Check all the hoses between the throttle body and the cylinder heads. Most are with the norma connector that pulls off with a pinch between 2 fingers. Also, the PCV valve pops right off. Check the dip stick. All those have o-rings.

 

Yep, that's next. Doesn't look like the gas cap had any effect., shucks...

 

If your fuel trims are low at idle and high when under load, it could be (one of your) fuel pumps going. See what the trims look like in real time.

 

OK, fmertz/JagV8/anyone, I performed a low tech smoke test with cigar, hose, surgical glove connected to MAF assembly just aft of MAF sensor. It was ugly and reminded me why I don't smoke cigars, but it worked (kinda). Got small smoke trails from around base of throttle body below EGR(?). Also smoke in crankcase, if that's significant. But smoke was very light / diffuse and it was impossible to see exactly what connection(s) was culprit. Its a rat nest of vacuum hoses down there and of course they all lie below a big AC hose. Attached is a couple of pics of area. Any ideas?

 

Main question first: What kind of cigar?

That trail of smoke is part of your problem. There should not be a free path from the intake to the engine bay. You need to track this down. Somewhere down there below/behind the throttle body near the firewall, there is a piece of reflective protective cover over the EGR pipe. The bellows on that pipe are known to crack. You might have to remove the plastic intake pipe to get some clearance (and take advantage to inspect it, too). This EGR pipe connects the passenger side exhaust manifold to the throttle body.

Best of luck, keep us posted.

 

Hey, jmertz//JagV8/anyone, I did a smoke test with a DIY unit connected to MAF assembly aft of sensor and it worked (kinda). Got trails coming from base of throttle body below EGR(?) Also, smoke in crankcase, but dunno if that's significant. But smoke was so light and diffuse I couldn't see exactly which connection(s) were leaking. There's a bunch of vacuum lines down there and of course they're covered by a big AC hose. I'll try to attach a pic of area. Any suggestions?

 

sorry for repeat

 

Thanks to all (esp. jmertz, JagV8, JimmyL) but my hope of an easy-to-get-to fix has evaporated. I've had some DIY successes on my always-wanted-an-XKE-since-I-was-16, but this ain't gonna be one of them. It's my driver and I gotta get it fixed. Will let you know what the Jag shop finds out.
BTW, I think it was a Dutch Masters Palma.

 

OK, final outcome from P0171 code circus with supposed vacuum leak. Jag dealer diagnosed problem as MAF sensor problem (even after I went to trouble to clean it) ... not a vacuum leak. Replaced sensor. Tech said whiffs of smoke test from under throttle body were 'normal' (never heard that before on Forum). Dealer also completed a recall OBD II Deficiency upload. So, engine light is gone and runs great (always did). We'll see if it stays off.