2004 4.6L V8 Mounty - 15MPG combined / Black Exhaust Tip | Ford Explorer Forums - Serious Explorations

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2004 4.6L V8 Mounty - 15MPG combined / Black Exhaust Tip

tmsoko

Well-Known Member
Joined
March 12, 2001
Messages
847
Reaction score
3
City, State
Plymouth, MI
Year, Model & Trim Level
2010 Adrenalin
OK, something has happened to my Mounty's fuel consumption. I have been getting 15MPG this summer combined. That is ~240miles per week highway at 75-80 and ~60 miles / week tooling around the streets. No aggressive / hard take offs, just normal driving. Also notice the exhaust tip is pretty black, running rich.

I have done a basic overhaul - fuel / air filters, plugs, engine / trans oil, belt. No change at all. Wondering on the black exhaust and its coordination with the poor economy. Thoughts are vacuum leak causing lean read at O2, then processor adjusting by dumping fuel? Another thought is O2 sensors or MAF sensor?

Before I just start willy nilly changing parts ($$$), wondered if there are any common causes / higher likely hood points to start??

Let me know the ideas!
 






Do you track and record your gas mileage mathematically, or by rough estimate (per tankful), how much was the drop in mileage (.2 mpg or 3 mpg), did it happen suddenly or rapidly, and did it happend before or after the your parts replacement? Did you notice if the exhuast tip was black before?

By use of the descriptor "basic overhaul" and the parts listed, I am concluding that the engine was not overhauled (no indication of that), but that you replaced the parts listed. Did you go with factory OEM plugs and how did the old ones look when you pulled them out (white, beige, grey, black, etc?)? Did you unhook the battery to reset the computer when you did this work?

Is your Check Engine Light on? Have you pulled any OBD-II codes?

Assuming you checked the tire pressure (#1 reason for poor mileage), and that there were no other changes to the truck (added large roof top carrier) I wold do the following:

If not tracking gas mileage mathematically, do so so that you can come up with hard data - makes it much easier to trend.

If you had this problem before changing the plugs, reading the plugs may be helpful.

Clean your MAF - be careful and do it right - very sensitive part.

Check for vacuum leaks, as you stated.

Replace the PCV valve.

Go from there.

(Hey, I just noticed that you and I joined the same month, and it took me over 8 years to get to 500 posts - you beat me)
 






First thing I would say is pull the codes and see what that comes up with.

And Rhino, it's ok to take that long for 500 posts. I have belonged almost as long as you and I thought it took me a long time to reach 1000 posts. But it's ok not being a post *****;)
 






And Rhino, it's ok to take that long for 500 posts. I have belonged almost as long as you and I thought it took me a long time to reach 1000 posts. But it's ok not being a post *****;)

I dunno, Dog, compared to me, you are a PH!!!;)
 






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