2000 Dakota R/T bone stock 60,000 miles

I'm having some transmission problems on my truck and cant seem to get it quite right but now a new and worse problem has crept up on me...gas mileage!

I start the truck and at idle the electronic display reads 9 MPG and under very light acceleration (1200 to 1400 RPM) it sinks to 2 and 3 MPG. I checked the MAP sensor per the Haynes Manual and with the engine not running I get 4.5 volts but when I start the engine and read the #2 pin I get 1.38 volts when the manual calls for 1.5 to 2.0 volts.

Do you think this is the problem? Should I be looking else where?

Just for reference the transmission problems were erratic shifts and redlining before it shifts in WOT.
(I did replace a faulty pressure regulator and sensor)

This truck has been rock solid for the 9+ years I've owned it but it's falling apart on me.

Thank you,
-Keith

kwalker@t2drafting.com

 

Have you done hand calculations to back up the mpg? A bad tranny will cause bad mpg.

 

The last two half tanks I put in it got me about 50 miles each...so I guess it's approximately 50 miles to 11 gallons so that averages out to 4.5 mpg. It was mostly at 10 to 15 mph as well. (been looking for a lost dog)

 

If it was actually running that stupid fat at such a low RPM, it wouldn't make RPM and would constantly try to die. A sensor somewhere has to be throwing all kinds of codes....Either O2's are showing a bad calibration or the PCM is shot. Even if all 8 injectors were hung wide open, the O2's would be screaming rich rich rich.

 

Have you checked for codes? Do the key-dance trick.

Starting with the key off, key on (not start), off, on, off, then leave on. Any codes should display in the odometer. Bad O2's will NOT always show a code and they can/do get lazy after a while. Your tailpipe must be pitch black.

 

Yeah that is majorly rich or something. I think monster trucks get that kinda mpg lol

 

No codes, that was the first thing I checked. Tail pipe looks normal. Not a hint of wanting to die. Engine runs as smoothly as day 1.

 

Umm well, what about a fuel rail or fuel line leak?

 

I think User can rule out that one (his truck burned to the ground because 1 injector O-ring failed)

 

I have a buddy that said since I changed the pressure reg and sensor I need to have a "quick learn" any insight on the procedure and if it pertains to my truck?