97 f150 flashing check engine light and chugging

97 f150 4.2 v8. driving to work this morning and got about half way (10 miles) and my check engine light started flashing and the truck started chugging. had to keep jacking with the accelorator to keep it running as there was no place to pull off the road safely. then the light quit flashing, stayed on steady, and the chugging went away. i had a steady check engine light on for a couple of days before it started flashing, but i was blaming that on cheap gas and i had put a bottle of injector cleaner in the tank. i don't know if the weather has anything to do with it, but it went from the mid 30s yesterday to the upper 40s this morning and extremely high humidity (3 inches of snow melted and misting rain). i've had a check engine light in the past on it and the codes (i can't remember which ones) pointed to EGR, but the mechanic at the garage had me run injector cleaner through it and it cleared. any ideas?

Has it been tuned up lately? The flashing light means the converters are being damaged as the engine is running. This usually is caused by an engine misfire.

been a while since the last tune up, going to do it this weekend. an interesting twist to the problem, got in it after work to see how it would run and it was running okay, no check engine light either. started on the way home and suddenly it started running kind of like an old school carb vehicle with a stuck choke, loping and chugging. did this for about 3 minutes and then started running fine and the check engine light never came on. ran great all the way home, got home and it sat for about 30 minutes, drove it to the store and hit a puddle and the engine light came back on, but running fine. kind of wondering about a bad plug wire getting moist. hoping oreilly's is open and has a code reader so i can get that done.