HELLO, MY FIRST CALL FOR HELP, 2002 XJR 142,000 MILES....FOR THE LAST TEN MONTHS I HAVE HAD THE MIL LITE COME ON SOMETIMES COUPLED WITH THE RESTRICTED PERFORMANCE LITE...iT'S BEEN DIAGNOSE AS (1) UP STREAM O2 SENSOR...REPLACED BOTH..(2) DOWN STREAM O2 SENSOR REPLACED ONE, (3) TEMP SENSOR REPLACED..REPLACE SPARK PLUGS, AIR FILTER...THE CODES LOGGED ARE ALWAYS PO175 RICH RUN AND PO 172 RICH RUN...NOW THE STRANGE THING I CAN CLEAR THE CODES AND DRIVE AS MUCH AS 3 TO 5 WEEKS 300 to 500 BEFORE IT RECODES...THERE IS NEVER ANY DRIVEABILITY ISSUES, DRIVES FINE IDLE IS A PERFECT 650rpm ????? ANY IDEA'S WOULD BE WELCOME THANKS FOR READING...CAPTMAL007

 

Welcome to the forum!

I do not see anything about replacing the MAFS which is third leg of the F/A stool. What kind of miles/gal are you getting?

 

This is pointing towards either the MAF sensor or a faulty connection at it's pins. Both cylinder banks are affected so it's unlikely to be the O2 sensors as these are individual to each bank-unless they have both failed at exactly the same time, which is unlikely although not impossible...

However, the MAF sensor is common to both cylinder banks as the fault codes P0172 & P0175 are for each bank of cylinders. A workshop with a Jag in for this fault traced it to bad conenctions on the MAF sensor-after cleaning the contacts the fault disappeared & the customer didn't bring the car back again.

 

I agree with the likely diagnosis, but the real way to figure it out, short of just replacing the MAF, is to monitor the LTFT and STFT signals. I will asume you do not have ready access to a scanner that charts parameters, so I suggest you read how to clean the MAF (it is easy to bugger it!) and give yours a good cleaning. For real cleaning, remove the element from the housing.

 

Hi Thanks for the reply....mpg avg 18.5 to 19.5.. upto 20+ on a freeway drive..

 

That's a little low compared to mine but not so much as to describe a hard MAFS issue but still remains a prime suspect.

 

I just had a recurring P0175 light with restricted performance as well would clear for a day then return, changed what seemed to be an extrememly plugged air filter from the previous owner and put some fuel injector cleaner in the car. Smogged today with flying colors after clearing code last night never had the P0172 just the one bank alone, dunno if it could be something so simple on yours or not. But you never know I replaced withs Mann filter as well.

 

IT SEEM GROUP OPINION IS THE MAS AIR FLOW METER/SENOR...ADDL. INFO I HAVE SERVICE HISTORY ON CAR IN AUG OF 2010 AT 120950 miles the car had the exact same Issue and a new AIR FLOW METER ASSY was Installed that was about 5K miles before I owned It...What you all think??(job was done by Jag dealer) Also I have been told the TPS and or the Throttle body can create same symtoms?? YOU THOUGHTS PLEASe CP777

 

Definitely don't listen to me, my check engine light came back on ill be making my own thread soon for my DTC. as I have only the single bank rich code not both.

 

Try cleaning MAFS.
Here is a DIY PDF file on detailed maintenance for Throttle Body, Mass-Air Flow Sensor (MAFS), and Part-Load Breather Tube orifice:

https://www.dropbox.com/s/tf92plcnjb...d.Breather.pdf

Jim Lombardi

 

Also take a good look at your air filter.

 

Hi, Thanks for your reply...What is LTFT and STFT ?? I just bought a cheap($100.00) scanner, still learning how to use It, tried my first live scan today and came up with bank 2 sft 0%...I have no clue what this means Thanks

 

You got that right....But I still have the problem .. The air filter is a stock jag unit, the filter is very clean, replaced about 5K miles ago..What Is K & N ??......Thanks

 

This is a link to the K&N web page K&N High Performance Air Filters, Air Intakes, & Oil Filters

 

You could have a problem with fuel delivery to the engine and that could cover several areas from injectors to the pressure regulator. I would recommend using BG44K fuel additive first and see if that helps. FYI it is recommended by and used by Jaguar if you are concerned.

 

To answer your question, STFT and LTFT refer to the short and long term fuel trims. For a better explanation than I could possibly give, google "OBDII LTFT" or similiar. These numbers are the basis for interpreting fuel system control on a modern engine.

 

Are you using an experienced Jaguar shop? That seems like an awful lot of parts to be throwing at a problem without resolution.

 

Thanks for the tip, I just addes a bottle of FI cleaner,not BG but a name brand product... so I'll just wait and see what happens..CM

 

Thats a great question, I was recomd by a friend to Continental Imports In Oakland CA. claim to be Jag specialists, bUT I'm fast becoming very disillusioned with, I have been to them 7 times, first time they diagnosed one down stream o2 sensor...the other six, pull codes and give the could be this or could be that, but do nothing, clear the code and lets see what happens..the problem here they are 70 miles away so 140 mile round trip, I have put on about 1000 miles and still no resolve...Last time in they came up with the TPS...but as you all know the TPS is part of the throttle body, a $2000.00 part plus labor , A little too rich for my blood, on a guess?? If anyone knows of a good Jag shop in the Bay Area PLEASE ADVISE...Thanks CM

 

I do not know if Continental knows anything about repairing X-308 Jaguars, but I do know there are inaccuracies in their web page concerning tensioners on the X-308, so I would tend to be skeptical.