Better MPG.... Ran out of things to check

[Glyphic]

Leigh Sells a FPR regulator doesnt he?

 

[Talyn]

Not for the return-less fuel system

 

[CASEY-R]

Other thing I wanted to mention is that O2 sensors can create piss-poor fuel economy without throwing codes. When a code is thrown, it is "bad-bad". It can be "bad" without throwing a code, though. Ask me how I know.

Was your problem with the pre-cat sensor or the after cat sensor? I'm getting 13 mpg average with the same build as the op so I did a full tune up and a pre-cat sensor with no change. The only extra's i've got in the jeep are a spare tire and some spare parts and tools.

 

[yossarian19]

My problem was the pre-cat sensor. Post-cat is strictly for emissions, to detect the amounts of o2 before & after catalyst. Engines run off the pre-cat 02 / afr sensors.
I also had problems with a rattly / plugged up cat before I put in the magnaflow.

13 mpg on winter gas and your defroster running constantly - thats about right, if it is mostly city mileage. Shameful but true - there might not be anything wrong with your rig. Check / clean your coolant temperature sensor connector for the hell of it, though.

 

[CASEY-R]

Thanks for the help. The cat was replaced about a year ago.
Still not convinced there's nothing wrong. I was getting 15+ last winter with mostly city. Highway mpg's are just over 14 now.

Sent from my VM670 using Tapatalk

 

[ScottH82]

Some good info, thanks.

What for o2 sensors should I get? So many companies make a replacement. I think I read somewhere that OEM ones are marked up (price) NTK sensors, is that true? And if it is should I just get the NTK ones?

Thanks

 

[XJCasper]

From my experience, I would stick with the Bosch factory replacement. Get them at any AutoZone or wherever. They will offer you a a hardwire cheaper replacement. Would not fit in my O2 bung.

 

[hubs97xj]

NTK from RockAuto.

 

[yossarian19]

xWhatever. NTK or Bosch. I'd go NTK because yes, I think NTK made them for Jeep.

 

[CASEY-R]

I got a new Bosch off ebay for $25 shipped.

That was the pre cat sensor. After cat sensors are twice as much.

 

[grainofsalt]

Wow, And I thought that going from 21mpg stock to 18.5mpg with 3" and 30's was bad...

 

[cameron770]

Any idea how to monitor this on a renix? I have a 180* stat that according to the gauge runs ~200* but would like to make sure it's correct and not lower. Currently getting 14-15 around town driving like I stole it so not too concerned.

Wow 14-15 around town..

I'm a renix 87 wagoneer... Automatic I get 11-13 town average around 11. Highway I get like 16. And I baby it. Have 280k miles, rebuilt rearend, 235/75/15 tires.. terrible gas mileage I thought about removing my muffler and seeing if that helps.. (Its bad) lol.

 

[fattmann]

For the sake of number comparison, my setup:

'92 XJ, Stock 4.0l HO, 3.07gears, 5sp, 3" bastard pack lift, 31x10.5 Grabber AT2s, non-corrected speedo (even tho GPS says it's spot on...) with ~250K mi. I get 15mpg city, 17-18,mpg hwy. If the ambient temp is over 80*F for the duration of a whole tank, I will pull 16-17city, 18-19hwy, no joke.

I shift at or under 2000rpm regardless. I will have to try shifting at 2.5K, last time I did that for a whole tank I remember my mpg going down.


My brother has a 92, ~4.5" lift on 32s, auto, with about 225K mi. I don't think he gets much more than 12mpg city.

 

[sidewaysstarion]

If you have a scan tool, check to see what your fuel trims look like.

 

[markaboo929]

There seems to be a wide difference on vehicle MPG's.I do however think the 24# injectors are a bit much...for instance I am running 4.88 gears 35" BFG At NV3550 Trans,in 5th I am just at 3000 rpms @75 mph...I get 17-18 mpg on highway...constant on road trips.A mix of the 2 city/highway will give lower results.By the way I have a 2003 WJ 4.0 in it operating on Renix equipment..just the sensors.I have retained the stock returnless for the 03 WJ simply by using the WJ fuel filter which is a fuel regulator @ 49 psi filter combo unit.Using Volvo 19# injectors...same as Ford except WITH the slot to correctly locate the injector on the rail....Plus you will get better mileage from a manual trans,due to the fact YOU control when and what rpm to shift at and which gear will keep you at 2500 and up.I did see a post someone said about better milage in a lower gear on highway...keep that in mind.Smaller injectors higher rpm-CRUISE rpm.Try the mentioned sugestions and check results....