2006 scab 5.4L, 143k miles. Two weeks ago a bit after filling up with gas, I began to notice a rough idle. Truck idled at ~500 rpm per the dash gauge, which has been typical. A definite stumble. Also hard to start. It would crank and crank and then sputter starting.
Cleaned the throttle body, MAF, and replaced the fuel filter. I checked the state of the fuel pump driver module, but it was showing as being one already offset from the frame, so I chose not to swap it out. Truck fired up and all seemed well.
Then the rough idle and hard starting started again. Today I checked the codes and got back P0172 - bank 1 is too rich. There was a pending misfire code, too. This evening the CEL turned on - I checked the code again and it was P0172 thought the misfire code had gone away.
According the my Edge code reading, the fuel rail pressure was about 39 psi, with a desired fuel rail pressure of 56 psi. That's a pretty big gap, but I'm not sure I know what it means or if it's significant.
Spark plugs were done ~3k miles ago and I replaced the COPS at the same time - all are MC parts. Air filter is clean (need to get a replacement foam gasket).
Seems like there's a good chance I need to replace at least one bank 1 fuel injector, which means I may as well do all four. The build date is 02/06, so I suppose it's possible I have some of the old bad injectors I've read about that made there way into early 2006 models, but I don't really know. Maybe a fuel pump issue? The driver module? Maybe the gas I bought was bad for some reason? TPS? The lack of fuel pressure suggests either an injector is being kept open or leaking or the fuel pump isn't moving the fuel it should.
Any insights or recommendations are appreciated. I'm willing to throw some new injectors at the problem to see what happens and probably will unless someone points me in another direction.
I've owned the truck since last August and it's been good so far. The PO seemed to have taken care of it.