Problems with early 99
 

Hi im new to the forum, I am in automotive school and has been aquiring alot of knowledge about these 7.3s since i bought mine. Heres what I'm dealing with. Poor fuel economy, loud injectors, runs rough when hot. codes : P1668 PCM -IDM Diagnostic Communication Error and P1280 Icp low circuit. Truck has new single shot remans, dp tuner, diy intake, ccv mod, frx, and turbo back exhaust. Starts right up every time and hasnt stalled on me yet. It did however stall after I did a test for oil aeration that calls to hold rpms at 3300 for 3 mins. When I let off the throttle it stalled right out. When hot rpm at idle and returning to idle becomes irratic sometimes and dips down and then back up. Buzz test fires all injectors and only sometimes give me the P1668. Installed a new fuel pump today which brought back some horses but still has the same issues. Any help would be greatly apreciated, thank you.

Need to know what the ICP is reading before anything else. Could be a bad IPR or HPOP.

ICP and ipr duty cycle seemed to be in acceptable ranges. Id get another reading but I pulled the pcm and idm today. Cracked open the IDM and it was dry and clean however the posts that come off the diodes on the middle block are loose and able to touch each other. Im assuming this is a problem.