I have a friend that has a 2000 XKR (about 90k) and has been having trouble with p-0171 and 0174 and RP. Clearly the freeze frame show the ST fuel trims at about 21 on both sides when the rp occurs. He is under the impression is may have to do with the seal/gasket on the breather to the throttle bottle, although he has a new one that shows no problems unless it was made improperly at the factory (he got from Jag ***********). Any thoughts on that would be appreciated.

However he has gotten wild fluctuations in the short term ones when driving and running a recorded scan that would range in one frame at a +22 and then run to a minus 18 in the next frame on ST FT.

Yesterday, his battery appeared to be below normal- has has a Bosch- same as I do and newer and unless there is some well known power drain on the engine, then that is a touch strange.

What I found interesting is that when the codes were cleared and the engine off, but key on and when I took a data read is showed bank one o2 sensor at a negative -66.7 Ma. The car is not running. That to me was strange and I went to my Jag immediately and ran the same type of scan and got the bank one 02 sensor at 0.00- which seems proper. What would a negative read on an 02 sensors when the engine is not running mean?( to me it is a short and I would have zero interest in swapping one side to another- I would just buy new ones on a 15 year old car). Would an 02 sensor that has gone bad cause that much fluctuation in the fuel trims and never show a code for the 02 sensor after it gets to RP or is he clearing the codes too soon and eventually it would show, albeit the would have to run in RP to perhaps get it????

Has anyone on a 2000 XKR had a problem with a new gasket on the breather hose to the throttle body that cause a huge vacuum leak, assuming it was and had been put on correctly???

Could this also be a MAF problem although the data frames when running show the MAF is operating correctly and has been cleaned numerous times?

He was told that on a smoke test that there was an apparent leak near the throttle body ( could be the gasket), but could it be in another area of the the throttle body or below it or from the throttle body itself?

Thanks for your help

Tom in Dallas

 

You opened a lot of doors here! It's clearly lean. My guess is that you have a MAF that is not giving you enough fuel. You said the data appeared normal. What was it? Under full load at high rpm (like just before the shift), I would expect the MAF to read over 200g/s. If it is below that, I would try a new MAF. (Maybe an understanding fellow Jag owner will let you use theirs to try it first. Easy to swap out.

 

Check the accordion bellows of the intake pipe for cracks on the underside.

 

Thanks- actually the bellows and the whole assembly is fairly new. So we can't get to that simple. Typical. Any other ideas?

Tom in D

 

As Chopr said, try looking at the reported flow rate in different situations and see if the look odd. Have you tried cleaning the MAF?

If you suspect a leak, you can try the trick of spraying MAF cleaner on the various joints while watching the fuel trims. Crude but effective.

 

There have been a few instances of the bolts holding the EGR valve becoming loose, allowing air into the intake manifold.
Unfortunately, it is almost impossible to check them without removing the throttle body, but you may be able to introduce propane from a unlit torch under the throttle body and see a difference in the fuel trims.

 

That will be tried.

Thanks

Tom in D.

 

Thanks, but I consider cleaning the MAF as a standard maintenance item and I do it on my Jag and his once a month. Maf cleaner is just as good as other things to see if the data will change.

Thanks

Tom

T

 

What I found interesting is that when the codes were cleared and the engine off, but key on and when I took a data read is showed bank one o2 sensor at a negative -66.7 Ma. The car is not running. That to me was strange and I went to my Jag immediately and ran the same type of scan and got the bank one 02 sensor at 0.00- which seems proper. What would a negative read on an 02 sensors when the engine is not running mean?( to me it is a short and I would have zero interest in swapping one side to another- I would just buy new ones on a 15 year old car). Would an 02 sensor that has gone bad cause that much fluctuation in the fuel trims and never show a code for the 02 sensor after it gets to RP or is he clearing the codes too soon and eventually it would show, albeit the would have to run in RP to perhaps get it????

Tom in D

 

When looking at the fuel trims you should be looking at the LTFT not the STFT the STFT change so drastically and quickly based on your response and the engine reaction it is the LTFT you want to look at.

As for your P0171 & P0174 it could be caused by a misfire, air intake leak, fuel system blockage, fuel pressure, o2 wiring problem, exhaust leak and MAFS among other things.

My first step would be looking for an intake leak to do this I would use throttle body cleaner and spray around the vacuum lines “they are the known to crack and fail then work my way around the engine bay. The attached procedure should help.

Link http://www.jagrepair.com/images/Auto...otos/P0171.pdf

I would also be cleaning the MAFS and Throttle Body. I also have a chart for testing your MAFS but would hold off on that until you check for leaks. Do you know when the fuel filter has been changed? You might think about replacing it.

 

The LT fuel trims are up around 11 on both sides at the time of the confirmed fault with ST at 21.I appreciate your suggestions, but all of this has already been tried and done- with the exception of changing or checking the wiring on the 02 sensor. No misfires, fuel blockage or pressure problems.

My friend keeps clearing the codes after rp and I understand to some degree, but it needs to run and see what other codes develop. Resetting the battery is not going to solve the problem as the ecm cannot learn itself around vacuum leaks.

My big issue was seeing with KOEO data read that bank 1 02 sensor has a -66Ma reading. That is strange and suggests a problem there.

T in D

 

You are a victim of the egr bolt mayhem !

The two EGR bolts to throttle body have come loose, they may have even fell out ! Remove the throttle body,fix the situation,smear a little black rtv on the throttle body gasket, reinstall

Use a little blue thread sealer on the two egr bolts please

 

Thanks. That is the one thing we have not done. Will let you know.

T in D

 

I am going to give you a little reading material related to Fuel Trims it should help with understanding what is taking place.

Link JagRepair.com - Jaguar Repair Information Resource

 

Thanks I had read this some time ago and found it a simple way to understand how they work compared to the old carburetor and distributor cap issue.

I got my friends, whose car it is to read and he comes from the old days and this was a great piece of education for him.

I just still do not know why his bank 1 02 sensor reads a negative -66Ma with the key on and the engine off. However never once has he thrown an 02 sensor code. I actually read your experience in chasing down the leak in an XK8 and think he will find the same in his car as well.

Thanks again

T in D

Tom in D

 

Check you PM

 

I doubt it's meaningful to use OBD to read an O2 sensor except when engine on, and may even need closed loop.