Fuel System Problems:

A month or so ago, I had a low coolant light for a week. (refilled, it went away.) The day after, a PO172 code came in, Restricted Performance and Service Engine.

Took it to Jaguar Tulsa, they replaced MAF. 2 weeks later, PO172, PO175 codes are back. The dealer ran a battery of tests, including testing the fuel system and found no leaks or faults, and the new MAF was doing well. The code was cleared, and in the 3 weeks up till now, the car was fine.

Now, I have PO172 PO175 codes, and I remembered... the car has needed a fuel filter for 10000 miles. I had put that off. I have taken it to Firestone & Mobil 1 (oil change places) for a Fuel Filter, and Mobil sent me away after 30 minutes, saying they were afraid of breaking the line. They said it had rusted to the fuel line. At Firestone, they said they couldn't get it off without breaking the fuel line, and that they would look at it the next day, after penetrant had done its job. I drove the car to my apartment, and let it set overnight with the penetrant. Drove it back tonight, and they basically said it was almost certain to break if they put on the necessary torque. So, I drove 60 miles, basically, total, getting nothing done at all. I need to take it to a proper mechanic obviously, so I will ASAP.

But, for now, the car turns over an erratic amount of times, (between 2 and 8 times) between its starts (starts OK obviously), and the idle is becoming less and less stable (RPMs) with the coming of cold weather.

Is it possible the fuel filter is causing these fuel pressure problems?

Also, I just ticked over 50k, but I am short on cash. What else do I need to do to prevent problems in the next few months (winter, which is cold here)? I have thought of trans. fluid change, brake fluid, it doesn't need all that much I don't think. a 50k service would normally include quite a lot at once I guess.

Sorry to write a novel lol. Help is appreciated.

P.S. I think I will have the fuel line cut & spliced, to get out the old filter. The new brass bit would make it easier next time around too.

 

There is no indication in the DTC Summaries that a blocked fuel filter would produce a rich fuel situation indicated by P0172/P0175. A real rich condition could well produce the starting/idling issues you describe by fowling the plugs.

I would concentrate on resolving the above codes before worrying about the fuel filter. Continuing to run rich can get real expensive about the time you have to replace the CATS.

 

Hi
Here are 2 forum threads that have your P0172 and P0175 on at the same time (both mention using a fuel pressure tester):

https://www.jaguarforums.com/forum/xj-x308-xj8-xjr-27/xj8-p0172-0175-come-same-time-12721/
https://www.jaguarforums.com/forum/xj-x308-xj8-xjr-27/first-time-codes-17193/

Jim Lombardi

 

The car went through a battery of pressure tests at the Jaguar dealership, but no obvious faults.

Thanks guys, and I never considered the spark plugs were getting fouled up by the running rich, it runs ok as far as I can tell.