where I might find it in the WSM? After I downloaded it, I can't seem to use the 'FIND' function.

I'll post updates.

 

The nominal voltage at the FPS output is between 0 and 5 volts, any value you like in between depending on the engine load. The voltage increases with the fuel pressure.

Of course, the FPS can also cause the problem. But if it is an electrical problem, replacing the FPS is useless. So my order would be to rule out electrical faults and then replace the FPS.

Fritz

 

Thanks Fritz. I'll keep hunting for that pinpoint test you were talking about.

 

Re: Pinpoint test... Found it. Workshop Manual years 2003-2006 pages 787, 1357 and 1358.
New IP sensor (FPS) arrives Monday. Techron in the tank after that and if still problematic, short circuit searches.
Thanks again.
Scott

 

SOLVED
It's a month since I received and installed the NKT AJ87977 Fuel Rail Pressure Sensor ($119 Cdn from FCP EURO). Very easy swap. Using advise from the forum, I placed a cloth below the FRS to catch the 2 non-metallic screws in case I dropped them. I used a blow-dryer to heat and then remove the vacuum hose, so as not to break it. I applied Lock-Tite 518 Instant Gasket to the new FRS and installed it.
KOEO: 55.4 PSI (Perfect). Started and drove car... 54-56 PSI under all driving inputs (Perfect). 3 'Pending' Fault Codes" P0191, P0193 and P1000... all good. Drove the car for an hour and unfortunately, on next start-up, P0193 now an Active Fault, but P0191 gone and P1000 indicating that OnBoard Monitoring Not Complete was still on... OK.
Performed a "HARD RESET". P0193 gone. Yay.
P1000 code evident for 6 hours of driving and then it switched to P1111 (= monitoring Tests Complete) Perfect.
One month later car continues to run great at 54-56 PSI steady.
Thanks all.
Scott

 

Well done. Always a pleasure to see that P1111 code....

 

Could you share more information on the location of the sensor and what needs to be removed to access it? How many labour hours? Thanks

 

You need to remove the plastic engine cover. 4 screws to twist 90 deg, as I remember. The sensor is "right there" at the end of the fuel rail. Everything is readily accessible. You are looking for the sensor with the vacuum line and the electrical connector (from memory, there is a fuel temp sensor as well, but no vacuum line on that one). Budget maybe an hour, but you will likely be done in less than half that. While you re there, double check the vacuum line for cracks/splits as well.

Remember, the sensor just reads the pressure with high precision, but only in a narrow range around 55 psi. The purpose is to drive the fuel pump PWM signal so the pump delivers precisely 55 psi. There is no returning fuel back to the tank like in a conventional system. This is done so the fuel is delivered in as exact quantities as required to reach the desired/mandated emissions levels. If the fuel pressure reading deviates too much from 55 psi, the sensor tops up (P0193) or bottoms down (P0191). The general understanding for P0193 is that the root cause is a failing pop valve at the pump. When the car is under some load and you suddenly close the throttle, the resulting excess fuel pressure is supposed to be released by that pop valve at the pump. If that pop valve is stuck, the pressure momentarily stays high and you get P0193. The sensor is rarely faulty (but I suppose cheap and easy enough to replace). That is why some effort should be spent on working that pop valve, say, with a reputable fuel cleaner. The pump assembly is (used to be?) very expensive and a lot more involved to replace, especially in the convertible.

Just my thoughts.

Best of luck, keep us posted.

 

Warning. I'm not a mechanic and did many hours of searching/reading to solve this problem.
1. Make sure fuel pressure is near zero
2. Remove plastic engine cover by removing oil cap + 4 screws
3. Heat/warm and remove rubber hose from Fuel Rail Pressure Sensor (FRPS)
4. Remove wiring harness from FRPS
5. Place a rag under FRPS to catch the 2 non-magnetic screws in case you drop them
6. Remove FRPS screws and FRPS.
7. Add the special 'grease' mentioned in my post to the FRPS and attach the new FRPS

Knowing what I now know, it's a 20 minute job and I'm slow!

 

fmertz. Very helpful info. Thank you!

 

Thank you !

 

I am having a tough time to confirm the use of NTk-FPC011 / AJ87977 / Ford #3R3E-9F972-AA / 3R3E-9F972-AB. Many sites say that these fit only upto 2004 for N.A S-type V8. S/C models are fine all the way
Has anyone used it on a 2006+ v8 N.A S-Type? Thanks

 

thanks. Do you mean the Additive Fuel cleaner that u put in the fuel tank?