Timing is dead on, total advance is just under 28 degrees. Yes it has a mass air unit and, as per my more reputable mechanic, it is working correctly. TPS is in range and working correctly. There are no active or hardcodes in the ECM. This hesitation problem occurs hot or cold. It tends to be more preveliant when it's hot and the probem is getting more frequent. When it starts to act up, if I blip the throttle a few times, it will correct itself. We've checked the fuel pump relay and all it's associated wiring. They're ok. We changed out the ignition module, at a suggestion by the local Ford dealer. That didn't correct the problem. The one thing I notice, the fuel pump wines, rather loudly once the truck is up to operating temp. When the hesitation starts, I notice the wine goes away with the motors starting to hesitate. We put a fuel pump pressure gauge on the pump and it shows 22 psi. Just for shits and giggles we r&r'd the pump and filter and it did nothing to improve the system psi. The problem with this problem is, it's not consistant. Although each of the 3 mechanics who've looked at the truck have experienced the problem first hand, when they've gone to do checks on the motor, it runs perfectly fine. It's a Ford Each of these three mechanics have told me they consider this to be a fuel system problem. They're concern is that the fuel PSI is within the tolerence, it's just on the low side. There has also been a question that the fuel system may be vapor locking, due to the low fuel pressure. But, correct me if I'm wrong, EFI fuel systems aren't supposed to vapor lock, are they?
Thursday, May 3rd, 2007 AT 8:32 PM