Hello all,
I will start by saying I am somewhat new to forums and also new to being a “car guy” so go easy on me! This is a pretty lengthy story of a problem because I think I might have screwed something up at some point and idk when.
I purchased a 2003 Jaguar S-Type R(v8) with 145k miles and for the most part it drove fine. When I got it, the engine light was on and it had some error codes for misfiring cylinders(6 codes in all). It still drove fine except for if I tried to push it too hard, like passing someone on the highway. Then the dash would read “restricted performance” and the power would suffer. Also, it would take a good 10-15 seconds of turning over before starting. All other driving was fine. One day I decided to swap out all the spark plugs and ignition coils. The codes said that 4 or 5 cyclinders were misfiring and I always wanted to teach myself how to do it anyway. So I replaced ALL of the plugs and coils. I wiped the codes and drove a little bit but the engine light came back on. This time with less codes. I consider that a win. There was one code for a “random misfire” and then two codes. One for cylinder 6 and cylinder 7. Unfortunately, the condition remained the same. It would still enter “restricted performance” if I pushed it too hard at higher speeds. I was getting pretty tired of the excessive ignition time though so I thought I’d try solving that next. I had heard that it could be a problem with fuel pressure and one of the cheaper fuel things to do is get a new fuel filter. That takes us to today. I was able to swap out the old fuel filter, which looked to be original to the car. When I went to drive the car it STARTED with the “restricted performance” message on the dash. Just idling. When I put it in gear it struggles to go past 30mph. I have found that if I press the gas pedal hard it will max out revs at 1500rpm. There is a sweet spot though that I can barely press the gas pedal and it will build revs normally. I was curious about any new codes so I plugged in my code reader and to my astonishment ALL of the codes about misfiring cylinders were gone. Currently there are now only 2 codes. P0191(Fuel Rail Pressure Sensor Circuit Range/Performance Bank 1) and P1338(Fuel Pump drive circuit low/high voltage).
Is this because I changed the fuel filter? Now the car is practically undriveable. Should I put the old fuel filter back on? What happened to the misfire codes? I am so bumfuzzled about what to do.
TLDR: 2003 Jag S-Type R starts with “restricted performance” on and struggles to get up to 30mph. Codes are P0191 and P1338. Occurred immediately after replacing fuel filter.
Thanks for reading.