Restricted Performance and Codes P0171 and P0174
 

Here's the story. A month ago today my fuel pump(s) failed and I had my car towed to the Jag dealer in Jackson, MS. They replaced the fuel pumps with new oem fuel pumps and I picked it up on Tuesday; everything was fine. Yesterday, I drove home to Denton, TX from Mississippi. Twice on the way home I got a restricted performance message and yellow/orange engine light but no other issues. The car drove normally at highway speeds and after about 10 minutes the restricted performance message cleared but the yellow/orange engine light remained lite. Today I had the codes read at AutoZone; they were as follows: P0171 and P0174 Faulty HO2S (heated oxygen sensor). The yellow/orange engine light is still on today but I have not had any restricted performance messages. Recommendations, suggestions, secret incantations, small animal sacrifices suggested?

Mark

Actually, those are the Codes for Bank A and Bank B Too Lean.

Usually a Leak in the Intake Duct or a Vacuum Leak.

I thought that was what those codes were for but the AutoZone print out said Faulty HO2S (heated oxygen sensor). I just had the fuel pumps replaced, could that have had an effect? Do I just need perhaps a few drive cycles? As I said, the car had no observable symptoms.

Mark

Had the identical issues. Would clear the code and you could drive all day with no problem. Shut her off and it would appear after restart, last 2 min then be gone but leave the light on. Master Jag tech said it was 99.99% the MAF sensor. Changed it ( takes 2mins) and code free since.

Always refer to the the Jaguar explanation for the codes, not the ones given to you by Autozone, etc. They are often very different.

As referenced in post #2 above, check the accordion-pleated section of your plastic intake duct. It breaks down over time and heat cycles, and the pleats wear out to expose big air gaps. I had to replace ours in October 2012 at just under 52,000 miles....

I had these codes also. Autozone said it was the MAF, bought some MAF spray cleaner, problem solved. I now spray clean it once a year.

The AutoZone guy wanted to sell me some MAF spray cleaner also. I said no because I wanted to check with forum before I did anything. I think I'm going to let is go for now and see if it continues. If it does, I'll investigate further.Mark

A big thanks!
 

Thanks to this post I

(A): didn't panic when the check engine light and restricted performance message came on in the 99 XK8 I just bought.

(B): got a code reader and read the codes (P0171, P0174, P1000)

(C): bought a new MAF sensor on an auction site for $40

(D): Replaced it in 2 minutes

AND most importantly.... I am now light free and code free!

My thanks to all of you!

RP still randomly appearing
 

Similar problem for two years. First, I have changed both up-stream, O2S (not a cheap repair). Rp still comes up. Sometimes after 5 minutes of driving, sometimes after 80 miles. Usually stays on for 30 seconds and display returns to a normal function with check engine light on. Always code P0174. I replaced MAF sensor - no change. I checked for vacuum leaks (spraying a carb cleaner around vacuum lines and TB- could not find one. Actually, i found that the hose from the valve cover on the LB is making a nose, when engine is running and virtually collapses. PCV valve is operational one way as it should. When I disconnected the hose and and plugged it, it created enough vacuum to collapse. Thus, I carry with me a cheap harbor Freight scanner and erase the codes regularly. I took it once, when the problem started, to an authorised service. For about $ 180 of diagnostics they did not find any problem. (It must have been that day when the car runs 100 miles without throwing RP message and P0174 code. Does anyone has any idea than to sell the car? It is 1999 model with 150 000 miles - so I do not want to spend more on repairs than is a residual value of the vehicle...

Thanks. Which auction site did you purchase the MAF sensor from? Thanks again.

Similar problem
 

In my case it turned out to be a bad evaporative purge solenoid which was hanging but not sticking enough to throw the P0443 (except once very quickly) and causing the lean codes when it wouldn't clear. Once it was replaced my lean codes stopped happening and the problem went away. Up till then we'd tried smoke tests and changing out every part of he intake and all 4 O2 sensors were new. The valve sits right behind the wheel well liner on the driver's side on my car. Maybe a 20 minute job to replace it (hardest part is bending the liner out of the way enough to get access to the damn thing.

Went fishin'
 

Ok, after reading all of your suggestions, I took a close look at all clips, hoses, etc, looking for leaks and loose parts.
1) found that there is a hole in the radiator hose, leaking coolant
2) found there is a large tear in a hose that leads to the throttle sensor, I took a photo:
Attachment 90114
I am not sure what this hose part is called, nor how to "patch" or replace. Any help is appreciated.

Thanks!

DJ, I can't tell what is leaking in that pic?

Apologies, the photo is for the hose leading to what i presume is the throttle section. The hose has a flash light aimed at it, so is lighter than the rest of the photo. It seems to be quite a large gash in it and when the car is running, if i place my hand over it, the hissing goes away, though i am unable to see if the engine light and RP message stops.I plan on going to the Autozone to see if they have the hose part or a patch material.

As for the radiator hose, while i cannot see the hole, i see leakage of coolant. Thank you, sincerely.