I have a 2003 CR. 5.9 3500 dodge. bought new and only added a K&N filter. It has only 88'000 miles and 80% empty truck miles. It has developed a rough idle when warmed up. It also lost MPG from 16 to 12. Mechanic diagnosed it was a bad injector or more cylender blance unable to tell which. I installed an airdog II 150 even though the stock pump tested fine. I then installed 6 new stock bosch injectors and fuel tubes. This truck runs exactly as it did before rough idle when warm and 12 mpg. Somone said the MPROP or fuel actuator on the pump bought one for $106 still runs the same. I am running out of money and patience on guessing. Now mechanic says he thinks it may be a flat lobe on the cam or bad valve. Please dont mention compression test. seems very expensive to remove each inj. fuel tube ex. rocker etc. to get a low cylyner which coud be eather a flat lobe or head issue anyway. I hear some stick shift trucks have there flywheel come apart. I wonder if my torqconverter could cause it. There is no codes and truck runs fine. Tiny amount of smoke and no there is no fuel in the oil. The rough idle stops with just a tiny amount of fuel like turning on the ac or putting it in gear. any other guesers.

 

How bad is the idle? Does the rpms fluctuate heaps?

 

Check the harmonic balancer. The rubber should have no splits and the timing marks should be aligned.

You could also read the tempeture of each exhaust port with a non-contact thermometer. This might show if there is a weak cylinder.

 

Get some Howes meaner Cleaner. Dump the amount the label says into the tank. When mine did that, that's what I did and it made a world of difference. Took jut a few miles driving to feel it get better.

 

The rough idle is not bad enough to see a fluctuation on the in dash gauge but it does show on the snapon scope just slightly. I am leaning towards a tourq converter or the balancer but both are expensive guesses. Unfrotunately my cheap ir temp tool has too wide of a beam and is usless. I even suspect the cat. could be plugged another guess **** I hate this game. I love this truck I am a dodge man to the end....

 

My rough idle went away with some Howes. A possible $10 fix would be worth trying first.

 

I agree not sure what Howes is I assume it is an additive I regularly use additives since here in California we have only low sulfer diesel and an additive is req. to lube the pump.

 

http://www.howeslube.com/meanerpowerkleaner.php

 

Did you figure it out , I could use some direction