My 2007 Jaguar XKR has about 130k miles on it. For the last month or two it runs rough at times and then throws codes. The codes are not that consistent (fuel rail, cruise control, crankshaft, camshaft). I charge the battery overnight, clear the codes and then it runs fine for a while, sometimes weeks without throwing codes. The other day it was running rough and then stalled several times while I drove it home. It seems like the rough running is happening more frequently between charges although I am not 100% sure of that.

I read some articles here and saw the suggestions that there might be an electrical drain somewhere. When charged the battery shows 12.4 - 12.8 volts and when running the voltage is 14+. It starts every time without issue. It often starts running rough after I have driven it a few miles.

I brought it to the mechanic yesterday and today he said it was fine, no issues. He said an electrical drain would have to be large and would stop the car from starting at times. He tested the battery and the alternator and cleared the codes. He ran it and found no codes that indicated any electrical problem or other problem. I told him I was sure it was not fine, that it might take a day or 2 weeks to run rough but that it was happening consistently. He said he will run more tests. They do European cars but more German than English.

Any insights would be appreciated (other than get a new mechanic). I listed the dates and the codes I have seen below.

Biff

You can try disconnecting the battery for 15 minutes and touching the positive and negative battery cables together to drain the capacitors in case it just needs a reset. If it persists then further diagnosis will be needed.

Thanks. I will try that.

Intermittent issues like that can be due to one or both fuel pumps being on the blink and/or the fuel pressure regulator depending upon which engine you have, especially as fuel pressure issues seem to be a frequent occurrence. You should be able to monitor the fuel pressure in live OBD data.

If you have the 4.2, I believe that they all have a pressure regulator. This is fairly cheap and very easy to replace (10 minute job) so that might be a place to start as the fuel pump/s are a bigger/more expensive job.

Richard

[QUOTE=Biff Baxter;2870770]My 2007 Jaguar XKR has about 130k miles on it. For the last month or two it runs rough at times and then throws codes. The codes are not that consistent (fuel rail, cruise control, crankshaft, camshaft). I charge the battery overnight, clear the codes and then it runs fine for a while, sometimes weeks without throwing codes. The other day it was running rough and then stalled several times while I drove it home. It seems like the rough running is happening more frequently between charges although I am not 10% sure of that.

I read some articles here and saw the suggestions that there might be an electrical drain somewhere. When charged the battery shows 12.4 - 12.8 volts and when running the voltage is 14+. It starts every time without issue. It often starts running rough after I have driven it a few miles.

I brought it to the mechanic yesterday and today he said it was fine, no issues. He said an electrical drain would have to be large and would stop the car from starting at times. He tested the battery and the alternator and cleared the codes. He ran it and found no codes that indicated any electrical problem or other problem. I told him I was sure it was not fine, that it might take a day or 2 weeks to run rough but that it was happening consistently. He said he will run more tests. They do European cars but more German than English.

Any insights would be appreciated (other than get a new mechanic). I listed the dates and the codes I have seen below.

Biff - Get a CTEK 5.0 Battery Charger / Maintainer. It tests, refurbishes and maintains your battery. It’s the best $85 you’ll spend besides getting a Kingbolen SoloScan.

These cars are literally dozens of microcomputers connected by several networks and are designed to tell you what’s right and wrong with the car, but you have to provide clean, stabile power. Start with the battery.

Ground points....

There's lots of them

The codes are primarily fuel pressure focused.
I think you can ignore the cruise control code as its probably a spin off from the poor running condition.
Add to this your experience of poor running, I agree the fuel system should be looked at first.

These specific codes do not indicate a battery in poor state. Modules of lower priority are the first to “fail” with a poor battery. EPB, and the nav screen for instance.

When was the fuel filter changed? Or change it again, and open the existing one up.

Take it to a Jaguar specialist... The majority of mechanics haven't got a clue about these vehicles and will go around in circles just wasting each others time. It's not fine there's fuel pressure issues.. I replaced the fuel pressure sensor on mine as I broke off the nipple for the vacuum line by mistake.. it's fiddly but easy to do. It's possible the sensor is past it's usable life but it needs someone to diagnose what's happening.

Note that the FPR on the 4.2 fuel rail has a vacuum line to the throttle body (and other locations). This line is crap and will fail at a touch due to age. When it fails it will cause significant changes to LTFT and STFT (trims) as a vacuum leak. Look for the grey tube at the back of the throttle body, connecting to the FPR. You can remove the vacuum line connectors, leaving 5 mm or do of line, and replace the old crap with new rubber line by slipping the new line over the stub of the old one and using the old connectors and a bit of glue.

Thank you for all of the responses. The mechanic held the car for three days but it looks like he might be on the right path.

RichardS - The mechanic ordered a fuel pressure sensor and will be replacing it on Monday. I wish I had done that myself to save a chunk of money but the car was stalling and I needed a quick fix. I didn't expect the mechanic would have it for 3+ days.

panthera999 - You nailed it regarding a vacuum hose. One was disconnected and old so the mechanic replaced that.

In my original post I forgot to mention that there is sometimes a smell of gas.

I'll update this post after the sensor is replaced.

Thanks again for all of the replies.

Biff

Update: The mechanic replaced the fuel pressure sensor/regulator and a vacuum line and the car is running much smoother. On the downside, there is still an occasional smell of gas and I it is still throwing codes. For the last two days, it threw the following codes after some driving. I cleared them each day.

P0087 $07E8 Fuel Rail/System Pressure Too Low
P0193 $07E8 Fuel Rail Pressure Sensor A Circuit High

Biff

As I said previously, I think that the only way you will really get to the bottom of this is to measure the pressure in the fuel line whilst actually driving the car under different load conditions. This can be done with a suitable OBD reader or, with more difficulty, an analogue gauge.

Richard

Doesn't the supercharged model have dual fuel pressure/sensors? I thought one for each bank. If so the second one should be changed.

No it does not.

Follow what Richard has posted above. You need the actual fuel pressure. The test port (Schrader Valve) should be on the passenger side of the engine at the back of the fuel rail. Now we have seen that on the later 4.2L engines Jaguar dropped this test valve. Check if your car has one or not.
I thought replacing the FPR would fix this and it did improve the car but looks like you may have additional problems.

One guess is with the age and miles on the car consider your fuel pump might be marginal. They usually start failing slowly rather than just quitting altogether. But again we need fuel pressure numbers.
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