SO today I'm driving a 300 mile round trip. Now I usually get about 17 mpg city/highway. So I get going and going down the road im getting really bad mileage. Using my scanguage II i usually get about 17-19 mpg at about 60MPH. Today I look down and my speedo says 70 and im getting about 23-24mpg. Now my scanguage is very accurate to what I hand calculate, and for the whole first half of the trip, I averages 25mpg going about 70mph at 1800-1900 rpms. AWESOME! My EGTs were about 200 degrees lower then they normally run and the truck drove great!

Now the bad news,

On the way back I notice that my EGTs are 200 degrees hotter then they previously were and my MPG's DROPPED dramatically like to 12-12mpg at the same speed and rpms....***? Also, for while if I hit a red light, it would do the infamous 3-4th gear torque converter lock/unlock, but it did this IN ALL GEARS? Also, I pulled over to check out the engine bay and I noticed that oil is leaking from the oil cap where you fill it up and oil was on the underside of the hood? Now the TQ converter lockup thing finally went away but according to my scanguage, I only averaged 15.6 MPG on the return home.

***? What is going on with the truck?

Please help,
Jeff

BTW - 2000 Dodge 2500 Sport Cummins 24 Valve, 4x4, Auto, Quad Cab, Short Bed With BHAF, Airdog 100, Edge Juice with Attitude, 5" Exhaust

 

MAP sensor???????

 

Just cleaned 500 miles ago....

 

When was last time tranny was serviced? A girlfriend of mine had problems and it turned out the fluid was so dirty it had filter plugged and started pumping fluid out places. But it was tranny fluid and oil.

 

Tranny fluid is clean and changed about 16k ago.

 

how is your crankcase venting? i would think you'd have to have pressure in the crankcase cavity to cause oil to blow out of the fill tube... any water in the oil or vice versa?

 

no water in oil, and how do i check crankcase venting?

 

cleaning will do nothing for a bad MAP sensor!

 

How would I tell if it is bad?

 

bump
thinking it might be the map sensor but how do i check if its bad?

 

Just replace it.

 

Thats quite an expensive part to just replace without diagnosing (115.00$ i think)....

 

It costs $$$ to keep these things running. Parts only last so long.

 

Downhill on the way out, uphill same road on the way back?..

 

I've narowed it down to the MAP sensor.......using the scanguage and edge, what would the MAP sensor read? At id;e, im reading 16.5-17.0...should't it read in the mid 20's? Or could the edge be throwing off the map sensor reading?