Mustang running rough

[Hmichelle20]

Hey guys, I drive a '98 mustang gt convertible, we swapped the motor out for an '03 v8. It has roughly 140,000 miles on the engine. In the past month it has started running real rough and my dad and I can't figure out the problem.
When I first crank it and drive it it will be okay for about 10 minutes and then out of nowhere it will start idling real rough and when I give it gas it will barely go anywhere but my RPMs go crazy like I'm giving it heck but I'm barely pushing on the gas. In order to get it to go I have to basically put the pedal to the floor (which is very hard to do in bumper to bumper traffic) and then it will like snap out of it and go for awhile until I get stuck at another red light and then it's a repeat. We've checked the coils they all seem fine, everything is hooked up correctly, it's not bad gas I've ran a whole tank out and gotten new, we're stumped.
Any suggestions would be great as this is my every day car and I don't have the money for a new car and won't for a while.

 

[wmburns]

but my RPMs go crazy like I'm giving it heck but I'm barely pushing on the gas.

Does this mean that the RPM's rise like the transmission is slipping?

Manual or automatic?

 

[Hmichelle20]

Does this mean that the RPM's rise like the transmission is slipping?

Manual or automatic?

Automatic. We actually found out it was a loose hose from the EVAP canister. The hose had dry rotted and come off. Got that fixed but it still idles rough mainly when my AC is on. If I cut the AC off it smooths out. I took it to autozone and the codes that came back were the evap, and my 02 sensors. Could that be causing the rough idle?

 

[wmburns]

<doing my best Johnny Carson Carnac the Magnificent>trouble shooting parts changing by guessing DTC codes?

In all seriousness there are 1,000's of DTC codes. Each has a story to tell. Why make us guess? Always post the full DTC codes if you want real help.

Is the AC low on Freon? Does the AC short cycle? The PCM maintains two IAC idle trim values. One with the AC on and the other with the AC off. IF the AC is low on Freon, this could prevent the AC from running long enough for the PCM to re-learn new AC on IAC idle trim values. Try jumping the AC low pressure switch to force the AC to run at full operating temperature for several minutes. Remove the jumper. Did that help?

What else have you done to rule out an intake vacuum leak?

Carnac the Magnificent
https://en.wikipedia.org/wiki/Carnac_the_Magnificent


View: https://www.youtube.com/watch?v=ZFQFf_Vb0Hw