PM on the way. Thanks Jules! You may be my new best friend. :-)

 

Thank you kindly. That is what I ended up doing, sort of. I went to Jaguar Heaven out of CA, they just sent the part, and hoping it is the correct one, since they discontinued making it, which makes no sense. Thanks again.

 

The P0171 is a lean code and because you do not have a P0174 code you problem is related to one side as you mentioned earlier. I would be looking at the fuel presentation on bank 1 meaning your injectors. I would suggest adding BG44K to a full tank and see what takes place. If that does not clear the problem I would look at replacing the O2 sensor. This is assuming that you do not have an exhaust leak on that side.

I had a problem on my 99 with my fuel trims (no codes) after replacing plugs, coil packs and the use of BG44K I then replaced my purge valve and it brought all my fuel trims in line.

 

Hi Gus. Good to hear from you. I'd agree with you, except both side FTs are high (12 on the left and around 19 on the right. They do come down a bit while driving (9 & 12 respectively). She's got all new O2 sensors and she'll get all new gaskets and seals in the process of installing new valley hoses. The plugs look good, so I don't think the injectors are a problem, but they'll get cleaned as well while they're out of the engine. All this and an intact EGR pipe ought to nail the FT / RP issue for another 190K miles. Nice.

 

Well, a blown valley hose (at 90K miles) advanced my top engine project. So every hose, every seal and every gasket was ordered and replaced over about two weeks of evenings. I must say, it was about time too. Almost every rubber seal had been reduced to hard plastic. In some cases I had to break them free in crumbling pieces. I replaced the brake booster tube seal with an ingenious 3/8 compression fitting. Thank you to whoever came up with that idea - brilliant! And, lo-and -behold, I found that my EGR pipe had a bellow cracked 3/4 of the way around. I'm pretty sure it was because of the Asbestos sheath that the propane test didn't find it.

So now my FTs, which were 12 & 19 and idle; 8 & 11 during cruise, are 3 & 7 both idle and cruise. No P0171; no CEL. Sweet. It could have been any combination of things, but the cracked EGR pipe was an obvious culprit.

For those of you chasing the P0171, check your EGR pipe. It's easy to get to and easy to replace if it's cracked and to tighten if it's just loosened.

 

You shouldn't really have anything over 5 on Short Term Fuel Trim. The fact that you don't have any other codes, and you've sprayed down everywhere you can think of, and no change in idle or fuel trim data makes me think it'll be in a sensor somewhere, most likely the MAF. Even though you cleaned it, doesn't mean its fixed the problem. Sometimes you can get away with it, and sometimes you cant. I've been down this road many times. Do you have a way to monitor what the MAF is doing say at idle speed, and when you rev it up in stages, in 500 rpm increments to see what the MAF is doing? I've had several using Datalogger on SDD where the MAF shows 7 grams per second of air coming in when the I'm driving the car at 60 mph down the road, when it should be higher. If you have a way of monitoring various sensors, that would be the way to go.

 

Hi JB,

You misunderstood my last. As far as I'm concerned, the problem is gone. Those were the Long Term Fuel Trim numbers I gave, which are now around 3 & 7 (left/right). Yes - my Short Term Fuel Trims hover right at Zero both for idle and cruise. She's always run very, very nicely, but the engine's additional smoothness since putting it all back together is pretty obvious. All is good!

I wish I could tell everyone that entire project was easy, but it wasn't - it took me about six or seven evenings of work. The Manual skips things that really should be in there, like removing the EGR from the back of the elbow so you can get the elbow out, and removing the MAP sensor from the elbow so you can get to one of the elbow to supercharger bolts. While I had everything out, I also replaced all the heater hoses - there is so little guidance on this in the manual, that I think Jaguar forgot about it altogether. Replacing them was another royal PITA. All that said, we pretty much have no choice but to do this project ourselves. All parts (hoses, gaskets and seals) cost me about 6 or 7 hundred dollars, and luckily our own JulesJag1 helped me out with the EGR pipe off his parts car. However, the labor cost to have someone else do the job could easily have been 2 to 3 thousand dollars.

 

Hi I've had the same code on my jaguar before with poor vehicle performance out of curiosity does it just go up to 90mph and stay at that speed, have you installed an new alternator on the car. sometimes it can be the comms wire confusing the system check this out

 

Hi Jagxk891. I'd like to share my experiences with you, but I do not understand your post. Could you add some clarity to it?


BTW: I still have the original alternator installed. I'm not sure what the "Comms Wire" is.

 

Hi Scardini1 I have had the same code and restricted performance on my jag and went all through it, the problem on mine was the communications wire not feeding back to the instrument cluster confusing the system once the comms wire was sorted out and feed back to the cluster all the error codes had cleared

 

OK. Understand about the comm wire now. Although that may not have been my problem, it's good info for others chasing various CEL codes. You said your car wasn't running well though. Did the comm wire effect that? In your first post you mentioned 90 MPH. Was that just a typo? My car has always been capable of 100+ with no effort.

 

The comm wire affected the performance a lot it would not go any faster than 90mph as the whole feed back to the cluster couldn't be read properly and the throttle was hyper sensitive

 

Wow. What a nightmare. That really is good info! Thanks.

 

@ Scardini...... to be honest, I haven't read all the posts in this thread, but I do understand what you are saying. I was just merely stating that if you're checking short term fuel trim, you really shouldn't have anything over 5%. The EGR pipes on these are prone to failure, be lucky you don't have the S-Type R or the XFR 4.2L, they can be a bit more tricky, plus in my opinion less room to work with. Also, if you ever have the same code come up again, and if you have flight data recorder logged, look at the information carefully, such as vehicle speed, rpm, coolant temp, etc, and compare to the g/sec of the MAF. I have seen on many occasions where the MAF isn't giving the right information to the ECM, and can cause the P0171 and P0174 to be logged. Just a bit more info for you guys.