The dragon bit me.

[Dubzilla]

I recently took a vacation to the Great Smoky Mountains National Park, and, of course, I -had- to drive the dragon at least once.

It went well, but afterwards I decided to travel back following a different route.

As I was headed uphill, my car started bucking and losing power, eventually it slowed and bogged a lot. I drifted back down the hill into robinsville, ate lunch, came back out, and headed another direction, with the same result. Came back again, my girlfriend called AAA. Got towed, some guy who owns his own shop replaced the fuel filter, all the shops/dealers/whatever were closed so that was the only thing I could even try.

After all that, I headed up 441 which runs through the middle of the park, but has to go over the mountains, so sure enough, after awhile, near the top, it started doing it again. Stopped, let the rain pass cause it was bad, went again and it wasn't as bad, but thankfully i got over the hill and was able to drift in neutral all the way down.

The guy who did the fuel filter got this code (flashed for a split second on the way to NC, turned off immediately and no problems the rest of the way until after the dragon run):

P0300 - Random Misfire The random misfire DTC indicates multiple cylinders are misfiring or the PCM cannot identify which cylinder is misfiring. Camshaft position sensor (CMP)
Low fuel: less than 1/8 tank
Stuck open EGR valve
Blocked EGR passages
One or more EGR passages may be blocked or partially blocked. If this is the case the Misfire Detection Monitor will indicate the EGR port to check for possible blockage.

I was sort of hoping it was an altitude problem, and the car got us back to MD, but with slight misfire off and on the whole time.

I changed the plugs, wires, and air filter cause it needed it anyway.
The cylinder #1 plug was rather black and smelled of fuel, the others didn't but the little prong that sticks out of the white part (I have no idea what you call it) is completely worn down. On the cylinder 1 plug it looks to be about 1/8th of an inch.

After driving today for 3.5 hours, the misfire started again and i had to pull over. I think it stalled after i put it in park, but I can't be sure because i was starting to turn the key off. After sitting for about 5 minutes, it started and I drove it home (about 1.5 miles). I checked a bunch of the EGR stuff today, unplugging and plugging, but to no avail. After reading the DPFE stuff, I think it could be the problem, but I doubt that simply the DPFE would make it misfire badly enough that it wont run well enough to drive.

What's even more frustrating is that I can't replicate the problem readily, so troubleshooting with the car running fine is pointless.

I was thinking coil, alternator, or fuel pump, with problems relating to heat from running a long time or heat soak from the engine.

Then again, it could be a million other things.
So basically, I'm trying to figure out a way to troubleshoot without just throwing parts at it. I have to drive for long periods of time on a regular basis, so downtime because of car troubles is really bad for me. Thank you for reading all of that and in advance for any advice.

edit: longest post ever, i know, but i felt i should be thorough.

[Dubzilla]

Also, I have had this problem once before, a year ago on my way to a DMB concert stuck in traffic on a hot day. Identical symptoms and conditions. (hot, engine under load, after driving for hours on end.)

I had the transmission flushed and it was fine until now, so I don't know if the flush helped or if it was another cause that didn't show up again for a long time.

I believe the two incidents to be completely independent of one another.

[G-forces]

You should clean it out on the inside as good as possible first. Run a couple of cans of B-12, or Sea Foam, one through the gas tank and one through a vacuum port. Try to clean the valves that way.

Put a quart of oil flush in (the thin stuff, basically kerosene) and drain the oil. Put in Marvel Mystery oil 1/2 quart to 4 quarts dyno oil when you refill (if you run synthetic, forget about the Marvel). And I'd go ahead and change the spark plug wires with the plugs right now.

Then do the EGR hack and see how it goes.

[TXFO]

probablly the coil.

maybe bad gas.

[Dubzilla]

Thanks, I doubt it was bad gas, cause it did it at home, seafoam and the coil was my next step, so here's hoping.

[MichaelXi]

The DPFE Sensor is plagued by water.
Did it start stumbling AFTER the rain Started?

[Dubzilla]

Nah, it was really dry and hot actually.
I've got a few more experiments to do, hopefully i'll have it licked by saturday.

[drjkel]

Be aware that the transmountain road (441) and the Dragon have a venerable history (at least 50 years now) of causing vapor-lock problems, especially in vehicles with weak fuel pumps under high-ambient temperature conditions at moderate altitude. Modern high-pressure fuel injection systems are rarely susceptible to vapor lock, but it still happens. Typically a super-heated power steering line affects a nearby fuel line. I haven't specifically heard of this happening in a Focus, but it has happened in many other cars. It's usually diagnosed by pouring cold water on the engine-compartment fuel lines at the time of the problem.

I'm surprised the outfit in Robbinsville didn't know about this. I'm sure Milsap's would have. Also, Mountain Ford in Bryson City has experience with this.

Probably not your problem based on your other symptoms but something to be aware of.