both were changed with new NTK units, and they are functioning correctly

 

Hmm is the exhaust original , cat etc?

 

The piping and cat and muffler appear to be, the header does appear to have been replaced at some point.

To be honest it isn't in bad shape for a 99 original. The muffler has one spot on it that's starting to get rusty but hasn't developed a hole yet. I do plan on going with a new cat and muffler but other things are more pressing… like a lift that's sitting in boxes right now!

 

Do yourself a favor and purchase a scan gauge or ultra gauge (about $70)...then you can see what flow rate you are at live time when cruising at 65 mph. A properly running engine can only take sooo much fuel before you see the affects of excessive fuel (soot tail pipe) gas in the oil, etc...

How are you monitoring MPGs and what is your commute like? average speeds, stop-n-go, short trips...

 

From home to work is about 7 miles, a couple stop lights but then cruising speed about 45-50 mph. Enough to get it into low gear. As far as the scfan gauge i already have one thats how i run diags and look at live data, Snap on Ethos scanner. I might try that though while driving to see what everything is looking like. good idea

 

It can't.

That's called, "People who don't understand the basics, grasping at straws and committing the classic logical fallacy of "post hoc, ergo propter hoc".


Nor is a 10% ethanol blend going to make any noticeable difference. That's all we have around here, and I get in the 18-19 range.

 

I agree with you about the post on the motor mounts.

 

Hmmm. Do you mean, high gear? Low gear is 1st. That's where you start out from a stop.


How are you calculating your fuel economy? Where are you getting the 11 MPG number?

I'm asking because something is wrong here. If you have a condition that is causing your engine to suck down that much fuel, you will see it in the exhaust, in your oil, everywhere. It will be obvious that you are running way too rich.


One other thought - 7 miles isn't enough to get the engine & exhaust system completely warmed up. Mileage aside, that's very hard on a vehicle. You should make sure you get it run for at least half an hour every few days to burn the moisture out of the system.

 

Depends on the vehicle. Personally, I have seen from a 10% drop with E10 (96 Intrepid 3.5) to no measureable difference (06 Liberty 3.7).

 

Ethanol contains less energy than gasoline, so ethanol blends get fewer miles to the gallon.

Ethanol advocates contend the drop is 2 percent or less for E10, but large scale studies don’t prove that to be true.

Iowa State University, after reviewing independent studies using fleet vehicles, estimates that E10 delivers 96.4 percent of the miles per gallon of gasoline, a drop of 3.6 percent.

3-4% reduction in gas mileage in the 4.0 is accurate from research I have studied, and from my personal numbers.

 

Like bad motor mounts, 3.6% is a long way from explaining 11 MPG.

So far, in fact, that it shouldn't even be mentioned. It does not even BEGIN to explain that kind of mileage. If somebody says he's getting 15 or 16 and wants to improve it, the ethanol factor sure has a place in the discussion.

But not with 11 MPG.

He's got major problems with vehicle or his measurement methods.

 

Well I can tell you this, no gas in the oil or coming out of the tailpipe. Only thing out if the tailpipe is condensation. I definately know the signs of this dealing with a renix that was running super rich for a long time. Gas pouring from the exhaust. I calculate my mileage like most other people, miles driven divided by gallons put in at fill up. Now I didn't get into my complete daily routine but I can if you think it's relevant. I do a fair amount of driving around running errands and things after work also so the vehicle gets used; we primarily take mine when we go places to keep the mileage down on the 98.

Your right about the low gear and high gear. Words were twisted.

I just filled it yesterday and was at 12.2 on the mileage so up a little but I did do more 55+speeds on that last tank. We will see in a few days what the difference may be.

 

Do you have a overhead console?

 

About the same as I get with my '96- mostly city driving. Your year was rated at 14 MPG city when new, and the EPA numbers back then were a bit optimistic, IMHO.
http://www.fueleconomy.gov/feg/bymod...Cherokee.shtml
I'm not entirely convinced you have a huge problem. Perhaps a minor one.
Relatively short trips, cold weather....
you aren't letting it idle to heat up, are you?

Your tire size is causing the odometer to read 2% low, that's about 1/4 of one MPG.

 

It does warm up for roughly a minute, just enough to get the juices flowing!