engine power sporatic under power??
Hi all. new guy to the forum here. I have been reading everything I can to figure out my trucks issues to no avail. I have a 2000 F250 cc, AT. I have a DP tuner and 4" (?) exhaust. I started having issues a couple weeks ago when my truck suddenly failed to start, but would crank fine. I replaced the cps, and glow plug relay to try to remedy the no start. didn't work. I towed it to the body shop that I work at and had our mechanic diagnose the problem. finally come to the conclusion after the scanner having no communication with the ecm that it was a bad connection with the tuner to the ecm. retaped the tuner to the circuit board and everything was good.....for a couple days..... then it failed to start again. so I pulled the ecm, re-secured the connection and I was off again.....for about five more days, then it failed to start again!! this time I took the tuner all the way out and just drove the truck with the stock settings in the ecm. but driving it this way I noticed that it periodically ran normal, then like a switch was flipped it would be very underpowered, would not build boost past about 5-7lbs and the exhaust temp would only go to about 800. Holding full throttle it would maintain this low power condition for varying lengths of time, then like a light switch again it would accellerate like normal. and this on again, off again condition persists still.
Yesterday I put the tuner back on after making sure to clean the connections very well to try it again and see if my problems would go away or persist. with the tuner on setting no. 1 (stock), 2 (+40 hp), and no 3 (80 hp tow) the surging problem persists. with the tuner on no 4 (120 hp) I cannot determine if the surging is still there or if it is "overriding" the problem by dumping more fuel to the engine. any help would be greatly appreciated!! thank you.
Also a scanner indicated codes p0591 and p0476