Hello, I have a 2015 Jaguar XFS AWD (3.0 Super-Charged Petrol Engine) that is parked at my parents house (In a closed garage). I requested my dad to start it up once a week to keep the car from draining its battery or developing any issues. Two weeks ago my dad started the engine at around 9 PM and forgot to switch it off as he attended a phone call. He returned to the garage at 5 AM and could smell light exhaust fumes. He reported the car used a minute amount of fuel (about 10%) and the engine wouldn't start. He tried later in the day and the engine turned on though it felt "choked", he then pressed the accelerator to clear out the "clogged" exhaust and idle and exhaust tone was back to normal.

Upon my visit to my parents house last week, I took the car out for a drive on the highway and tried the "Italian tune up" just for good measures. The car was used for the entire week I was there and I noticed the fuel economy shot up from 13 L/100 KM (~18 MPG) to 24 L/100 KM (~9.8 MPG). I took the car in for an oil change, air filter change. The fuel economy has dropped down to 18 L/100 KM at best, driving on the highway and goes up to 19 L/100 KM in stop and go traffic.

The car is still under warranty, so I took it in to the dealership for a check-up and was told that everything is fine. "18 L/100 KM is due to my driving style and it's completely normal - they could not find any faults". I am under the impression that letting the car idle in a closed space took a toll on the engine, maybe the spark plugs?

I would appreciate any input towards fixing this issue.

Cheers!

 

You don't say what engine you have, this makes a huge difference.
I suspect you have the 3.0 V6 diesel and if so you could have a partially clogged Diesel Particulate Filter (DPF) due to the period of extended idling, which would explain the poor fuel economy.

 

Hey, the X250 AWD was only available in the 3.0 S/C petrol, I didn't feel the need to specify, sorry about that.

 

Sorry, I assumed you were from somewhere in Europe (coz you talk in l/100km and not MPG) and I know the Euro 2015 X250 XFS came with either the 3.0 diesel or the 3.0 petrol, and I also assumed that the AWD version came with either engine but it seems I was wrong on that last bit.
Which means I also have the same engine as you and I have no idea why you now have such poor fuel economy!

 

Thank you for the response OzXFR, I'm from Canada. I'm trying to tie the high fuel consumption with the lengthy engine idle though I can't find any information. Maybe they are unrelated...I've always used Premium fuel with fuel stabilizer and occasional fuel octane booster/cleaner. The car is developing other small issues but I'll share those in a different post. Mind I ask what you're getting in the F-Type?

 

I have averaged 9 litres/100 km over the 2 years and 8 months I have had the car, about 25,000 km.
50% very short trips of 1 or 2 km, 40% slightly longer trips of 15 to 20 km and 10% longish trips of 100 to 400 km. Always in Dynamic, not "driving Miss Daisy" but not (quite) driving it like I stole it either and the last 16 months with the VAP tune and crank pulley putting out 450 bhp. And nothing but 98 or 100 RON petrol.
But of course the F-Type is a much lighter car than the XF AWD so there is no way you will ever get the 9 litres/100 km I am getting.
A much fairer comparison would be with my old XFR, similar time span, mileage and driving pattern (maybe a few more longer trips), I averaged 13 litres/100 km in that car.

 

Clear the trip computers and actually drive the thing. After a few tank fulls the real average will show up, the owners manual has more details on how this is calculated. The engine choked on its own carbon dioxide.

 

Thank you for your response. Like mentioned above, the car was used throughout the week I was there. I went by 4 full tanks, averaging 18 to 20L/100KM. I reset trip B every time I filled up, while leaving A for long term reading. Car is covering 340-380 KM/Tank. The car started off with a high L/100KM reading as expected of a reset trip meter, and gradually settle to the 18L/100KM mark.

I have also started noticing an unusual sound when turning off the engine (on the outside), it sounds like a lawn mower shutting off, otherwise it sounds fine. My local Jaguar dealer said "thats nornal".

Do you reckon spark plugs might be at play in regards to poor fuel economy? I'll be getting those changed next I'm there.

 

Sounds like it could be the classic SC coupler / torsion isolator spring "clonk" on engine shut down.
Heaps of threads and posts around here about a worn SC coupler and how to replace it, search is your friend.

 

Noted, so its NOT normal. I'll look into it. It has not affected anything as of yet. Do you reckon it should be covered under Jaguar warranty? It is a matter of convincing the dealer that it isnt normal.

 

It is covered under the factory warranty, not sure about CPO though.
There is a TSB for it where under warranty and therefore free of charge the dealership will change the entire SC snout (where the coupler sits) for a new one. Again, search is your friend.

 

Okay, thanks. I'll bring it up to the tech since my car is currently at the dealer for a backup camera fault. They are hell-bent on charging $250 for every little inspection. "Please check the issue with the backup camera" , "....that will be $250, and if its covered under warranty, the charge will be waived".

 

It appears that supercharger coupling is indeed bad and will be covered under warranty. That wouldnt explain the bad fuel economy though, would it? Ill be getting carbon cleaning done for a good measure aswell.

If anyone had any idea what might be causing those outrageous fuel consumption readings, please let me know as the dealership I'm dealing with cam not pin point any fault with anything, and I have to explain what might be wrong - thus resulting in any effort made to diagnosing the issue.

Thank you!

 

A worn SC coupler does not cause poor fuel economy in and by itself, something else is wrong.
Surely the dealership should be able to pull up some codes using their SDD equipment and identify the fault(s) or at least narrow it down a bit.

 

The dealership service advisors and techs are hopeless. Reason I don't take it to another Jaguar dealership is due to the loyalty program: Which basically means no loaner (They prioritise customers who purchased their vehicle from that very dealership), long wait time to get an appointment (2-3 months). Upfront diagnostic charge of around $300 is Toronto area.

I've hooked up my personal OBD scan tool, but couldn't find any error codes, though It isn't a super advanced tool to begin with. I'm really hoping that changing out the spark plugs for new ones and chemical carbon cleaning of the intake makes a difference. My last guess would be a bad fuel pump, nothing else comes to mind.

 

Allright from the original post it sounded like one of those cars being stored and just idling will definitely show a poor fuel economy calculation. European luxury cars really hate sitting and will punish the owner with high maintenance bills.

By all means, if you have warranty then have the dealer verify everything that goes into air/fuel ratio, mention fuel trims and they should get the hint. If it is really off then there is a possible vacuum leak and the computer dumps more fuel to compensate, just one example. This may not necessarily show up in codes so insist that they run a smoke test. If you don't get anywhere, try another dealer location that may have more competent techs that don't try to pretend that kid of fuel economy is normal.

 

Noted. Yes, the car does sit inside the garage unused for most of the time as I'm currently using my winter vehicle year round. Lower insurance, good on fuel and I'm less anxious about pot holes in my University town.

The fuel economy numbers shown above were take after oil change, new air filters all around, using up the entire tank and refilling it with fresh fuel and fuel cleaner. The numbers dropped from mid 20s (L/100KM) to to low 20s/high teens. I drove the car roughly 600 KM in that week and is currently being used by my family member for daily commute to collect fuel economy data.

I should mention, the car has had two coolant leaks in the past 6 months. Both involved changing out the reservoir or one of the tubes connected to it. The leak was tested via compression test. As far as "smoke" test and vacuum leak is concerned. Would these involve a test on the fuel lines and or fuel pump or maybe even the fuel tank to check possible leaks (if there were any it would be more obvious I reckon)? I want to take note of any possible issue and have enough knowledge about it to reason with the service advisor.

I appreciate your time "Litteredwithfaults", I reckon that name is better suited to my XF.

Cheers!

 

I searched up smoke test and vacuum leak. It appears they're targeted towards the intake system and not the fuel system.

1) Air/fuel ratio diagnostic via scan tool - should raise concern if the numbers are off the norm.

2) Smoke test followed by diagnostic above, should find any leak(s) in the intake.

 

same car (2015 xf 3.0SC AWD) highway 110km/h on crusise averages 7.2l/100km city driving with 35km/h average speed 13.8l/100km

hook OBD tool and measur MAF values (should be around 4grams at idle) also engine load in %. should be around 10% at idle. also look for long term and short term fuel trims.

 

~13L/100KM is about what I used to get. Mainly city driving. Even that, I used to think was a bit high comparing it to my second car thay is a 2011 Lexus ES 350 with the 3.5L N/A engine averaging 9L/100KM city driving that I got 6 months ago for winter use.

I've just placed an order for a proper OBD scan tool and will provide an update this coming Saturday when I'm due to see my parents for the weekend, and go over the maintenance plan.

Thank you for your response Elviukai!