On my 2003 XJR I can't seem to shake P0300, P0301, P0302, etc up to P0308 and lastly P1316. When reset it will run for twenty-five to maybe seventy-five miles and throw these same codes. The car does not have any misfiring going on that I can tell. It starts immediately and idles smoothly without a stumble, The code pops up sometimes when idling or driving at any particular speed, warm or cold.
I recently removed the blower and replace the knock sensor and water hoses, installed new Bosch plugs, and replaced the valve covers. The engine has about 150K miles and is very clean inside; cleanest I have encountered with my other 308 Jaguars. I cannot imagine what is causing this. I cleaned the MAF sensor which made no difference.
One thing I see that seems strange, the fuel trims are weirdly high. Short trims are 129% and long trims are 139% for both banks respectively. If this indicates a vacuum leak the I'd expect to get a CEL warning about that. Are these trims normal on XJRs? If not, where could the vacuum leaks be coming from or what could cause these level of readings? The cars runs great and accelerates quickly and smoothly.


I'm sorta stumped.....have always managed to fix weird CEL warnings on my NA jags but this SC car adds a bit of complexity.

Any advice would be certainly appreciated!

 

weird stuff..could be a dying ecm

check your fuel trims with another tool

 

Will do that and report back. I hope the ECM is not hosed! That would be a huge problem. If it is, would an ECM from a 2000 VDP be a candidate for a reflash?

 

There is a small vacuum hose that connects to the RH side of the supercharger. It's visible from the top, but it is nested between the intercooler and the sc body so it's not super obvious. That little hose may have gotten knocked off, or maybe you forgot to reconnect it. I had that same problem, which is why I'm suggesting it. I was getting lean codes all the time.

 

I had the same problem a year ago and it turned out to be the alternator; it wasn't producing enough current to run the electronics. The short story: I was on a trip and on day four the P03XX codes started showing up, just for the day. I had two scanners with me, so cleared the codes and pressed on. On day six, I got the IAT-2 code four times; reset and pressed on again and didn't see that code anymore. On day eight, the P03XX started showing up again. One more day to get home and the car had no problems. One of my neighbors is an electronics engineer so I had him take a look. I hooked up my Autel scanner and the first thing he noticed was the voltage was at 12.6 and didn't move when I started the engine. The voltage needs to be 13.5 to 14.5 to run all the stuff. Replaced the alternator and no more codes. But wait, there's more! A couple weeks after the new alternator I got the codes for both banks being too rich. With the electrical system being fixed I believed those codes as the car was at 190k miles. Replaced the Fuel Pressure Regulator and that problem was solved. Since the OEM FPR is no longer available, other than used from a junk yard, I put in an Aeromotive adjustable FPR. Car's been running fine since.

 

Here's the thread for adjustable FPR install: https://www.jaguarforums.com/forum/x...anyone-186369/

And I've attached a piece written by another forum member for checking the voltages.

 

Yes...a weak or bad alternator shows itself in multiple ways.

 

That is great advice! I will start with the fuel by replacing the fuel pressure regulator and see if that clears the codes. If not, the alternator will be next. BTW: we have had company at the house for that past few days so have not been fooling with the car though I have driven it about 135 miles with no codes so hope to at least get is inspected before it might throw another code...
Also, I checked the the short term and long term fuel trims and they are reading within normal ranges now, (About -1.87 and -2,36 short and about -85 long term for each.) the car runs great too! I will replace the fuel pressure regulator and check the alternator voltage anyway and replace as indicated.
THANKS MUCH for the advice! You guys are the best!

 

Just a heads up about the adjustable fpr route, I was never able to get it to adjust properly between idle and wot. It would run fine at lower rpm but at speed it would throw rich codes. I wound up switching back to an oem fpr and have been trouble free since. I’ll post the same in my original thread so others don’t assume it’s a straightforward fix.

 

That is a truly a comprehensive trouble-shooting guide and nicely illustrated! Huge thanks to avt007, AKA rob..
I also had a weak braided ground cable to negative connector problem on my first 2000 red VDP and also soldered it massively to repair! I'm going to go through the whole thing with my XJR and hope I can find and fix the problems. Thanks a bunch guys!

WIll let everyone know if the DTC codes are finally banished.

Also, a while back I posted some weird fuel trim numbers and a second test that was somewhat more normal. Yesterday and this morning I checked and the numbers were much better; close to zero. I am wondering if the strange readings are related to the problem? Of course even with normal trims the car throws the same codes. More later....

 

k-man - that's interesting; I set mine at 41psi at idle, shut the bonnet, and haven't had any problems. I don't know if this makes any difference, but when I installed mine, I had the SC off, so I was able to run the return line under the intake elbow. I couldn't tell by your pictures how you ran yours. Anyway, I thought that you had come up with the perfect solution to the FPR problem!.

 

Highspeed42- Oh that’s awesome that it worked, means the problem must have been on my end. It’s been so long I don’t remember exactly how I set it up but now I might have to revisit the Aeromotive fpr

 

I found this problem while checking voltages. Fixed this but the codes came back! Another day at home to work on the car,,,,,more later

 

This may be a simplistic post, however that approach is what is needed when chasing strange misfires.
There are three major areas which can cause the noted misfires.

The ignition system, which is responsible for creating and delivering spark.
The fuel system, which is responsible for supplying each engine cylinder with fuel.
Internal engine parts, specifically piston rings, cylinder head valves, intake manifold gaskets
(these are responsible for the air part of the air, fuel, and spark mixture).In most cases, it's usually a lack of spark that's to blame for the misfire, but not always.
Ignition System: If any one engine cylinder is not getting spark, then you'll have a bonafide misfire on your hands.
The following ignition system components could cause a misfire when they fail:

1. Bad COP (Coil-On-Plug) ignition coil.
2. Broken COP ignition coil connector (this is a very, very common problem).
3. Bad coil pack
4. Bad spark plug or spark plugs
5. Bad ignition coil boot (on COP ignition coil systems).
6. Carbon tracks on the spark plug and spark plug boot.
7. Bad spark plug wires (if your engine has a coil pack ignition system).

The good news is that all of the components that make up the ignition system can be tested,

Fuel System: If fuel is missing from any one specific engine cylinder, it will misfire.

The following fuel system components could cause a misfire when they fail:

1. Bad fuel injectors.
2. Electrical short in the fuel injector wires that are keeping the fuel injector pulse signal from reaching the fuel injector.
3. Broken fuel injector connector (this is a very, very common problem).
4. Bad PCM (this is very rare, but it does happen).

Engine Mechanical Condition: This is one of the most overlooked conditions when testing for a misfire.

The following engine mechanical problems could cause a misfire:

1. An engine cylinder that is not producing enough compression.
   • Even it has the spark and fuel, but the compression is low, that cylinder will misfire and set a misfire code.
2. Another thing that will cause a misfire (normally at idle) is vacuum leaks coming from a large vacuum hose or the intake manifold gasket.
   • intake manifold gaskets (spark plug wells).

 

Dave - that wire looks like it got pretty hot; what did you do to fix it? And, once fixed, did you check the voltage at the false bulkhead? That's the wire powering everything.

K-man - Yea, I would try it again. A disclaimer to my statement/experience with the setup: I haven't done a live data run since I put that FPR in (shortly after your first post), and I haven't seen any CELs for rich banks, either. And, I do drive the car pretty aggressive. One thing I noticed from the install instructions is that these things will increase the fuel pressure 1 to 1 to manifold pressure; increases with boost and decreases with vacuum. There's another statement that reads, "Aeromotive system components are not legal for sale or use on emission controlled motor vehicles." I haven't figured out that one, yet. Another factor that might affect my setup versus yours is the mods I've done. So far, I've got the Eurotoys intercooler radiator and Bosch pump, oversized lower SC pulley, the latest Mina Gallery intake tube, Nameless downpipes with 200 cell cats, and upgraded transmission valve body stuff with AMG blue top shift solenoids. That's all I remember right now without going out and looking. The car runs great for 190k miles on it.

Randy - good refresher on the mechanical portion. I'm concerned about Dave's burnt up power cable.

 

Hello Guys,
The nut on that particular high amperage connection was very loose so I suspect it was not tight for a long time and got hot and melted the plastic inside the nut. I removed the fuse and cable and sanded off the dark film from the fuse and cable end and reconnected using a nut from a crashed XJ that I'm removing parts from, The voltage on the bulkhead connector it 13.89v with the car running so I'm not thinking the problems is low current/voltage. x

One of my OBD testers has a mode to monitor the car and take a snapshot if it throws a DTC code. The fuel system monitors are what it is tripping the OBD code so hence the regulator replacement. Hello Guys,
The nut on that particular high amperage connection was very loose so I suspect it was not tight for a long time and got hot and melted the plastic inside the nut. I removed the fuse and cable and sanded off the dark film from the fuse and cable end and reconnected using a nut from a crashed XJ that I'm removing parts from, The voltage on the bulkhead connector it 13.89v with the car running so I'm not thinking the problems is low current/voltage.
One of my OBD testers has a mode to monitor the car and take a snapshot if it throws a DTC code. It showed the fuel system monitors are what it is tripping the code. At this point I have a new pressure regulator on order and will replace it next week to see if the fuel problems are resolved. Fingers crossed! Will fill you in in either case....Best, Dave


BTW: very comprehensive explanation on the operation of the engine systems RandyS Much appreciated you wordsmith!

 

I ordered a fuel pressure regulator that claimed it would fit the type with the two bolts; however, it is a regulator for a NA 308 XJ8 and certainly would not fit my car. When searching for a correct one, I've found a few that look corect with fuel pipe attached for about $245.00 but are out of stock. I suppose I could ask the dealer next week when they are open, (today is Saturday), but I'd suspect the price to be even higher. Any idea when I could get one or does everyone give up and install the external unit as hispeed42 did on his car?
The unit received.... Not the right one I'm quite sure....

 

The Jaguar part JLM21358 is available from several places on the internet.

All AJ27 engines should use this part number. (X100 and X308)

 

Bob, isn't that the part number for NA engines? The SC FPR was NCA3007CA; however, the parts catalogue that I have, from 2017, states that this part is only available as a fuel return line. I ordered one a few years ago and got what looked like an FPR for an SC engine attached to a short return line that looks like the one for the NA engine. There's another part number listed for the fuel return pipe, AJ81480.

I did a little Googlin' this morning and came across a parts catalogue for early XKs. This one shows all three FPR setups on one page, and it appears that the FPR that I got was for early NA 4.0 engines. It's in the diagram in the upper right of the attachment. It appears that the FPR that Dave got is for an NA engine in the lower diagram, and what we need is in the upper left diagram.

Anyway, from what I've found over the years looking for an OEM FPR for an SC engine is that they're only available as used parts, so I went with the mod.

 

YES that is the NA part.(did not notice the XJR reference)