Doesn't look like an air leak. (The LTFTs would be much smaller at revs for that.)

MAF must be a possibility.

 

Yes, the MAF was my initial suspicion also. I did buy and fit a new MAF and this did improve things a little, but there is still a long way to go. I found a tabulation of rpm vs MAF readings here: JagRepair.com - Jaguar Repair Information Resource.

So far I have only been able to measure in Park and my readings are reasonably close:

Idle: Spec 5.1 gm/s
Measured: 6 gm/s

2500RPM: Spec 17 gm/s
Measured: 14.7 gm/s

Not sure how to measure in Drive. When my OBD scanner is in place, the gearshift is locked (having the scanner on also throws a few spurious electrical faults which disappear when I disconnect the scanner).

Also, this engine seems to have no EGR, so it can;t be that.

I would like to check the MAP sensor but I can't find out if I have one and where it is located.

I will also try cleaning my injectors with BG44..maybe I got some dirty fuel.

 

Here's a recap as I am still getting P0171 and P0174, plus intermittent RP

1. Replaced part load breather hose (small leak)

2. Removed and checked intake elbow for leaks (none)

3. Monitored STFTs and sprayed brake cleaner everywhere. No vacuum hose leaks found. minor sensitivity around one of the intake manifold ports.

4. Measured vacuum at fuel regulator as 17 in HG. About OK

5. Replaced fuel filter

6. Measured fuel pressure at Schrader valve on fuel rail at 43psi at idle. About OK.

7. Replaced MAF sensor as it seemed to be under-reporting air flow.
Now measures as follows
Idle
STFT1 0
LTFT1 +18.7
STFT2 0
LTFT2 +18.7
MAF 3.7 gm/s

at 2500rpm
STFT1 0
LTFT1 +19.5
STFT2 0
STFT2 +19.5
MAF 12 gm/s

8. Removed and cleaned intake manifold and throttle body base. Looked for manifold cracks. Cleaned all injector rings. Cleaned intake ports on head. Replaced all gaskets. Replaced and torqued manifold.

9. Engine fired up first time, which was good news!. The bad news is that the fuel trims were unchanged. No evidence of vacuum leaks anywhere (brake cleaner/STFT monitor method).

So where do I go from here? I've learnt a lot doing the investigation so far, and really appreciate the ideas and wisdom from this forum!Thanks to all who contributed!
However, aside from learning about my car, I am really not much further forward.
Is it time to go to a Jaguar specialist for a diagnosis?

 

Double check that your fuel injectors are fully seated. The larger outer fuel injector seals in the intake manifold actually seal vacuum and should be compressed a bit. You can tap them in gently with a wooden dowel and a hammer. Just bolting on the fuel rail does not set them deeply enough in the manifold.

 

Did you do a hard reset?

 

Gus.... yes did a hard reset also. Still getting P0171/P0174 after a bit of driving.

WhiteXKR...yes, I noticed that the injectors did not seat properly first time when clamping them down with the rail, so ended up taking a great deal of care getting them seated properly. I'm confident they are now well seated!

Does anybody think my problem may be related to faulty O2 sensors? It would seem unlikely to me that both would fail simultaneously, and I have never had just one bank reported lean. Both banks or nothing.
I confess to not fully understanding how to determine if the O2 sensors are working properly or not.

 

Do a smoke test on the car first!

 

This problem arose a year ago, but I can now report that it has been fixed! Others may be interested in the final resolution, so heres's a quick recap of the problem and all of the steps taken to resolve:

Original Problem
Check Engine Light and intermittent Restricted Performance
Diagnosed as Running Lean Both Banks - OBD P0171 & P0176

Steps taken:

1. Replaced part load breather hose (small leak)

2. Removed and checked intake elbow for leaks (none)

3. Monitored STFTs and sprayed brake cleaner everywhere. No vacuum hose leaks found. minor sensitivity around one of the intake manifold ports.

4. Measured vacuum at fuel regulator as 17 in HG. About OK

5. Replaced fuel filter - original was pretty dirty.

6. Measured fuel pressure at Schrader valve on fuel rail at 43psi at idle. About OK.

7. Replaced MAF sensor as it seemed to be under-reporting air flow. Purchased an after-market sensor on ebay for $45. It made little difference to the Fuel Trims, so apparently was not the problem!

8. Removed and cleaned intake manifold and throttle body base. Looked for manifold cracks. Cleaned all injector rings. Cleaned intake ports on head. Replaced all gaskets. Replaced and torqued manifold. Good project!

After all of this, the problem was essentially unchanged. I managed to convince myself that maybe buying an after-market MAF Sensor may not have been a wise move, and that this may still be the problem. However I couldn't bring myself to spend the $200+ on an OEM MAF sensor, so I looked at ebay again. This time I found a sensor claiming to be compatible for $26 and free shipping. No brainer at that price even if it made no difference, so I bought and fitted it.
Problem fixed!!! Measured fuel trims and it is actually now running a bit rich (~-10), but does not trip MIL and RP. Have driven a couple of thousand miles since then just to make sure all is OK, and indeed all is OK!

I think I was unlucky with my first aftermarket MAF sensor being almost identical to the original (faulty) sensor, which threw me off track. But I also think I was just plain lucky that the second MAF sensor actually fixed the problem.

It seems to me to be likely that the reason that Jaguar charges so much for MAF sensors may well be that they preselect MAF sensors within a very tight tolerance. If you just buy cheap ones on line, they may work, but they may not. And they are in any event unlikely to give you "zeroed" fuel trims.

Wouldn't it be nice if there was a way to program the ECM to compensate for MAF sensors which under/over report air flow?

Hope this helps someone!

 

Many years ago I worked for a company that made Bottle Inspecting Machines that used Photocells. The design was such that the Photocells had to meet a certain spec.

It was cheaper for us to buy the untested Photocells and test them ourselves, rejecting 2 out of 3, than have the Photocell Manufacturer do the testing.

If one of our Customers bought the Photocells himself, there was a 2 out of 3 chance that they wouldn't work.

Sourced from our spare parts department (at a large price of course) they would work.

 

Happy to see you got it fixed. Please fill me in on the MAF that worked and a link to where you got it.

 

Got the MAF Sensor on Ebay. Not sure if the link still works, but found it at:

Mass Air Flow Sensor Meter MAF Jaguar Subaru Mazda 197408 0010 New | eBay


The vendor was mpgautoparts at
Mass Air Flow Sensors

Price paid was $26.99

As I said in the post, I think I was lucky to get a MAF Sensor that worked within Jaguar's spec range!

Good Luck!