I swapped a 5.2 motor for a 5.9 both magnum. Had some issues with it running at first but now it won’t run well. It’s a struggle getting it up to 50 it surges and is sluggish. All my sensors are new hooked it up to an obd1 scanner and fixed a tps issue and a replaced the crankshaft sensor. I’ve read that the 5.2 pcm will run the 5.9 motor with a loss of power and fuel economy I do plan on getting a used one next week at the salvage yard but was wondering if anyone had any ideas on how to fix the loss of power, surges, and misfiring before I get it.

 

Is the check engine light on? Still getting the engine codes as before (24, 27, 37)?

 

the codes haven’t been cleared but I had a buddy come over with his obd1 scanner and we figured out I’m a dummy and put on the tps wrong. I forgot to see if he could clear the codes but I can unhook the battery in the morning and see if they’re off. It’s idling much better but isn’t driving well.

edit: I put more gas in it and it cleared up. Idk if it was driving it and the computer figured out where it needs to be or the fuel pump was overheating or just sucking air. I do not have 4th gear though. I’d replaced the tcc solenoid to try and get rid of the code 37 but it never went away. I had 4th gear when it initially broke down so not sure what’s going on there.