I have been having hesitation/stalling on acceleration with my 99 Expy 5.4L.
I brought it to Pep Boys for a diagnostic, thinking that it was vacuum related.
Last week, I found the vacuum elbow near the side of the intake manifold was wide open. I replaced that with a spark plug boot.
Anyway, Pep Boys called me and said that 7 different code came off the ODBII, including throttle position sensor, cylinder heat temperature and something with the fuel. Sorry I'm vague about the errors. Hopefully, they'll be written on the sheet when I pick up the Expy. The service person said that with all the errors, it might be possible that the computer is going. I'm just looking for some opinions from everybody. If it is the computer, how much will that cost to replace and do I need to do that at Ford? Pep Boys said that they won't even charge me the diagnostic fee as a courtesy.

 

Get it back. Unhook the battery for about 30 min. Then drive it and see how it runs. If the CEL comes back on, take it to AutoZone and have it scanned for free. Post the codes here and we'll see what's going on.
You can also post your codes from PooBoys and well see what they say. I'm not real fond of their service dept.

 

I'll be picking it up tomorrow. I gave them the ok to work on my brakes (I didn't have any). I lost all the fluid from my master cylinder the other day. I refilled it and pumped the brakes a few times and saw a puddle under the front left. I checked the engine compartment and saw fluid near the antilock module. It turns out that the line from the master cylinder to the antilock module was all rusted and broke open. Luckily, I discovered this before getting on the highway, and was able to take the streets back home.
I'll let everyone know the codes that Pep Boys found. I'll also clear the codes and run it around to generate some new ones.

 

I picked up the Expy today. The brakes work fine now. Here are the ODBII codes that Pep Boys picked up:

P0460 - Fuel Level Sensor Circuit Malfunction
P1285 - Cylinder Head Over Temperature Sensed
P1501 - Electronic Throttle Monitor Malfunction
P1299 - Cylinder Head Over Temperature Protection Active
P1309 - Misfire Detection Monitor not enabled
P1254 - Pedal Correlation PDS2 and LPDS High
P1124 - Throttle Position Sensor out of Self-Test Range
P1000 - OBD-II Monitor Testing Incomplete

After I brought it home, I disconnected the battery for 30 minutes, then reconnected it. I haven't driven it anywhere yet, so I'll keep you informed if any codes pop up.

Keith

 

P1501 - Vehicle Speed Sensor (VSS) Out Of Range
P1254 - Throttle Position Sensor Out of Range

I drove the Expy today and it hesitated and lurched around once I got to about 40MPH. The tachometer went from 1500, down to 0 then back up to 1500. The theft light started blinking while I was driving, too.

 

Sounds like you may have a bad chassis ground. Check all of the ground wires under the hood. A bad computer ground can make all kinds of wierd things happen.

 

Today, I checked a couple of the ground wires under the hood with my V-O-M. I had continuity. I also looked at the harness under the dash leading to the computer. Everything looked ok there. I'll probably bring it somewhere else for diagnostics.