Not on a long trip, but adding another data point: 06 LX, bought it with 166k on the click last year, mall cruiser with full dealer service (*everything*, bearing repacks, prop shaft lubes, fluid flushes, by the book). Plugs were done at 131k. Currently sitting at 177k. Just got back from a 5k cross country drive. Went trailing in Hemet/Idyllwild 2 weeks ago, start with just over ⅔ tank of fuel (always top tier 91 octane), ran fine. Nothing technical, just fire roads, lots of climbing (H range, usually around 2200rpm in D, 5-10mph), outside temps in the 60s. Started from HWY 74, ended up on HWY 238, nice wide turnout/overlook area, so I stopped to take photos. All gauges read normal, no weird sounds or smells, fuel gauge reads a smidge under ½ tank.
Heard car stumble, thought that's odd. Then I hear idle dip again, so I ran back to car, gave it some throttle. It's running rough, like it wants to die, and despite throttle, comes down from 3k to 600 and stalls. Cranks strong, crank-hold is keeping it going, but won't start, so I switch it off. Scan OBDII: lean banks 1 and 2, misfire cyl 4. I chalk it up to the stall/lack of start. I did smell fuel, like a car running rich. Under-hood smelled normal. I let it sit for a few minutes. Cranks, starts, dies. Fortunately I had just made it to the highway and had enough cell signal to call for help. Half hour later, cranks starts, runs fine, so I let it idle, rev it a bit, just to see if it's stable. Few minutes later, dies again.
I initially thought fuel pump (BMW E46 previous car, similar symptoms with about as many miles, was fuel pump). No way I'm risking a mountain pass descent from 6000' or so with an unstable engine, so just wait for a tow home (2000'). Starts just fine. Drove it 50 miles to RPM Garage in Monrovia the next day, ran just fine. (Bro followed me in his LX, said brown smoke on hard throttle, could be because ran a bottle of Redline SI-1 in the tank). Steve at the shop drove it for a week, no issues.
Given what I know now, thought was bad fuel (bro with 03 LX did same cross country trip, suspected bad batch of fuel at one stop, had stumble issues whole tank, never returned), and bumpy trails dislodging crud and clogging fuel filter. FF was cheap to replace, so had that done. Fuel coming out of the filter onto white cardboard was gray/brown like dirty dishwater, tech said it shouldn't be that color. He blew it out, said not much restriction, so we're not sure what the issue was. I've been spooked and still drive scared, and don't want to venture too far out from cell range. (I broke all three of my rules this trip: never trail solo, esp new trail, never go w/o radio, and never go w/o telling someone where you're going).
