2011 LR4 - MPG getting worst

[stufrowin]

One of my throttle body bolts was loose and subsequently I think the gasket/o ring had a little leak, after replacement idle smoothed out. Not sure how an air leak would affect the long term vs short term etc.

 

[ktm525]

I would revisit the tires and fuel.

The 22" wheel/tire combo has shortened your gearing 2.5% . Add in a less fuel efficient tread pattern and construction (I am going to stretch and say 5% over a good highway tire like a Michelin Latitude or eq). This could account for a 7.5% reduction in fuel economy. It may knock you down about 1.5-2.0 mpgs.


2) What type of fuel are you using? I am at some altitude (4000') and run 91 octane. I see a mileage drop if I use lower octane. Also I use a fuel with no ethanol blend, just dead dinosaurs. Any blended gasoline drops the mileage. Are they running special California witches brew for fuels?

 

[djkaosone]

@ktm525 I've had the 255/55r19 Goodyear Duratrac on before these issues started to occur. In matter of fact, I was averaging well above 16 mpg and getting around 20 mpg at best. I don't believe the the tires are at fault. I rotate them and fill them with nitro air at least every season, except when I have to air down and fill with regular air from a Viair 400P.

I should also mention that I had the rig flash "Restricted Performance Warning" on 3 separate occasions without any codes. Once during a normal day on a uphill freeway climb, once at night on a flat freeway, and once going downhill at night on surface streets. As soon as I pull over and stopped the car for 10 seconds, restarted, and all is normal (no codes). Since the first time, I keep my i930 code reader in the rig.

 

[ktm525]

OK just looking for causes. I imagine your fuel has remained the same before and during this mileage loss? Perhaps your station switched recipes on you lol.

 

[djkaosone]

I just ran a live data stream while driving it and let me know if this is normal.

Its about 100*F out... rig is warmed up. Just looking at the Calculated LOAD value I get the following.

Parked: 63-78%
Parked with AC on low: 20-25%
Driving under 40 mph: 60-100%
Driving under 40 mph w/AC: 36-85%
Stopped on D w/brakes w/ and w/o AC: 100%

Either way, all these numbers seem way to high. Hopefully that helps someone help me.

 

[jhartz]

What I would like to see is how fixing the loose throttle body effected your fuel trims. Frankly, I think you have fixed your problem.

 

[stufrowin]

What I would like to see is how fixing the loose throttle body effected your fuel trims. Frankly, I think you have fixed your problem.

My thought was if air leak was significant enough the MAP sensor may get an innacurate read, and from my understanding the MAP, O2 sensors etc play a role in fuel trims. But yeah it was probably a long shot just sharing my experience.

 

[jhartz]

I think you meant MAF sensor. Did the long term fuel trims improve? Still no codes?