My explorer left me stranded this morning on the way home from work. It had been acting up a little before. I have a new fuel pump in it, so I can rule that out. Here is what has been happening:

Lately I have been getting poor gas mileage, and the pedal seems to have to be pushed farther down to go. I let the truck warm up this morning as usual, but when I got a little way down the road to stop at a stop sign, it died. I couldn't get it started. I let it sit for awhile. After about 40 minutes, it started after cranking it for a long time. It stumbled and ran rough for a bit and smoothed out!

This has happened before in the last couple of weeks. Where do I start looking for problems? I don't have a ton of money to just start replacing parts. I do have 145,000 miles on the truck, so I knew I would need to do something soon anyway. I also notice that sometimes it seems to idle high and erratically lately, but then it smooths out. Please offer any suggestions, I need this truck :) Thanks!

That sounds like the same behavior my mom's old bonneville had - replaced fuel pump & fuel filter cuz that seemed to be the problem, but replacing the airflow sensor in the intake tube fixed it.

to get it restarted. I had that problem after the fuel pump was replaced, it would stall at stop lights. Some of the springs are slightly off center in the FPR which causes the valve seat to wear only on one side. High vacuum conditions open the valve the most and it sticks open to one side. Found about a dozen people with the same experience. You might want to try monitoring fuel pump pressure or current to the pump (4-5A).

I just changed the fuel filter, cleaned the mass air sensor, and IAS? Anyway, I am pulling the following codes:

My truck is cold during the test.

173 Lack of Heated oxygen sensor switches indicate rich bank 1

137 Lack of Heated oxygen sensor switch during KOER indicates rich bank 2

538 Insufficient RPM change during dynamic response or goose test KOER or INVALID cylinder balance test due to cylinder identification sensor failure

536 Brake On/Off circuit failure not actuated during KOER test