Yes this is correct!

 

Okay, thought so, I will try cleaning the MAFS again but I have cleaned it before so I'm not sure it is going to help.

My Bluetooth tool is arriving UPS today so I should be able to read fuel trims! What kind of fuel trims should I be looking for?

 

LTFTs near zero. Hot engine, parked, at idle & at 2500rpm.

 

Okay... Higher then they should be? What does all this mean?

Parked, 2500 rpm, engine at operating temperature
ltft1 14.02%
ltft2 19.53%
stft1 0-2%
stft2 4-8%

Parked, idle, engine at operating temperature
ltft1 19.53%
ltft2 19.53%
stft1 18-20%
stft2 19-21

 

Hi.


To explain fuel trims, you will find a good article searching in this forum, explaining it a lot better than I can do.


You, or more correct, your car has a lean condition. This is caused by not enough fuel, or too much air. The ECM is compensating for this, based on readings from the O2 sensors, by adding more fuel. When this add gets above a certain value, it will flag a code. (P0171 and P0174)


I think you have an air/vacuum leak somewhere. What to check:


Air intake elbow.
Part load breather
Full load breather
Throttle body elbow air/vacuum connections. (Two on each side)
EGR connections including pipe ( If installed )


It can be more solutions, but this is what I can take from my memory right now.

 

'oyster' is right on

These two threads and their included links describe fuel trims pretty well.
https://www.jaguarforums.com/forum/x...s-help-110289/
https://www.jaguarforums.com/forum/x...racked-112603/

 

Odd - very - to have identical LTFT at idle & fast revs. Re-check as it "just cannot be"!

 

I did hear a vacuum leak this morning and easily found a small hose near the throttle body disconnected. This hose was connected Thursday so I probably knocked it off yesterday while playing with it. After reconnecting I sprayed starting fluid on all of those parts with no noticeable engine change. I also smoke tested from MAFS through intake tube, when there was no leaks there I attached the smoke tester directly to throttle body and still no leaks. I know the smoke test is working because if I disconnect a line smoke comes right out.

Now my readings after running the engine for 30mins at operating temperature.
Ltft1 14.02% 2500rpm
Ltft2 19.53% 2500rpm
Ltft2 10% 2900rpm

Ltft2 does not change until I hit 2900rpm ... Could this mean I have a blocked fuel injector or bad MAFS?

 

Hi again.


The key to finding the problem is to be systematic and keep it simple.


At the throttle body elbow below the throttle body check
on the right side two vacuum lines connected and tight
and
on the left side part load breather hose and one vacuum line.


If EGR installed check all connections.


Now, with a warm engine increase RPM from idle to 2500 rpm while watching fuel trims. If they decrease, especially short term, it is very likely you have an air/vacuum leak.

 

Thanks everybody for helping, please bare with me ha ha. All of those connections are secure. Egr is installed but again everything connected to it seems secure.

I switched apps, I think the one I was using was giving me incorrect readings. It looks to me like they are decreasing...


Idle
Ltft1 19.5
Ltft2 19.5
Stft1 7.8 to 15.6
Stft2 7.8 to 17.2

2500rpm
Ltft1 16.4 to 17.2
Ltft2 19.5
Stft1 -5.5 to 3.1
Stft2 4.7 to 10.9

 

See if this information helps you understand the fuel trims

Link JagRepair.com - Jaguar Repair Information Resource

Have any questions let me know. I hope this helps.

 

Hi again.


That looks like an air leak to me.


Understand you have changed the part load breather hose. Both this one and the full load breather hose should be changed anyway as they are in plastic and get brittle over time and crack. Their gaskets also dry up causing leaks.


The connection of the part load to the throttle body elbow, a T-piece must be tight.


Two vacuum lines on right side of elbow. One of them has e strange coupling and tends to leak.


Gaskets around the supercharger and intercooler. I don't know much about these as I have a normal aspirated myself.


Now, with the engine idling, spray carb cleaner on suspected leak spots while watching STFT for any change.


Be careful. The carb cleaner is flammable and you don't want to set your engine or yourself at fire.

 

Does anybody know what supercharger specific parts/gaskets could cause this problem?

The full load breather hose is on the left connected to the intake tube correct? Yes that is brand new. Part load breather hose is on the right, same kind of connector but longer correct? That is brand new as well. The intake tube is also brand new.

The T-piece on the part load breather hose seems tight, the two vacuum lines on the right side of the elbow seem tight as well.

The engine is hot now as I was taking the readings after I put the bottle of gumout in it. Just slightly lower readings at 2500rpm. I will try the carb cleaner when the engine has cooled off.

 

The full load breather should be on the right when viewed from the drivers seat, which is the proper orientation for describing locations. I assume you are referring to position as viewed from the front?

 

Yes I was talking about viewed from the front.

 

Are 2003 xkr MAFS compatible with 2000 xkrs? They are different part numbers but look almost identical. A family member of mine has a 2003 so I swapped the MAFS to see what kind of readings I would get. And here is what I get:

Idle
Stft1 3-5
Stft2 8-10
Ltft1 19.5
Ltft2 19.5

2500rpm
Stft1 -15 to -20
Stft2 0 to -2
Ltft1 10.9
Ltft2 2.3

The readings still don't seem right, but they are significantly different and I haven't got a check engine light/restricted performance "YET". Any thoughts?

 

Dropping like that means an air leak.

 

After cleaning the original MAFS again and reinstalling my ltft2 does change when accelerating to 2500rpm! I'm also back to only receiving a p0174 code. Maybe the dirty MAFS had me looking in the wrong places for the leak. I will search the forums for leaks related to just p0174 but feel free to post if you know of any...

 

UPDATE: The smoke test was not working because there was a leak on the EGR pipe which is obviously past the EGR valve and the EGR valve is closed until it gets hot if I understand correctly. The old school starter fluid method of locating the leak was not working because it is covered with a heat shield so I could not spray or see it. I replaced the EGR pipe, $160.... cleared the codes and have been driving the past 30-40mins. Everything was fine until I got stopped at a train for about 5-10 minutes at idle and the restricted performance/check engine light popped on.

P0174

Fuel Trims:
Idle
LTFT1 19.5
LTFT2 19.5
STFT1 5.5
STFT2 16.4

2500 RPM
LTFT1 2.3
LTFT2 7.0
STFT1 10.0
STFT2 20.0

The stft's are not decreasing but increasing now. The ltft's still do not change from 19.5 at idle. Do I still have a leak or another problem?

 

ltft drop with revs so you have an air leak