Birty Dastards Jeep Club

Tech Forum => Workshop => Topic started by: Green Jeep on March 12, 2013, 08:10:09 PM

Title: 11 mpg XJ Cherokee 4 litre 2001
Post by: Green Jeep on March 12, 2013, 08:10:09 PM

Struggling with poor mpg, truck is a daily ride and on stock road tyres, in the past I've had 25mpg and even 30mpg on a run in other stock Cherokee's.

Checked the obvious, plugs air filter etc, all fine, truck pulls well and runs smooth through all rev range and gears.

Had an emissions check done and passed well within limits so lamba etc working fine. Recent Mot so no brake binding.

Any idea's?

Thanks in advance Maf

Title: Re: 11 mpg XJ Cherokee 4 litre 2001
Post by: isle of man on March 12, 2013, 08:50:21 PM

Is it set to the other side of the pond MPG?

Title: Re: 11 mpg XJ Cherokee 4 litre 2001
Post by: Brynjaminjones on March 12, 2013, 09:40:24 PM

I can't imagine that would make too much of a difference, as I get a minimum of 16mpg on what I'm fairly sure is the US setting!

Title: Re: 11 mpg XJ Cherokee 4 litre 2001
Post by: isle of man on March 12, 2013, 09:50:27 PM

Fooooooook me!!! This i get from my G63.....

Title: Re: 11 mpg XJ Cherokee 4 litre 2001
Post by: Green Jeep on March 13, 2013, 12:50:21 PM

Quote from: isle of man on March 12, 2013, 08:50:21 PM

Is it set to the other side of the pond MPG?

Have gone on X amount of fuel in gives X amount of miles to work out 11mpg, computer shows 13mpg, so which ever is correct its still junk  :icon_sad:

Title: Re: 11 mpg XJ Cherokee 4 litre 2001
Post by: JamesH on March 13, 2013, 01:01:25 PM

cracked exhaust manifold??

Title: Re: 11 mpg XJ Cherokee 4 litre 2001
Post by: Green Jeep on March 13, 2013, 03:56:16 PM

Quote from: JamesH on March 13, 2013, 01:01:25 PM

cracked exhaust manifold??

Nope all quite

Title: Re: 11 mpg XJ Cherokee 4 litre 2001
Post by: bgbazz on March 13, 2013, 05:14:45 PM

Leaking fuel tank?

Title: Re: 11 mpg XJ Cherokee 4 litre 2001
Post by: Green Jeep on March 13, 2013, 05:32:10 PM

Quote from: bgbazz on March 13, 2013, 05:14:45 PM

Leaking fuel tank?

No stains under neath and it has the same amount of fuel after being parked up, really struggling on this one  :icon_sad:

Title: Re: 11 mpg XJ Cherokee 4 litre 2001
Post by: bgbazz on March 13, 2013, 05:42:20 PM

Ok, cross that off the list.

Title: Re: 11 mpg XJ Cherokee 4 litre 2001
Post by: Jonny Jeep on March 13, 2013, 07:18:25 PM

Coolant or intake air temp sensors? If bad or disconnected the computer will think temp is -40 and dump fuel into the engine. Although you passed an emissions test maybe the O2 sensor could still be bad. Try running with the O2 sensor unplugged for a tankful and see what MPG you get.

(https://birtydastards.com/frm/proxy.php?request=http%3A%2F%2Ffarm5.staticflickr.com%2F4017%2F4390712792_4a2867313d.jpg&hash=27a61d9f07d5a025366400941b3926c0b5022ca0)

And another thought... Is the speedo gear correct for the gear/tyre size combo you're running?

Title: Re: 11 mpg XJ Cherokee 4 litre 2001
Post by: Green Jeep on March 13, 2013, 10:01:17 PM

Many thanks, that is good info, I'll try that...

Running stock size tyres... thanks again Maf

Title: Re: 11 mpg XJ Cherokee 4 litre 2001
Post by: Brynjaminjones on March 14, 2013, 02:06:24 AM

http://ecomodder.com/forum/showthread.php/jeep-cherokee-aeromods-2614.html (http://ecomodder.com/forum/showthread.php/jeep-cherokee-aeromods-2614.html)  :hysterical: :hysterical:

Title: Re: 11 mpg XJ Cherokee 4 litre 2001
Post by: Lukemagnum on March 14, 2013, 08:02:13 PM

Does he really think that will improve the MPG?

Apart from the risk of overheating, blocking off the grille will probably make the cooling fan work harder, whether it's electric or viscous it still uses power which ultimately comes from the petrol.

Back to the original subject, being a 2001 petrol, it will be OBD 2 compliant. Put an OBD scanner on it, this will show all the engine sensor readings and give you instantaneous MPG, get someone to drive it at various steady speeds while you check the readings, these are precise readings as it works it out from the opening times of the injectors.

If you haven't got a scanner, buy one from eBay or Amazon for about £15 - that's about 30 miles worth in your case!

Title: Re: 11 mpg XJ Cherokee 4 litre 2001
Post by: Green Jeep on March 14, 2013, 09:14:41 PM

Big thanks will check and report, cheers Maf