All of a sudden I went from 18 mpg to 10. It's a 99 ram 1500 with the 5.9. Had problems with the tranny but all should be good. New plugs, wires, cap, rotor , alternator and injectors. Still get a misfire code on number 5. At a loss...

 

Checked the plenum? Read the plenum sticky??

 

I doubt you were ever really at 18 mpg.

But that's not helpful.


Have you checked the plenum like he said?

 

On my drive from nv to wisconsin I averaged out 17.7 mpg and you are right once I was city driving it dropped to 14-15. Will check into the plenum.

 

ya I got 18.7 once out of the old turd bucket running 75/80mph but she was tuned up and running like a top

you can test your injectors with a volt meter see if they are "working" correct but you can tell if they have build up

tire psi

brake drag

plenum

cat getting pluged up

death flash!!!

 

I got ~19mpg out of mine when new, but now feel lucky at ~15mpg.
But, I get ~15mpg regardless of city or hwy.

 

Wow the plenum is done in and it would seem it did in my front o2. Thanks for all the input and the video is great on plenum replacement. Just waiting on my new parts from Hughes.

 

Test the cat as well. They also tend to be victims of a blown plenum.