My wife's 2011 XF, 5.0 N.A. is throwing a P0174 "system too lean bank2. It has a very rough idle.

Seems like it could be a vacuum leak, an O2 sensor a MAP sensor and various other things. Is there a most likely cause of the various possibilities for a 5.0 2011?

thanks!
ken

 

anywhere and everywhere. From the dip sticks to the flying saucer on the valve, cover to the intake, air tube to the math sensor to that intake gaskets to the throttlebody to the hoses to the O-rings wherever they may be. You’ve got a leak somewhere.

 

Ah excellent, chasing leaks - I so love that!

I saw someone recommending flooding suspect areas with propane, sounds a bit dodgy, how about argon?

 

Argon doesn't burn so ought to work - a bit, as it won't burn whereas extra air getting in has some O2.

Don't flood with propane! Spray sparingly.

Watch STFTs - don't listen for rev change.

 

Had a chance to do a little debug with the OBD scanner today.

Yes, definitely looks like a leak. Thankfully doesn't look like the inlet manifold gasket, as getting that off is a pita (yes, I had to do the whole cooling system pipe/hose replacement a few years back)
Fuel trims are bad, 25/30. They get better with engine speed (to the point of being good) and don't get better with engine temp. Both point to some random leak, but not the inlet gasket.
Wish I owned a smoke machine.

Ugh........

 

Crap! Just found out that I can buy a smoke machine for around $100. As Butthead would say "I'm there, Dude".

edit: OK, I spent $200. Still less than 1 hour charge at the dealer I expect.

 

whatd you get? I got one of these.

 

I got this one. Generic Chicom unit, but decent features, on board "compressor", and a bunch of useful plugs etc for plugging up parallel paths -like the fact that we have two engine air inlets on the XF. Seems like plugging one of those might be handy, of course I could've used a rubber glove but still .........under $200 delivered isn't so bad.

 

With the code your getting it's pointing to only one side of the engine? Normally we see 171 and 174 codes which says both sides of the engine are effected.
I would look closely at bank two intake tract plastic ducting. Check your manual but I think bank 2 is the drivers side. I get confused because Jaguar numbers their cylinders differently.
I found it! See if the attached document helps?

These are VERY common source of air leaks and it's getting worse because of the plastic breaking down over time.

Also do check the air box and make sure it's assembled correctly and that you don't have something simple like the air box lid leaking?
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It's strange, the other day I swapped the MAF sensors over, and it threw a 171 code. I thought "Aha, it's the MAF". Swapped them back and drove it again, and since then it's been sending 171 and 174 codes. Coincidence maybe? Certainly the fuel trims show both sides equally bad at idle, around 25% STFT and 32% LTFT from memory.

Regarding the airbox - that's upstream of the MAF, I don't think a leaking airbox would throw a 171/174 code?

I will remove the large inlet hoses and check them, although I didn't see anything. Mileage wise, this car only has 56K miles on it, so it's perhaps not as bad as some 2011s with more heat cycles on it?

 

A tiny gap you can't see with the eye can be a huge leak so don't be surprised if all looks OK.

A bad / dirty MAF can for sure cause problems, as the Jaguar PDF on codes says.

 

It' seems strange that there are two MAFs, instead of one as with the MAP. When my OBD reads out the MAF in live data, is it the average of the two or what?

I could find no guides to PO171 or PO174 in the XF workshop manual, is there another publication I should know about?

 

Yes the plastic bellows with the ridges hides cracks very well.
Not really these are probably the two most common codes after coil miss-fires. So lot's of information about what causes it.
I have SDD and I can read both of them individually? I think it might be a limitation of your device?
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From JagRepair.com - Jaguar Repair Information Resource

 

Smoke test was hopeless with the airboxes sill on the car. Remove the air boxes, plugged one side and smoked the other side was necessary.

It LOOKS like the intake manifold is leaking from the front. I guess the STFT/LTFT not improving with engine temperature gave me a false sense of security that it was not the manifold.
I will need to be darned sure it is the manifold before I remove it. I remember when I did the coolant pipes/hoses that it was not the easiest job in the world to remove.

When I did the coolant hoses I obviously HAD to remove the coolant, I don't recall if that is also true for just removing the intake manifold? Guess I'll find out.

 

Curioser and curioser.

I removed most of the front end plumbing, and the leak seems to be behind the water pump/belt tensioner area??? Too low down for the intake.
What could possibly be there?






The picture doesn't show the volume of smoke, it's pretty high, in fact the smoke machine generates no pressure on the gauge indicating a pretty bad leak.

 

Can't say? Anyway to get a picture of the smoke coming out?
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Here's a vimeo video

https://player.vimeo.com/video/809440682?h=385c08188e" width="640" height="564" frameborder="0" allow="autoplay; fullscreen" allowfullscreen>

 

I think your link is bad. Circle on the pic where you see the smoke

 

Try just the first part, should work

https://player.vimeo.com/video/809440682?h=385c08188e