Posted before, problem is worse. 297,000 miles, new fuel pump. Fires off but skips wildly, as if it's going to shake your teeth out, may smooth up, may not. Might do it today, may not again for 3,4,5 days. Use BP or Shell midgrade, religiously. Sometimes bleeding the fuel system at the Schraeder valve will help it start, might not. Once it smooths up, no problems- runs like a new one. No miss under load or at any speed. 16.5 mpg consistently. Ambient air temp does not affect it. Might/might not do it with engine cold, might/might not do it with engine hot. I'm a Ford man all the way, but this is out of control. Any ideas? This must have happened to someone before. Any help greatly appreciated.
Thanks for the reply. No, no real testing as of yet. Seems to me that any of the ignition components will either malfunction at low idle or high speed, under a load. That's what I keep saying - this rough idle only lasts for a minute or two then the engine runs like new. There has NEVER been a problem with it missing under load. Additionally, it will crank and run perfectly for several days at a time. Defective plugs, wires, etc. would not "fix" themselves. Once they fail, that's it, it never gets any better. This problem occurred 5 times today with 1 time in between that it cranked like it should. Either vigorously pumping the accelerator or bleeding the fuel rail will make it crank. Incidentally, fuel level in the tank is not a factor - makes no difference if it's slap full or close to empty.