Hi all, I recently bought an 04 XK8 and the CEL came on immediately. Had the common PO171 and 174 codes. After much reading here, I changed the fuel filter and all was well for three days then the 171 came back. I bought a smoke tester and found what I think is the problem. At the rear of the engine, just below the throttle body on the rh side there is a nylon/plastic tube that enters the side of the intake to TB adaptor. The tube is 9mm diameter and goes to a grommet on the inner fender well and to parts unknown. I suspect it may be a vapor tube but don't know. There was obviously an o-ring and snap in connector there at one time based on the debris in the area and those parts would have sealed the tube and held it in place. But I can't find anything after hours of searching, that gives me a part number or name for those parts. I keep looking for a diagram of those parts to no avail. Can anyone help me identify those parts? Please!!!

 

That sounds like the vacuum connection for the power brakes to me. If on the right hand side

 

From previous discussion.

https://www.jaguarforums.com/forum/x...s15816-246341/

 

I'm lazy, smeared some RTV around the fitting to seal it.

 

Having now dug the remains of two of these connectors from their respective TBs while the vacuum connector right next to it remains apparently functionally unperturbed after 20 years, I wonder what design imperative led to this 'finger trap' solution rather than the 'push on' vacuum connector right next to it.

 

The engineers proably decided that why put a standard vacuum hose that can bought anywhere when we can design a part that is specific to our cars and we can sell for $100.

 

Exactly. And add labor to that for our unskilled or impatient owners and you've got a cash cow.

 

I thought seriously about doing that. It can't be seen easily so nobody would know.

 

Automakers aren't known for being efficient with design. That is why it is people job to go into a car design and simplify things down and make them more reliable. I guess Jaguar didn't hire someone to do that or they didn't do a very good job of it.

 

A quick follow up: Thanks to the excellent responses to my initial query, I received the correct parts yesterday and installed them this morning. I've driven the car all day with no return of the CEL. I couldn't make it to the end of the street before with it coming on so I am pretty sure it is fixed until the next issue pops up. Interestingly enough, the cruise now works and the "check lights" message is gone too. I know this has nothing to do with the prior problem but the test drive was more fun this way! now I'll check the proper threads for a posible explanation for this mystery. But I gotta say, I get more people oogling this car than any of my other cars, even my 62 Nova gasser and 64 Impala SS. Go figure! Thanks again for all the help! You guys are awesome!

 

Oops...I spoke too soon and too optimistically. Things were fine till I stopped for breakfast at a restaurant this morning and as soon as I restarted the car boom! CEL again, said restricted performance but that went off after a mile or so. Same freakin 171 code. I have a new MAF sensor, fuel pressure is up to over 50 psi after the new fuel filter, I fixed the vacuum leak at the brake booster tube and the smoke test didn't reveal any other exit points except out the rocker cover hole where the pcv tube connects (because the tube was off at the time. No other codes other than stored ones that I can see...I'm getting weary of this. Reader says it passes O2 tests unless I'm doing that wrong. I'm stumped.

 

Have you replaced the two VVT solenoid O-ring seals? They bake to a hard plastic crisp after just a few years in the engine bay and begin to allow oil and air seepage. The last P0171 / P0174 codes thrown by my wife's 2006 XK8 were caused by a baked set of these seals. In more than 9.5 years of vehicle ownership, I have replaced these two seals at least three times. The part number for the 4.2 engine is AJ82856 and they are available from several aftermarket sources for reasonable prices....

 

Jon89, no I have not replaced the vvt seals. Heck, until you asked, I didn't even know what they were. I've since read a few threads, watched a couple of videos and learned a bit. I checked my car and the one on the rh side seems soft when I poke it with my fingernail but the left side is hard as a brick bat. I don't see any oil around them though. I ordered a pair but still don't understand what they do that would cause a 171 code for lean bank one...?

 

Whether replacing the old VVT O-ring seals resolves your P0171 / P0174 issue or not, it is wise to do so. Old seals eventually leak oil and air. Good luck and keep us posted....

 

Well, hello again to all. After three attempts to get the right VVT seals I finally succeeded and installed those per Jon89's recommendation. You were right Jon89, those things were hard as a brick bat and both seeping oil and one had a sizeable crack in the lip. In the mean time I reviewed a few more threads on the 171 subject and realized that my oil dipstick was actually missing the "pilot" shoulder that holds the o ring and protrudes into the tube. Got a new dipstick off ebay and installed that too. Then while putting the oil fill cap back on I noticed the tube that goes into the rocker cover was loose. Pulled it out and someone had put an extra o ring on it for some reason and the ring was split and hanging out the side. I was able to determine that the original seal was ok and locked the tube on so tight that I darn near couldn't get it of again. I sealed it with a thin coat of black RTV and locked that puppy on the cover and checked the cap seal. It was good so it's all back together and no CEL today. I'm crossing my fingers...

 

Update: I've driven this baby a lot and under all types of conditions and no CEL has reared it's ugly head!! Thanks again to all of you guys! Wonder what'll break next...?

 

Good so far. I'd check fuel trims (especially at idle with a hot engine) so you know if you got all the leaks.

 

OK JagV8, I'm game to check the fuel trims but only one issue: I have no idea what they are, how to check them or what to do if they are out of whack. I have a decent reader that I'm just learning to use. Is there a thread in the forum that would be entitled "fuel trims for dummies"?

 

Dozens or hundreds by now. Search

 

To get you started, member XJRGUY wrote a paper that explains what they are: Also attached
https://www.jaguarforums.com/forum/g...17/#post304460

Also attached