CM 871 getting 3.6 MPG

[Rawze]

Things someone can do to help eliminate fuel mileage problems after doing the normal stuffs...

* Replacing the Exhaust gas pressure sensor if it is more than 400k miles old, and ensuring its feed-line/circuit is not plugged up (this is common).

* Emnsuring the Altitude (Ambient pressure) sensor is reading correctly.

* Pressurize the entire engine with 30 psi of air using block-plates at both ends of the turbocharger. Check for boost, egr, and exhaust manifold leaks. You would be surprised the unusual places you can loose boost and fuel mileage, not just in the CAC.

* Check to ensure the Doser injector is not bleeding fuel all the time because it is leaky. Remove the Doser-pipe off the back of the turbo and crank the truck. See if the injector tip os getting wet with fuel. - Clean the tip well while your at it.

* Fuel line leaks that are hard to find. - Look for wet, oily spots under the truck or places that accumulate a lot of extra dirt on them.

* Adjust the overhead valves properly, inspect the cams to ensure they are not chewed up, and then perform an injector leak test. Leaky injector or out of adjustment valves cause all sorts of issues as well as can be fuel mileage problems.

* check the metering and fueling actuators so ensure they are not worn out. ref: http://rawze.com/forums/showthread.php?t...619#pid619


* ENSURE YOU HAVE THE RIGHT PROGRAM FOR THE WHOLE TRUCK and not just the engine. If someone changed the HP settings using a different program in the engine, this can be a big problem.

* Check for a slipped valve or injector cam ... may have bad cam sensor or crank position sensor, and all sorts of other places to look too.

* Wrong injectors installed into the engine vs the programming. Seen that too.

* verify the fuel mileage in the dash vs. what is measured at the pump. - if they are way off, then the fuel is not being accounted for in the ecm and this is bad. .. it has to be going somewhere if not onto the cylinders or Doser injector.

* turbo out of calibration or packed with soot.

* Intake or CAC restrictions or an aftermarket CAC or EGR cooler unit has been installed onto the truck... Doing Either of these are terrible choices.


maybe others can chime in as well.