I've been blindly troubleshooting a rough idle, hesitation and what is apprently an intermittent misfire. A few months ago, dealer replaced all plugs, 7 coils (one was fairly new and stress tested okay). When I unplug that coil, the engine will have a definite misfire. A few weeks ago, I replaced the alternator. Last night I replaced the EGR valve. My last trip to the dealer, they informed me the valve cover gaskets are leaking. The right side in particular and fills the plug well enough that it shorts the plug. Aside from what I think is generally impossible with the top of the cover leaking into a plug well, I pulled that coil and plug and it is dry, and I never smell burning oil either. The engine, aside from general greasy buildup (truck has 168,000 miles) looks really good, there is no evidence of recent oil leakage anywhere. On the exhaust side (before the EGR pipe orrifice) the DPFE hose was split open, the nipple was cracked and the hose was charred where the split was. I pulled the pipe and verify there are no blockages. I will be going down to parts store to pick up the DPFE and EGR position (assuming this is correct name) sensors. Last night, I was testing the DPFE sensor and EVR according to what the Haynes manual said. The EVR has 50 ohms which is within the specified 30 to 70. The DPFE has 5.0 volts reference, and when running shows 0.8 to 1.2 volts at the signal wire. The manual says it should go up to between 4 and 6 volts when it warms up, it never gets higher than 1.2 volts. So, should I go ahead and just replace the DPFE sensor???

Before I replaced the EGR valve and replaced the DPFE hoses, I had a P0405 (EGR Sensor A Circuit Low). I cleared that code. Drove about five miles today and hasn't come back on.

2002 F-150, Lariat, 4X4, Supercrew 5.4L, Automatic, 168,000 miles.