City driving is at lower speeds, and at lower speeds you will drive with more vacuum, so any small leak somewhere in the intake system will have a bigger effect.

If you have an ABDO reader, you should check your LTFT & STFT values, as when these reach a specific value (i think over 20% or so), it will through the lean codes.

The ECU will base the lean LTFT on the (measured) air coming in and the O2 sensor. If the mixture is lean it will increase the LTFT/STFT up to a certain percentage before it throws a code.

So, it is important to know that the MAF is working fine and the O2 sensors. Best would be to have the car checked externally of the lambda values (when it is in closed loop). If this is indeed the case, then you have ensured that the O2 system works fine. If not you will know it is the O2system (I say system, as it could be the sensors or even the ECU).

It seldom happens that the O2 sensors fail at both banks at the same time, so I would rule it out, but better to check and be sure, it is cheap to check.

If the MAF is ok (swap it with another one), then all that is left is either a vacuum leak, or low fuel pressure (for whatever reason). Fuel pressure can be measured, which is cheap to do. It could also be that some injectors are clogged, this is something you could find out now by cleaning the injectors (companies that do this also provide new o-rings!), or to check the sparkplugs.

Last most likely would be a vacuum leak, and if all other parts are ok, this is something you should be able to find as the leak isn't small if you are going able the 20% fuel adjustment.

The Xj8 also has air assisted injectors, maybe that pipe/(or solinoid on the TB) is leaking?

Hope this helps.

 

Read my posts. I guarrantee you if you follow the advice given me, you will love your car again. I am getting about 25 MPG and driving from NH to Long Island, NY and Vermont every week. My car runs like a new Jag. Do what I did even if you think it is not the problem. Cleaning the MAFS with CRC MAFS cleaner, getting into the throttle body with a lint free rag and the pedal held down with something, getting your fingers in that throttle body as deep as you can, clean the part load breathe with the 3/32" drill bit by hand. Vacuum leaks? When in doubt rip it out. Those accordian tubes suck. I used a comparable sized gasline tube with the old fittings and clamps. Make sure the O-rings and where they are fitted to are cleaned and have a "snap to" fit. That throttle body one with the T-connector is tough but patience will get it done. My car is clear of all codes, thank God!!! I was ready to give up, I didn't. I took the advice of forum members and prevailed. I would have probably spent more fixing things that did not need fixing at the dealer than I paid for the car. Also, fixing the car yourself gives you a sense of empowerment. We no longer have to lay back and take it. Spend your hard earned cash on other things. I spent less than $30 fixing my car. I still run Lucas Upper Cylinder Lubricant in every tank as a reward to my beautiful car. Good luck.

 

This is good information!

 

AWESOME!!!!! My baby is purring. Many trips from NH to NY and back without a problem. No codes, no CEL, no restricted performance. Only compliments on what a nice car I have. Not bad for the price I paid. I just detailed the heck out of her and now it is time to do an oil change.

 

I'am about to give up. I have only codes 0171 & 0174. I have read so much and cleaned everything per Gus' instructions. Purchased a kit with mirrors and followed every vacum hose looking for leaks and can find nothing. I changed the rubber gasket around the throttle body, fuel filter, ran two runs of injector cleaner & new air filter. I have never had any issue with this car before and really enjoy tinkering with it.

The CEL came on one day when it was raining really bad and then shut off the day after the rain let up. CEL remained off.
2 weeks ago it came back on in rain and never shut off. Also every morning on my way to work when I get on the interstate and hit 70 mph the Restricted performance lights for about 10 seconds and shuts off not to be seen until the next morning. In this time I have done all the things listed above.
Yesterday I go out in the garage start her up for our ride to work and out of nowhere the CEL is off car runs perfect to work no RP nothing. I decide to take it several places through the day and everything remained perfect. Then this morning I am about ten minutes from home and the CEL turns back on and RP for 10 seconds at the same place same speed. I really think this car is punking me. I keep looking for the hidden cameras. I have one week to fix this now because I have to take it on a trip and will be forced to go to the dealer which is not convenient at all and expensive.

I hope the Jag masters of this forum can give me something else to check and do. I just got my JTIS disk today and will play with that when I get home. Thanks in advance for anything!!

Also it is a 2001 XJ8 with around 90K

 

Hmmm, moisture getting to throttle body or plug somehow sounds like??. After engine heats up, moisture dries up...but just enough to cause your CEL.

 

I was thinking the same thing!

Go to this link and see if the plugs have been replaced. http://www.gusglikas.com/AutoRepTB.htm Also check your PM!

 

After a couple months and hours under the hood hunting a Vacum leak, it appears that I did not clean the MAF as good as I thought uning Gus's directions. I ended up taking my Jag to my local repair guy. After two somke test on different days they came back with no vac leak. They tested the MAF and said it was coming back bad. They basically told me they would try cleaning but I would most likely need a new one. He called a day later and said they felt he cleaning worked. They had driven the car about 45 miles with no codes/CEL. I have renewed faith in this mechanic because they could have easily got me for a new MAF and they did not. I walked out of his shop for 187.00.
Thanks to all who gave me input. Everything I was told was spot on! Thanks

 

tjcpt1, can you summarize all that you did, and what you believe was your cause for the leak?

 

Hi everyone, I am also a victim who suffer from the infamous p0171, p0174, and p1111. I neglected this problem too long and I am now paying for it.

I have a 2000 xj8 with 75000 miles. The CEL and RPL came on about almost 2 years ago. I took it to a dealer and they said it was MAF issue. So I had it clean by the dealer and the problem went away for 1 Month or so. I did not think much about the problem and kept driving it like that with CEL and RPL. About 6 months ago I clean the MAF again myself and this time the problem only went away for a week or so.

Most importantly, about 6 months ago I noticed my car stared to use oil. It has no leak but it is burning about 1 qt every 2-3 weeks. You cant smell it or see it in the exhaust, but you can kind of smell it when the engine has been running for a while. I am guessing it is because I have neglected the running too lean problem way too long. I went to autozone today and got a code reading of p0171, p0174, p1111. I wish I would have done something about it sooner, but now my JAG burns oil! Don't be like me, fix this problem early.

I am going to try my best by following this thread to fix it, but it seems like it has no been easy for many of you. I guess the only thing now I can do to slow down the oil buring is switch to regular oil instead of synthetic.

Any extra commit that you can offer to help is great.

Side-note-- I have been using Castrol edge 5w30 with Wix (napa gold) filter. Do u guys put 7 or 8 qts? the owners manual has a amendment page flowing around saying because there is a modification to the oil pan or something so the amount has changed. Also do you change it every 10,000 miles?

I live two hours away from a Jaguar Deanship so I pretty much is on my own on this one.

Thanks for reading

Johnny

 

Think about this you have a 2000 xj8 that has 75,000mi on it and you are using 5w30w in it. This is not a new car and it might be to your advantage to up the oil to maybe 10w - 30w/40w. Oil viscosity is mentioned in the owners manual with the temperature rating for proper use or you can go to this link that might give you what you need. http://www.bobistheoilguy.com/cms I see that your car is a 2000, do you know if the engine block is a Nikasil? If it is you may want to install Restore and see what takes place.

I am concerned with the burning of oil and the causes are many. You should look it over really good to make sure something is not broken. You say the car runs good and that is often a good sign.

As for the Restricted Performance Welcome to the crowd. You should check along with the MAFS for leaks in the vacuum system and check the breather stub http://www.gusglikas.com/AutoRepairPlugReplacement.htm You should also check that the air filter box is closed and seated properly. It seems that has been a problem in the past. I also have a procedure that might help http://www.gusglikas.com/images/Auto...otos/P0171.pdf I hope this helps!

The P1111 means that your on-board diagnostic test have been completed. This might help http://www.gusglikas.com/images/Auto...J27%201999.pdf

Also I will be moving this post on its own for others to contribute to.

 

Hi Gus, Your oil type comment made me feel a bit better. I thought I messed up my car by not fixing the p0171 and p0174. Although, what do you mean by installing a restore? and How do you find out about the Nikasil block information? And What does it mean if it is or not Nikasil?

I live in Missouri, today it is 0 degrees and in the Summer it gets to 100! What type of oil do you reconmand? 5w40??? stick with the castrol edge?? 7.5qt?

I printed out all the link you posted already. Thanks anyway though, I am going to try to get out of this RPL crowd.

Thanks man,

 

"Restore" is an engine oil additive, comes in a bottle. Look for it at your local car parts place.

 

And if your car was made before late summer of 2000, it has a Nikasil engine. This was a method of treating the walls of the cylinders. Unfortunately, under certain circumstances the wall treatment would wear away, and the remaining aluminum would be severely eroded by piston ring wear, resulting in increased oil consumption. Remedy is generally a new/different engine, sorry to say. Big bucks.

 

Yeah I seen that stuff, is it safe to put that in your engine? Is there one brand that is better? I always thought that stuff is useless or may damage your engine.

 

"Restore" is a particular brand of "engine goo." In this case, there seems to be some actual science behind the particular claims. There is a kind of suspended metal which tends to fill in somewhat the micro-pits in the cylinder walls, improving the sealing capability of the rings. Most of the usual engine goo compounds just thicken the oil. I haven't tried "Restore" yet in my Jag, but I plan to put some in my high mileage Buick Roadmaster, soon as it warms up.

 

I would have doubts about Restore helping a worn Nikasil engine. However, the stuff is only a few bucks a bottle. Compared to the cost of a new engine, it is trivial to give it a try.

 

I am like you Goo is not appealing but this comes highly recommended and I used it in my rav4 and at 266000mi it does work.
As for the oil you should look in your manual or go to that web page I gave you. If I were to recommend without knowing your car and with “0” temp today if 5-30 is not working I would go to 10-30 for now, the summer it might change.

 

I also have all the same symptoms with our Jag. we have tried many things that Gus has shared and to no avail. I did find a tee at the back of the TB a small one with tape over one end of it just sucking air like crazy. Fixed it the best I could and all is still the same. One thing though all the pictures of the MAF's I have seen on here are not anything like mine. wondering if somebody didnt put the wrong one in...hmmmm. Also is there suppose to be some sort of gasket on the plastic piece that goes over the TB(air intake hose)?

 

Go to your local Jag dealership with the MAFS and see what they say. As for the leak at the “T” fitting on the back of the TB if it is still sucking air it needs repair. You asked about a gasket on the intake tube it does have a gasket and if it is missing then the reading by your MAFS would be incorrect. If you have the car running and you use a can of TB cleaner and spray that area and the car stumbles you have a leak.