Looking for some input.
Mileage is down to roughly 10.5. Used to be 16.9. This has been a progressive drop over about 3 years. Yesterday going to the lake (not towing anything) it seemed like something was literally holding it back. This isn't the first time I have encountered this. My first thought was the e brake was on so I checked it. My first though would be the brakes are dragging, but I'm not smelling them, nor are they wearing prematurely. Around town it seems to run really good. Lots of pep and seems to pull really nice through the rpm band in first. Last couple of years I've changed the fuel pump, filter, plugs, coils, checked sensor activities, and watched the fuel trims. Few weeks back I changed the primary o2 sensors because I have never changed them, and they looked pretty nasty when I pulled them.
Anyone have any ideas ?

 

Year... Engine and mileage ?

 

If your O2 sensors look nasty you got something going on.
Doesn't matter how old they are.

I changed my mine @ 240 k and they look good. Still work fine too.

Engine uses this to control the fuel....... need to see exhaust gas not be coated in crud

 

2000 4.6, auto, 4wd, super cab, 225000.

My definition of nasty is they definitely didn't look new. Had some redding from fuel additives. Was apparent they had been in there way longer than I've had the truck. Attempting to get the performance and mileage up was why I changed them as I new they were old. Even changed all the emission hoses under the bed when I changed the fuel pump.
There's time when I'm on the interstate and it just want to fly. Takes very little peddle to keep it at 70-80, then there's times it won't get out of it's own way.
No CEL.

 

Something you might want to consider is you live in Arizona. Arizona not only has the winter and summer blends of fuel, they also have 3 different geographic blends they call "Areas A. B and C." If you are crossing into different areas and buying fuel while there your PCM is going through a re-learn process which is hard on mileage and performance. This is no where near as bad with newer vehicles but with the age of our trucks, you can't help but notice the difference.

 

I'm actually in Arkansas. Arizona is AZ and I try and run only non ethanol fuel. I've been chasing the decrease for a while, but last time I checked it, it was around 15.

 

LOL. Well this is timely. I just put up a post about my ability to make stupid mistakes. Sorry Rod.

 

No biggie. We all make em.
Just went out for a test drive and to check o2 sensors. They seem to be functioning ok. IAT was good when I got back. There is definitely a mild to hard sputter going on, but I can't get my scan tool to get to the pid because the evap test won't complete. GRRRRRR. I have pulled a vacuum test on every component I can get to and everything looks sealed. What's weird to me is the exhaust smells clean. Every car I have ever owned it smelled like exhaust. Even our 06 Altima. Hopeing I don't have to rebuild the engine. That money is just not there.

 

Is it possible that the timing chains can be causing this ?

 

Rod,

Before tearing in to timing chains or anything that involved consider changing your fuel filter again. This time cut it open and see what's inside. I've only owned one diesel and went through a lot like what you're describing because of sand.