Let me give a brief history on my friend's car that we work on. He has a 2000xkr (95K)


About 1 year ago he was having the wonderful and constant 0171 and 0174- going to +25 on both sides. We tried a few things and then he just put it in the garage for 7 months and when he reran it (got a new battery at that point) he could never get the error to return, when previously it would easily appear. I am not a scientist of any sort, but never heard of a car fixing a vacuum leak by sitting unused in a garage.

Be that as it may, we have taken the car out and could never ever get it to have anything but an incomplete on the evap or ccm modules. Ran every drive cycle tha we have seen listed, including the TSB one for my S-type- as a last resort.

Finally pulled a 0455 code and changed the purge valve. No return of code or gas smells or anything of that type.

The fuel trims (LT) are showing at idle in the +1.8 and +.8 and at 2500 rpm +14.9 and +13,.6 ( somewhat high in my opinion).


The strange part of the fuel trims are when driving. I do not care if we are cruising at 20, 30, 40, 50, 60, or any speed and the fuel trims (LT) are at +15.5 and +14.8. I find it hard to believe that at holding a steady speed on a straight road that the ecu would see a condition that would need an additional amount of fuel to that point. (we have a clean maf and new air filter)

The second and more strange fuel trims I see and these are short term and before someone tells me that short terms are only good for diagnosing leaks (which I know) with an ether or other type product- these are quite bizarre and only discovered by accident.

If the car is at full temp and I am sitting at a stop light and go as slow as I can make the car move with my foot on the pedal- the st fuel trims immediately run to +25 on both sides. If I am doing 25 miles an hour and the LT are at the above mentioned level (+15.5 and +14.8) ST shows a variety of minus numbers and then step on the gas to go to 35 mph at a very light acceleration the ST go immediately to +25. Further if I am cruising at 60 and then go to WOT with the supercharger engaged the st fuel trims in an "OPEN" status go to +25 and my experience is that when in WOT the st fuel trims go to 0.

So I took out a friend's 02 xjr with the same engine and went through all the same tests and the ST never went beyond about a +7 or 8 when under slight acceleration and went to 0 when WOT was engaged. Even under heavier acceleration, but not WOT, it still never went beyond a +7 or 8 on ST

Albeit a different car, I tried the same on my s-type 3.0 (05 model) and the same experience happened that happened on the XJR

So what gives? I have to think a sensor is giving us trouble (probably an 02) and has yet to code. I do notice the graphing on the 02 sensors on my car are in a a very staggered pattered as normally seen and the 02 on the XKR tending to be much wider and more in loops. (also different than the XJR I tried- which was like mine).

Any ideas that might give us a direction. Could always be a vacuum leak when under heavier load- but going from 0-10 miles and hour or 25-35 miles an hour at a very slow pace is not putting the car under heavy load.

As as a second problem, there appears a loud clicking sound (not in a pattern) coming from somewhere in the center of the engine (not the purge valve- which is easy to recognize) and is most noticeable when the car is just turned off and for about 15 minutes- also heard at times when the engine is warming up at idle.- although it would be hard to hear while driving). Has anyone experienced this and what could that be?

Thanks for your patience in reading this and your help and thoughts.

Tom in Dallas/Plano

 

See if this helps:

03-xkr-bunch-codes-all-once-idling-like-crap-169298/

Best of luck, keep us posted.

 

Thanks and the good luck accepted.

I keep suspecting something below the Throttle Body, but now - not having the 0171 or 0174- I am not sure. Your seems t be somewhat similar in that you have misreads all over the place. I keep wondering is the loopy and long wave type graphing of the 02 sensors are a precursor to slow responding ones? Anyone has any thoughts on that?

Should add that the car idles quite smoothly.

Thanks

Tom in Dallas/Plano

 

Have you noted the fuel pressure during your runs? Low pressure could explain the high fuel trims at higher load.

 

Seems fine as I remember, but I will check today and see if it still is

Thanks

Tom