Dodge Repair: engine/transmission prob

Question
QUESTION: i am having drivability issues with my 2004 dodge 1500 quad cab slt. The truck has a 4.7 l engine with 153000 miles on it. i have just had the transmission rebuilt but the problem im having has occurred before and after the tranny was rebuilt. the engine on most day runs fine until i try to accelerate and then, by the way the truck is driving ,i can tell that it has just encountered an error. the engine is roaring just to gain any type of speed but no matter what i do the engine will not rev up past 2500 rpms. i can come to a stop and try to accelerate but the engine is roaring and will not go past 2500rpm. i have not gone over 60mph when this is happening. the strange thing is when this error has occurred i can park it and put the truck in park and the engine still will not rev past 2500rpm. i turn it off and come back most time i can rev the engine up to 5-6k no problem. i was told this model does not have a rev limiter. i have checked the codes and nothing has come back. my question is what is happening and what is causing it ? thank you in advance for help given.

ANSWER: Hi Arnoldo,
I am entertaining an out of town visitor until Sunday afternoon. I would prefer to respond on Sunday rather that give you a rushed response know. Look for it coming before the end of the day. Thanks for your understanding.
Roland

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QUESTION: Not a problem. Look forward hearing from you. Thanks again.

Answer
Hi Arnoldo,
When you say about the fault code check that "nothing has come back" do you see a definite response to your attempt in the odometer window of the cluster, or is there no change at all?
It may be that there is a problem with the fault code readout if no change. Do the "on-off-on-off-on and leave on" in 5 seconds or less. If no response then a fault code readout via the under-dash socket with a plug-in reader would be worthwhile. Often a nationwide parts store will do it for free (e.g. Autozone).
I can't think of any specific cause other than a vacuum line attached to the intake manifold being loose or cracked, so use the diagram for those lines that is on the underside of the hood to find them and check each one out. Any such leak can lean out the mixture that would behave as you describe the engine doing.
Let me know what you learn.
Roland