Friends...many of you have tried to help me with this persistent lean issue to no avail yet. The car is now a back up car since I purchased a low mileage xf as new daily driver. But I still gotta fix the s type to smog it. Most recent thing I did was tear it down and do the lower intake gaskets. So now I have done imt o rings, all intake gaskets, maf sensor, repaired cracked purge canister and leaky fuel tank seals, gas cap, fuel filter , air filter, all coils and plugs, smoke tested twice, and thoroughly examined and double checked all vacuum lines. Still get 0171 and 0174 as PENDING, not hard codes and the cel comes on. When reading with my torque app obd tool, I notice that the o2 sensors #1 #2 both sit dormant until car is fully warmed. During this cold idle period is when the fuel trims run really high. And trips the cel and restricted performance comes on. Then o2 bank 1 sensor goes to .9v and as soon as does, the bank 1 fuel trims start to go down. Eventually the o2 bank 2 goes to .9v and when it does then bank 2 fuel trims drop. When both banks stft go to 0 or slightly negative, the ltfts begin to drop even at idle with no throttle. When all the fuel trims drop close to 0, the restricted performance turns off, but the PENDING 0171 and 0174 remain as does the cel. Readiness monitors Evap and o2 sensors refuse to complete. Would it be possible that faulty o2 sensors are causing all this grief? 2005 s type 3.0 200,000 miles

 

I've wondered the same thing. The late model O2 sensors aren't cheap, but I think it's a reasonable stab. They are normal wear and tear items, after all.

Remember, there is no "lean" sensor. The fault is triggered by a set of inputs the computer interprets as a lean condition. So much of the engine control is based on the O2 sensors, and we mortals have no real way to know if their calibration is still accurate. Meanwhile, the computer still keeps adjusting the fuel to make the O2 sensors happy. Unless grossly inaccurate, the computer has no real way to know if the sensors are still within specs.

So given the chance to spend your time and money, I'd say go for it. Make sure you get a name brand with the correct connector. Stay away from the bargain brands that require splicing the wires.

 

Just a thought, I'm sure you have check this already, but how is the breather tube off the ccv doghouse under the intake? I had same codes, basically same characteristics and Ltft of around 40%, and after changing some orings on the intake, tore into the intake plenum further I found upper and lower gaskets were shot, and the breather tube under the lower intake plenum in the valley to be cracked on the underside. Looked fine on first inspection, but after pulling it, it was definitely cracked. Replaced that and the o rings on the ccv doghouse and fuel trim backed down to around 3-4%.

 

The later 3.0 litre engines do not have the rubber breather hose under the lower inlet manifold.

 

Forgive me for asking a question that may have been already answered in one of the other threads.

If the MIL is on and the DTCs P0171 and P0174 are still present, what is the fuel pressure?

 

Thanks for looking at this nbcat.....according to the torque app tool, my fuel pressure is pretty much constant at 55 psi. I used the same tool on my recently acquired xf, and the fuel pressure is actually a little lower on that car than it is on the s type.
Let me ask you all a question on O2 sensors.....I'm a bit confused because I just read an article on jagbits parts site that says v6 motors only have one O2 sensor and the v12's have 2. That puzzles me because I have seen parts sites selling sets of 4 O2 sensors for this model. How many am I looking for and where are they located on the car? I appreciate you guys helping me.

 

The Jagbits article refers to the XJ6 inline 4.2 6 cylinder engine not your 3.0 S-type it indeed has 4, 2 upper and 2 lower we sell them all Jagbits.com

 

Next step: Have you confirmed this with a mechanical gauge? I can't remember if this has been discussed in any of the threads about your car.

I don't think that sensor is just indication. The fuel pressure sensor sends feedback that controls the pump output to maintain the requested pressure, right? If so, an inaccurate sensor could really mess up the pump output. The control circuit is fat, dumb, and happy, getting feedback that the pump output is 55 psi, or whatever the number is supposed to be.

Meanwhile, the real output could be who knows what, based on the faulty sensor, which affects the volume of fuel delivered, and it snowballs from there. This all fits into my theory about how computers are really, really smart and really, really stupid, all at the same time. So in a nutshell, please verify with a mechanical gauge what the actual fuel pressure is.

 

I strongly beg to differ as my 2001 3.0 definitely has it. The broken piece on mine was a small 5/8 90deg hose in the valley.

https://www.jaguarforums.com/forum/s-type-s-type-r-supercharged-v8-x200-15/does-2000-s-type-3-0-v6-have-pcv-valve-64103/

 

Your 2001 has it below the lower inlet manifold. The OP has a 2005 3.0 litre; the later 'facelift' cars do not have the breather hose. Please see his first post for the vehicle information.

 

I am concurring here.....there is no breather fitting under the intake manifold. And nbcat....i will heed your advice to get a fuel pressure mechanical reading, probably from a trusted indy here that did my fuel tank seals.
What should the psi be? Also for the heck of it, important or not, both banks do not simultaneously go lean. It is ALWAYS bank 2 first, and if left alone and not cleared, bank 1 eventually follows.

 

The fuel pressure regulator located on the fuel rail can also be failing causing momentary lean conditions to exist that may set the DTC.

The schraeder valve has been deleted from the fuel rail on the later engines, so an adapter must be fitted to provide for a mechanical gauge.

Fuel pressure should be between 3 and 5 bar.

 

Im thinking that installing some sort of adapter fitting on to fuel line is going to be beyond my confidence level. Where would it tee into? This engine just has the springlock fitting in the front that feeds the fuel rail. I hesitate to mention this, but since all I care about is passing smog, if the cel was somehow defeated or cleared while only having "pending" lean codes and IF the O2 sensor readiness monitor would magically complete.....tis car would pass california smog. You are allowed to have an incomplete evap monitor in california as long as no hard fault codes are present and no cel. What I don't understand just a little..is why is the cel coming on if no hard fault codes are popping up? Why are "pending" lean codes tripping the cel?

 

PENDING codes do not put the MIL (aka CEL) on.

Only actual codes do that. What are the actual codes?

 

jagv8.....that is what has puzzled me...there are NO actual hard codes ! In the past I have seen lean codes turn from "yellow" pending on my torque app to "red" hard fault codes. But for the longest time now, NO hard "red" codes appear......only "yellow" 0171 and 0174 stipulated on the tool as "PENDING". NOTHING ELSE. so I don't understand why the cel (mil) is coming on.

 

If the MIL is on (& it self tests OK) then apparently your tool is just not telling you the actual code(s) so change to one that works.

 

I am thankful for the help and not trying to be arrogant, but what do you mean "self-tests ok?".....I have another obd tool and it also only indicates 0171 and 0174 as pending., with no other codes other than p1000 which tells me the readiness monitors are not completing, and those two incomplete are evap and O2. I might take the car down to my local indy and see if he can read the obd with his tool and see what he sees.

 

The MIL (and other lights) should self-test at ignition on (they go on & off).

With the MIL on you can be almost 100% sure your tool simply is not telling you one or more codes. Sadly there are quite a few bad tools.

 

could you recommend the scan tool or mobile app that works best in these cars from your experience?
thanks.

 

Best: IDS/SDD.

Cheapest that appears not to lie (but only does the PCM as most tools only do): elm327. (But note - if you use it - that the Torque app has the odd bug e.g. with ECT.)