Note for clarity: I'm not sure if the car has a separate MIL-esque light besides the "reduced performance" and "limp mode"/"door open" lights. I might incorrectly be reffering to the "reduced performance" light as the MIL light.
I am reffering to the "rev limit at 3000 rpm" yellow light.

Yes, the yellow light is a very recent occurrence, I think it started coming in since last weekend.

The only registered code is currently P0171, besides the Long Term trims, the freeze frames don't show anything special.
DTC that caused required freeze frame data: P0171
Fuel System 1 Status: CL
Fuel System 2 Status: CL
Calculated LOAD value: 14.1%
Engine coolant temperature: 93C (199 F)
Short Term Fuel Trim - Bank 1: 3.1%
Long Term Fuel Trim - Bank 1: 18.8%
Short Term Fuel Trim - Bank 2: 1.6%
Long Term Fuel Trim - Bank 2: 16.4%
Fuel Rail Pressure (gauge) 384 kPa
Intake Manifold Absolute Pressure: 45.0 kPa
Engine RPM: 608 / min
Vehicle Speed: 0 km/h
Intake Air temperature: 13C
Air Flow Rate from Mass Air Flow Sensor: 5.73 g/s
Absolute Throttle Position: 2.7%

.I reckon the P0174 isn't that far behind

An almost textbook definition of a vacuum leak.

 

lean code = automatic RP.

you need to smoke it with smoke machine. aftermarket cats can also mess with your trims.

at idle makes me think it’s a vac leak

 

Yes, find & fix the leaks.

If still a problem:
1. check for PCM codes (basically Pxxxx ones)
2. check the other modules
3. check all OBD monitors are set (shown by pending P1111) else which are not

 

Hi

I have P0171 and P0174 bank 1 and bank 2 too lean - I have various screen shots of the LTFT and STFT - you appear to be
knowledgeable re these issues.

If I were to send you my readings - do you think you would have time and be willing to have a look over them and give me
any advice. The XF V6 petrol 3.0 is going in for a "smoke check" on Tuesday.

many thanks in advance

kind regards

Stuart

 

The problem is your readings don't help? By that I mean yes they point to a problem but the numbers are of no help.
Follow the advice given above especially xalty.

Report back on the smoke test but be aware that might not solve it either. I usually see the smoke test done for EGR leak codes but let's see what they find.

I recommend to monitor fuel trims in real time and spray carburetor cleaner or Propane around the likely leak spots.
Also have you inspected the plastic ducting on the intake system? Go over these items in fine detail. Especially the accordion type parts. It's very easy to have a crack in the bellows and not see it.

Thank you for the car information as we usually play 20 questions with people to get to that point!
But you jumped into a thread about an STR which you don't have so be careful as not everything applies equally to the V-6 and the SC V-8.
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(somewhat) sorry for necro'ing the thread.
But life got in the way.

Some updates:
- Did a smoke test, the aluminium intake part taken from a Land Rover had a crack, so I reverted to the stock intake.
- the brake booster... connector (to vacuum manifold?) was indeed leaking and has been replaced by a garage.
During the same visit they found another leak on a 'gasket' forgot to ask which. So they replaced it.

They smoke tested the car afterward and couldn't find any other leaks. (Said visit was about 2 months back)
Up until this week the P0171 was a rare occurance, but now everytime I calmy bring the car to a stop (let off the gas, bit of braking), and I'm standing still for about 5 seconds the P1071 is back.

When I resume driving and keep the car above -/+ 2000 rpm for somewhere between 20-30 seconds the P0171 is 'cleared' but bringing the car to a stop brings it back again.

What would you suggest,
re-run the trims test for vacuum leaks?

The garage checked for leaks but the error seems to come up when making low RPMs and resolves itself when making high RPMs..

Sidenote:
It seems the error is easier to retrigger when the car is at operating temperature. The first 5-10 minutes of a drive I hardly ever see it.

 

This indicates to me you have a tiny air leak somewhere. Small enough so that it affects the LTFT enough when the MAF is recording very low airflow. At higher RPM the effect is less & not enough to trigger the code. If you use a scanner look at the flight recorder data stored for the code. I'm guessing it will show LTFT above 20% which is what triggered the code. If it's on one bank, you can narrow your search down to there, if the other bank is close to it, it's before the air flow divides.
You may also plug your scanner in & go for a drive with the LTFT up & showing live data. As you're driving I'd expect to see the trim(s) dropping.
As suggested, spraying a liitle propane in areas is a good idea & you can narrow the area to concentrate on more effectively than a smoke test alone (that may not find a miniscule leak).

 

So, I figured the garage fixed the leaks (as I asked them to) and in my mind had 'more faith' in them than I had in you, but seeing as you were trying to help me I was going to take the measurements to prove you wrong, and show some decent idle trims.
Boy was i wrong...

I cleared the errors yesterday so all OBD monitors are (still) pending, so all errors I have are P0171 and P1000.

After checking the errors I opened the live data for STFT/LTFT for both banks and started testing.

As the say, 'A picture is worth a thousand words.' so below I've added the pictures of my tests at idle, 1500 and 3000 RPM.
And these pictures sure do tell a story (too bad I'm not sure what they're telling me though...)







18.8% Bank 1
12.5% bank 2
Ouch..

After idling for a bit I tried testing at 1500 RPM:

1500 RPM. better, but still terrible..
14.1% bank 1
6.3% bank 2

After running on 1500 RPM twice, I tried 3000 RPM:

3000 RPM, bank 2 is getting there, bank 1 is still far of.
10.9% bank 1
2.3% bank 2

Below a summary of the 3 tests, the STFT on bank 1 is pretty chaotic..

Both 1500 RPM and the 3000 RPM measurements with their LTFTs.



Bank 2 (blue) has a decent sine wave.
I'm not sure wth bank 1 is doing though..

 

Do what Robinus suggested. Let the car idle a bit to settle down. Then watch the fuel trims as you spray Propane around the engine area's.
All those numbers tell you is you have a vacuum leak.
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This might have been covered but closely look at the air intake tubes that go into the air filter box and out to the throottle body. Anything rubber or plastic. There is also a rubber coupler that goes between the throttle body and the bid metal intake tube that is in a hot spot and can crack

 

I'll try to get my hands on some butane/propane tomorrow and spray down every part I can properly reach, starting at the MAF and going down as close to the cylinders as I can

 

As you spray, watch the STFTs. They typically react instantly and often wildly.

 

And forget the graph setting. Just use the numbers, it's a lot easier to read.

 

I ran the test with a new bottle of butane in a blowtorch, it was belching nice clouds of butane and freezing stuff.
I focused mostly on connections near the throttle body and it's rear/behind (the busy place with all the gaskets).
The rubber connector between the black (metal) intake pipe and throttle body is very flexible without any signs of cracking or drying, same with the one between the intake 'accordion' and the metal pipe.
Spraying down the intake 'accordion' didn't net anything either (which I had kind of hoped..)
The rubber hose a little bit in front of the throttle body (I think it's the SC bypass hose) looks quite discolored, but hosing it down with butane didn't yield any certain changes in STFTs (0.8-1.6% at best which is mostly likely the engine just doing it's thing)

The best I got was -3.4% on STFT (both banks) .

The only errors present in the engine module are P0171 and P1582 (for some reason B0171 and B1582 aswell).
Fuel pressure (from sensor reading) at idle was 3.8 bar (a little high?), for our imperial readers, 3.8 bar. Could be normal but I wouldn't know.. the specs says it should be around 3.3
The MAF is not that old (replaced it somewhere earlier in this thread, so 2 years max?),
fuel filter has been replaced about 1-1.5 years back, air-filter 2-2.5 years (K&N oiled, cleaned a year back)
what else.... plugs and coils aswell..

Honestly, I myself am edging towards the injectors being the problem, but I'll supply any info you could want/need to prove me wrong

 

LTFT2 comes down quite well when revved but LTFT1 doesn't so you may be looking at 2 problems: a leak affecting bank2 and something else for 1 (aftermarket cat?).

Are the O2 sensors the right ones, so we're not worrying about them?

I suppose persist with propane or try a smoke test.

 

Or more than one leak.

 

On the O2 sensors,
I've never touched them myself.
Bank 1 sensor 2 has been replaced about (twice) about.. 3 years back.
But nothing aftermarket or the like.
Always had the garage replace them.

I've had another garage look for vacuum leaks aswell but they reported they couldn't find anything either.

In the meantime I've ran a smoke test aswell but no visible some came out anywhere, but I've gotta note, his smoke machine seemed pretty weak (a smouldering cigar's worth of smoke) which is a real shame. I remember the first smoke test I had done some 3 years back, the smoke came belching out of every nook and cranny including the dipstick, I'll have to look for the receipt and have them run a smoke test again.

I read a fuel pressure sensor test online someone did on their X-type (probably works on all cars), which was unplugging the sensor which should revert the engine's injector timing to the factory's RPM/Air/Load based timing.

Doing this test the trims at idle improved significantly, both banks losing about 8% (bank 1 came down to 10-11% and bank 2 came down to 5%), so I figured (combined with the 3.8 bar at idle which should be 3.3) the sensor was bad.
As the readings seemed to stick on 3.8bar, whatever the load, I replaced it.
The new sensor seems to fluctuate some more (3.6 - 4.1 based on load) but sadly, no difference on the trims with the new sensor.

The cat on bank 1 has bad emissions and wouldn't pass MOT currently, that might be the cause for the big difference (No P0420 though), so when I send it out for refurbishing 2 years back they may have shafted me and put in either not enough material or some crappy aftermarket something..
Getting a second hand cat is virtually impossible. I got one shop in Belgium which quoted me about £700 ex VAT & shipping, no warranty which seems quite outrageous!

But that problem aside, I reckon both banks share a problem causing the 12% on bank 2, and 12% + (8% from cat?)

Any good ways to properly test the O2 sensors?

 

Swap sides with the O2 sensors & see if the trim results follow the sensors or not.

 

If you start your car from cold it should run in open loop. This means that it's not affected by the sensors, it's just running off the (richer) cold start fuelling map on the ECU. Once warmed up it switches to closed loop & the sensor data is used to adjust the running. If you've unplugged the sensors it's the same thing.
Reading now about your cat(s) it may be a contributing issue.

 

Don't know about the X-Type but I know for a fact that when my 2005 STR had fuel pressure regulator problems I did unhook it. The fuel system then default's to a constant and somewhat high fuel pressure so the car can still run under most conditions. Did not see any timing changes or anything else.

So that's another troubleshooting idea. Unhook it and see how the car behaves. When my FPR went bad the car was all over the place with no power and then fine power. When unplugged it pretty much drove normal. Note my car was throwing a P0193 code and there are a couple of more possible codes too? So you should have an error stored if the FPR is bad.

I did not see it but the 4.2L SC engine has a well known vacuum leak in the swivel vacuum connection on the SC elbow that feeds the PB booster. That was the cause of my vacuum leak. Might spray Propane around that area at idle and watch the fuel trims?
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