I have RV with a with a 7.4L engine that is giving me a 14 and 34 code. I looked the codes up and I replaced the coolant temp sensor and the IAC but I am still getting the same codes and the engine has no power, sputters and back fires when trying to get going from a stop. It also doesn't want to stay running when cold and today after a test drive it stalled pulling it back in to it parking spot. I hope someone can help me figure this out.

 

Have you looked for an intake air leak, as in a split or cracked intake hose/line?

 

I checked all the vacuum hoses to the carburetor and to the intake manifold and they all look good. I then started the motor kept it running and sprayed them with carb cleaner and there was no change in the way the motor rent. Could could it be the throttle position sensor ?

 

I just replaced the leads to the coolant temperature sensor and that seems to have resolved the issue of running rough when cold and not staying running when cold. Took it out for a test drive still bogs off the line and backfires when you try to give it gas from a stop. Once you get up and going seems to run decent but still lacks power.