I hate to have you replace random parts but part of the problem could be the battery. That is a REAL common problem with GM vehicles but I haven't really heard of that on Fords. GM generators develop a lot of voltage spikes that interfere with the Engine Computer's sensor signals. A good battery dampens and absorbs those spikes. Sometimes old batteries still start the engine just fine but they lose their ability to dampen those spikes. The clue is the engine runs better when the generator is disconnected. It can't produce those spikes then.
One thing you might try, if you have access to a battery charger, is run the engine and disconnect the generator when the problem is acting up, then see what happens when you turn the charger on at a low rate. That will produce very high "ripple" which is a variation in the system voltage. You measured 14.3 volts, which is perfect, but the system voltage is actually bouncing rapidly between about 13.0 and 15.0 volts. That variation is what the battery should be smoothing out. The battery charger, by its very nature, puts out much higher ripple than the generator. If the running problem comes back when you turn the charger on, I would suspect the battery first but there's no way to know for sure except by trying a new one. There could also be a computer with a problem with its internal regulator circuit that makes it behave erratically from the voltage variations.
One more thing to look at are the various ground wires. There will be one small ground wire going from the negative battery cable to the body. Also look for any cables or straps between the engine and body that are corroded off.
Saturday, April 2nd, 2011 AT 6:46 AM
