Hey everyone I just recently recieved my dad's old 93 f-150 2x4, auto with the 5.0L. During the 10-12 years that he's had it it has never given him a problem and he's only had to replace the radiator and a driver's side exhaust manifold, and clean the EGR. The original owner before that kept impecable service records and both him and my dad have only used Mobil1 in the engine.
But here's where it gets tricky after my parents drove it a 1,000 miles up here I have it for a week and then it doesn't want to start. When I can get it to run it sounds like it's surging, stumbling, or running lean. I replaced the fuel filter and it seemed to fix it (altough I think it was more because I reset the computer). Couple of days later it starts to act up again so I pull codes from the truck and get 23 and 34, which are for the Throttle Postion Sensor (TPS) and the EGR Valve Position Sensor (EVP). So I first check the EVP, it reads good voltage but it's slightly low on ohms so swap it no change so put the old one back on. Then check the TPS and it's a little low on volts at idle, supposed to be .9v and reads .86v so swap it with a new one. By this time the problem corrected itself but came back the next day.
Took it to Performance Ford and they kept it over night to tell me the next day that they couldn't duplicate the problem and the only codes they could pull where the EVP and TPS. So basically nothing new, but they atleast could tell me that the O2 sensor, fuel pressure, and alternator where good. Drive the truck home and it does perfect for about a week and then it starts to act up again. Same problem surging and stumbling like it's running lean and sometimes dies when I step on the brake. So I'm thinking it might be a vaccum leak so I check all hoses and gaskets and nothing.
So then I read online from other peoples post that the problem could be caused by a clogged Idle Bypass Valve so I take it off and clean it with the EGR and put them back on. No change so now I'm back to square one the truck has trouble even starting and when it does it promptly dies. The thing that gets me is that it's random, even in one drvie it could come and go then not show up for a couple of days. So I'm almost positive that it's something easy and electrical, I just don't know what.