12.7 Detroit DDEC 4

Air filters, fuel quality, or check mufflers for restriction? Did anyone mess with the programing? Like update with a lo nox program? Any gear change or tire size change?

 

All new filters. Truck has good fuel and 7 inch straights so no muffler restriction at all. Also no tuning has been done. No gearing or tire change either

 

My mechanic said next step is a tune from @rebel127. Truck is at Virdell diesel

 

Has the fuel pressure check/ regulator been checked?
Are the ecm power wires in good shape, (no cuts, corrosion, no crimp connectors, good clean copper)?
If all that’s good, have your bull gear checked, out of the 15 ‘01 model Freightliner’s with Detroit’s we used to have, the units with “great power” were the 6 that had the bull gear replaced.

 

I think you better get a new mechanic. 900 with an empty trailer is hot for a 12.7. You need to find the cause of that before you have it tuned. It sounds to me like its starving for air or is getting air in the fuel.

If it were me I would clear my head and start all over with my diagnoses process like I was looking at it for the first time. You missed something somewhere

 

I agree it's too hot. Just confusing because I know it's getting air and it has to be getting fuel to be running that hot. I have checked the fuel pressure but have not replaced the regulator. I will check for air in fuel tomorrow and have the bull gear checked
I was told to replace the barometric pressure sensor but I have not been able to find it or figure out how this truck reads barometric pressure. Yesterday the ECM was showing 14 on the barometric pressure but it was 31 according to the weather station here

 

Here is something that might help you (PDF format). This is for my 2003 Columbia which has come handy many times. Sounds to me like you may have an EGR valve leaking/hung open a bit. Barometric Pressure sensor will resemble a flash drive. Remove Venturi tube and check for carbon build-up.

 

The 2000 model DDEC IV is a pre emissions no egr motor. I found the barometric sensor. It's inside the ECM on this truck. Thank you for the replies

 

I have a similar issue with my 14L S60. It drives perfect but only chokes after a big downhill followed by a uphill. It starts to sputter and smoke up till it clears out than goes back to normal. It's happening when I pass the governed speed while on the downhill...

 

Take the governor off