My S-Type has been giving me the Restricted Performance message when the car is turned on. Once driven nonstop for at least one mile the restricted performance light goes away but the check engine light stays on until the car is restarted. The codes given by the machine are P0171 and P0174. I replaced the engine crankcase ventilation valve, MAF sensor, air filter, the hose that goes from the crankcase ventilation valve to throttle body, breather hose that goes to driver side valve cover, and both valve cover gaskets. The fuel pump was switched out a little over a year ago. Below are the rest of the readings given to me:

Reading at idle:
STFT B1: 12.5
LTFT B1: 19.5
STFT B2: 11.7
LTFT B2: 19.5
Fuel Pressure (psi 55.9)
MAP (inHg): 8.8
Eng RPM: 654
Spark Adv: 7
MAF (lb/min): 0.449
TPS (%) 3.5
O2S B1 S2 (V): 0.685
STFT B1 S2 %: 0
O2S B2 S2 (V): 0.105
STFT B2 S2 %: -0.7

Please help.

 

are these code you are getting is coming from jaguar dealership? dont trust non certified software diagnostics. i had this problem like forever and guess what.... the effing cat was bad. start there

 

have you checked for an air leak ?

 

LTFTs look very much like an air leak. What are they at 2500rpm (or near that)? In park will do, just rev for 30 secs so the readings settle a bit.

 

You have exactly what I had, you readings are identical. My problem was the brake booster pipe o ring in the Throttle body elbow. The bad news is that to permanently fix this its a new Elbow at $1100 not fitted or you could do what I did and get my Mechanic to use some silicone around the pipe, this still cost me $300 because of where it is. Result LTFT's below 3 and no engine light.

 

@kaiman the codes were given to me from a 3rd party Jaguar and Range Rover only mechanic. How was it determined that it was the cat?

@police666 I have checked for a leak but can't seem to find one.

@JagV8 When the car is reved to 2500 the STFT's go to -0.4 all the way to 2 and the LTFT's also drop.

@Robert Page Did you get the part number of the brake booster pipe o ring?

 

Ignore STFTs. Where do the LTFTs go then?

 

From 0 to 7 depending how long i hold it rev'd.

 

Weird. Should settle.

Looks like you have quite an air leak.

 

The next place I am going to look is the brake booster hose like Robert Page suggested. I just need to figure out how to take it off and the part number.

 

Robert;
Where is the O-ring? Is it on this power booster diagram?


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Club you are looking at the wrong end, see the pipe 13 it goes into the Throttle body Elbow which connects to the throttle body at the rear of the engine. You cannot see the connection without an inspection camera that is how inaccessible it is. The O ring at that end leaks causing the codes. The O ring is available the retention clip is not and this means to fix it completely you have to replace the elbow. The part is $1100 and fitting brings this bill to $2500! I had my dealer run a bead of silicone sealant round the connection and that fixed the codes and LT's but was a temporary fix. I was so pissed off with this 3 cent O ring causing this that I sold my XJR I had had enough. If you go to the XJ forum and search Throttle Body Elbow am I screwed you can get more info. Good luck to you.