Well, before I tackle this one, I'll take some opinions.
'94 4.0 extended with automatic. Check engine light has been coming on intermittantly and then finally stays on after driving about 20 minutes. We've had some strong winds here lately and driving into the wind it has absolutely no power and has a top speed of about 50 mph. With no wind, it drives great once it warms up. Pretty lethargic when cold. New fuel filter, and, because it had the original one on, at 150K miles, I put on a new O2 sensor. MAF was cleaned with an aerosol maf cleaner.

Checked the codes and, wow, I didn't think it could store that many. I've got the following codes: 85, 72, 87, 31, 91, 86, and an 82. That's after driving about 45 minutes after the codes were completely cleared.

As I don't consider myself a parts replacer, I'd like to find a spare ecu just to see what happens. Any ideas? I'll keep you informed.

 

I have looked up the code you getting there as follows:
85: Canister purge circuit failure
72: Insufficient manifold absolute pressure (MAP) change during dynamic response test
87: Fuel pump circuit failure
31: EVP circuit below minimum voltage
91: HO2S circuit Indicates system loan (left HO2S)
86: Shift solenoid circuit failure
82: Secondary Air Injection Bypass (AIRS) solenoid circuit failure

I'd say you just have a electrical/power problem, Its your aerostar up to date on recalls? This is a recall for 1994 aerostar, sounds a bit like the problem your having.

1994 Ford AEROSTAR Recall ID from NHTSA: 99V028000
Auto Recall Date: 02/09/1999
Vehicle Component: ELECTRICAL SYSTEM:WIRING:FRONT UNDERHOOD
Estimated Vehicles Affected: 23097
1994 FORD AEROSTAR Defect Summary:
VEHICLE DESCRIPTION: MINI VANS. HEAT GENERATION IN THE WIRING HARNESS TO THE FUEL PUMP/SENDER ASSEMBLY CAN CAUSE AN ELECTRICAL SHORT. THE VEHICLE COULD EXPERIENCE A LOSS OF POWER AND BECOME IMMOBILIZED AND THE FUEL GAUGE MAY BE ERRATIC.
Defect Consequence:
HEAT DAMAGE, INCLUDING MELTING OR CHARRING OF THE FUEL PUMP AND SENDER ASSEMBLY WIRE HARNESS AND ASSOCIATED WIRING HARNESSES CAN ALSO RESULT. THE SHORT CIRCUIT COULD ALSO HAVE THE POTENTIAL FOR A VEHICLE FIRE.
Remedy:
DEALERS WILL INSTALL A FUSED JUMPER HARNESS IN THE FUEL PUMP GROUND CIRCUIT THAT WILL BE INSTALLED AT THE FUEL PUMP INERTIA SHUT-OFF SWITCH.
Notes: FORD MOTOR COMPANY, 99S01

 

Just by the FEEL of it, I'd say a fuel pressure regulator problem, but it will throw all those codes in a matter of a couple of minutes. I read the codes right before I posted them and I won't have time to work on it for a few days. I'll keep you informed.

 

also take a close look at alternator load test, battery load test, batt. connections and negative lead connection block connection.

 

Well, I got it fixed.
I'll tell you what it was.....but first I have to rant a little bit.
I've never really liked the OBDI system. I know it was probably good in it's day, but the codes can be vague. (As in this case)
Anyway, the problem was.......Mass Air Flow sensor.
It was a lucky guess, but I managed to guess correctly.
Now for another rant.
Nobody around where I work had one in stock, so I had a cousin pick one up for me. He works about 25 miles away and he picked one up from a national discount chain. (Which will remain nameless)
It was a rebuilt one with a one year warranty.
Anyway, my gripe is that it looks like it was pulled right out of a salvage yard. It was not cleaned up at all and had all kinds of dirt on it. Maybe somebody used it awhile and took it back, I don't know.
The new one that their catalog lists wasn't in stock or I probably would have purchased it. Whatever.
Anyway, the van now runs good and has good power. Economy will be tested this weekend with a 6 hour drive.
I'll check on the recalls next week. Anyway, thanks for the comments.