Hello, I have a 2000 excursion with a 7.3l, 4" exhaust with 6"tip, k&n air filter. I recently turned over 200000 miles and I have noticed my fuel milage going down. I used to get 15 pretty much no matter what except when I towed my 34' toyhauler and it would go down to 10. Now I get 12 and 8. I faithfully change the oil (even the top 3 quarts) and the fuel filter. I put in fuel aid every service also. Is there anything I can do to get it back? I was also reading that it is a good idea to flush the motor, but I don't know what to use on a diesel? Someone mentioned the napa engine flush is good. if so do you use only 1 can or more because of the oil capacity?

 

At 200k i would be more concerned about boost leaks, exhaust leaks than flushing the oil system.
Exhaust back pressure sensor tube cleanout procedure might be all thats needed.

Got gauges?

Very important tidbits of information when tracking down power loss are:

Fuel pressure
Icp
Boost
Engine oil level/type


Check for exhaust leaks at the up pipes to collector connection.
Check the turbine side of the turbo for soot.
Check around where the exhaust manifolds mare to the heads for soot.
If you see soot... you have an exhaust leak.

Search : boost leak detector cap

 

Boost leaks and injector age are common culprits at that mileage. I will say though, I am still running factory sticks and I get 10 mpg towing the 5th wheel and 19 mpg empty highway without cetane boost. My numbers go up a couple points with cetane boost.

 

no, I only have stock gauages. The exhaust looks good, I don't see any soot around any where. Is there another way I can test for leaks? I have also cleaned that tube several times during maintance.

 

We're assuming your fuel and air filters are in good shape. The drop in K&N has a reputation of not being good to diesels with a turbo, but some have had luck with them. If you remove the oil fill cap with the engine running, is there any pressure coming out the fill tube?

When exhaust leaks were mentioned, it was in reference to the up pipes where it connects to the back side of the turbo, not the actual exhaust pipe that comes off the side of the turbo and exits out the rear of the vehicle. Soot stains on the firewall at the back of the turbo or on the up pipes is what you want to look for.

For boost leaks, when was the last time you checked the hose clamps on the 6 rubber boots on the CAC tubes and turbo manifold?

 

If everything mentioned checks out, you might have a bad sensor or 2.... or so

 

okay. I did a boost leak test everything is good. It had a small leak on one of the rubber hoses and I just tightened up the clamp and it fixed that. I had never heard that with a k&n filter, but I have been running it since I got it, do you have a different recommendation? How about a chip just to help the fuel mileage is that possible? What sensors should I be looking at?

 

I had a Superchips programmer on my F-150 that had a fuel economy setting. When I used it, i actually got worse mileage. My money is on a bad sensor.

 

Break out the chisel and the stone... I hereby declare this one thing as gospel (to date). The absolute best remedy for poor fuel economy is getting the truck back to 100% working condition. No chip or sauce will liven the party when the host has the flu.

To introduce myself, I almost never make such bold declarations, so I wouldn't post this lightly. I have multiple scan tools that look at every sensor on the truck, and I added some sensors of my own (dual EGTs and Fuel Pressure). I have tinkered with my truck with my Obsessive-Compulsive Disorder and monitored the results with my gauges. I have an all-time low of 15.5 MPG, an all-time high of 19.6 MPG, with a 16.5 MPG winter average and a 17.5 MPG summer average (empty). Other trucks have actually done better than "Stinky" has... so there is no reason you can't improve your economy.

With the economy you had before, you either drive short trips in town a lot, drive like a madman, or your Ex has been ailing a while.

Cleaning the tube and the sensor is a good practice, but you have no way to know if it has truly solved the Exhaust Back Pressure sensor reading - not without a scan tool or scan gauge. I cleaned mine, then checked the reading - no improvement. My sensor had what is called a "bias", which means it already had a false reading before I started the engine... so it had to be replaced.

You need to know what your boost is (for example), so you can install a boost gauge, or "tap in" to the boost gauge that's already on the truck - again, a scan tool or a scan gauge. The scan tool/gauge gives you access to many very expensive sensors already installed in the truck, plus you can see what the "brains" are doing with those sensor readings (how it controls the engine and transmission).

Are there any mods to the engine, other than the big-breathing exhaust and a gasping intake?