Guys,

I am driving around 200 miles daily on my X-type at around 75 to 100 MPH using the cruise control (on/off due to slower drivers), I always make sure to plug the OBDII reader while driving and check the readings when I park the my car at end of the journey.

I've noticed that the latest LTFT1 & 2 are showing -17.97% & -15.62% respectively, but my STFT1 & 2 are 4.69% and 2.34% at idle. on the other hand, almost each time I park the car and check the readings of fuel pressure is something between 47 - 58.5 PSI. The car overall consumes a noticeable amount of fuel. I can see that the readings are off the limit.

I've recently changed the air filter, spark plugs, fuel filter & 3 x used ignition coils until I receive the 6 x new ones (feeling that the coils might have a hand in this?maybe producing weak spark?)

No codes of any kind are popping up.

Any comment would be appreciated to sort this out.

 

 

How much is a "noticeable amount of fuel"? If you are traveling 100mph your mileage would definitely not be that high, but what would be considered "normal" is hard to say as I bet few X-Type owners are able to travel at those high of speeds for extended periods of time. Or has the average miles per gallon gone done recently?

 

Iownme, he's in Dubai

 

 

@iownme - haha living in Dubai, major highways are with around 90 MPH speed limit, but the route to my work location merges with a 100 MPH speedway for 30 mins, the Jag is really quite and stable on this speed!

@ Alfadude - when I first bought the car, it was almost 1/4 of the tank to drive one way and LTFTs were actually around -/+ 0 %. Now, I it consumes almost 3/8 of the tank going one way! but the instant MPG readings are around 18-24 at 100 MPH.

I have to admit that when I got the car, I ran the scanner and got few codes for misfiring, ignition coils and MAF (cleaned it only) - all have been rectified and no codes are popping up.

This Friday, will start the diagnosis just to be sure that this is normal, will re-clean the MAF & air filter, check if there is a leaky/stuck injector. Not sure if the fuel pressure numbers are within the limit? as I am not willing to start throwing parts in it like a fuel pump.

Any suggestions or tips would be really appreciated.

 

it actually sucks a noticeable amount of fuel in traffic, with normal accelerating/decelerating and fuel range drops rapidly.

 

The best thing to do is check your actual miles driven and then see how much gas you actually use. If you get anywhere close to 24 mpg going 100 mph for an extended period I would think you are doing very well. Also, the gauge itself is not 100% linear in how it registers. Will take a longer time to go from full to halfway than it takes to go from halfway to empty. The instant readout on the dash is not necessarily a good barameter of your MPG. You really need to monitor it over a longer range as even slight decelerating and accelerating could show some big swings.

Has the MPG recently changed, like was it like 27 before and now it is at 20 now?

 

@Alfadude - I agree with you. Overall, the avg. MPG using the OBD reader is showing me around 25, it was roughly 27.

The fuel consumtion on the highway makes sense, but when I stop on a traffic light or just drive in traffic, it absorbs more than before.

Also, my concern is the LTFTs, are they off the limit? Fuel pressure readings? today, I checked the readings after I parked, the fuel pressure is showing me 43 psi, yesterday was 56?

I am going to replace the ignition coils with the new ones, Ive read somewhere that a low quality/old ones can produce spark, but a weaker spark resulting in more fuel consumption? is this a correct statement?

Anything to worry about or to look for?

Thanks!

 

 

It's a crazy thought, but check your air filter. Mine was so bad it looked like liquid tar covering it. Replaced it and fuel trims improved and gas mileage (actually measured gallons/miles) was better. I have monitored the on board m.p.g. And avg. M.p.g. In mine for over a year and a half versus the actual miles driven and gallons used. The on board has never been close to the actual useage. By close I mean from 2-5 m.p.g. Off. And bear in mind an OBD reader gets it's info from the ECM, so same as the dash display.

 

Your car is getting too low amount of air. I would also spray throttle with break cleaner.
Another restriction could be partially clogged cat converters.
MAF has to cleaned also.

 

Thanks guys,

I am waiting for the coils to be delivered, there is no harm in re-cleaning the air filter (although its brand new), MAF and spark plug again since I will be installing the coils and new valve cover gaskets soon.

When I first got the car, it had a P0102 code with "Mass or Volume Air Flow Circuit Low Input", then I cleaned the MAF and the code disappeared.

Its weird that no codes are popping and the car drives great. Now, the Long fuel trims on both bank 1 & 2 have crossed -20%.

Thanks.

 

get an ultragauge and look at the fuel trims while driving, it also allows the eml to be cleared while driving if it pops up.

 

Thanks for the input guys.

Ive noticed that the inlets for the air filter box are dis-connected/broken, and the bolts holding the air inlets are loose resulting in them being pointing somehow downwards. Not sure if this would have this major impact? I will fix it again and make sure the inlets are pointing as they should and fully connected to the air box. Will reset the ecu and drive the car to see if there is any difference.

Thanks

 

MTypeX: When you clean the MAF, be sure to clean the 'hidden' wires pictured in this post: https://www.jaguarforums.com/forum/x...2/#post1896030