I got my van up and running after its 18 year nap in a church parking lot. The motor runs very well the van has extremely low miles, i put in new fuel pumps, tank, filter, pressure regulator, and injectors, but it appears to be running rich. There is alot of un burned fuel comming out of the tail pipes (dark black smoke at idle and liquid fuel), any suggestions? it does seem to have a vaccum leak causing the RMP's to surge at idle could that cause it? Besides that it runs well, has pleant of power no ticks or taps, cools properly, doesnt burn oil, and shifts very smoothly, starts immdeiately no matter what temperature it outside.

 

Are there any codes (CEL)?
It might help to know the actual fuel pressure.
You suspect a vacuum leak, but that usually causes lean conditions.
Maybe you can check the ECT sensor.
I bet you cleaned the MAF sensor with MAF sensor cleaner and the throttle body with throttle body cleaner already.
Whether this is the cause of your rough running or not I would clean the EGR system, PCV system and check the EVAP system as well. Even the O-ring under the oil filler cap deserves a look.
Did these vans have a DPFV? If it is made of metal it is likely corroded.

 

I bet his fuel pressure regulator is out of it it stuck shut and allowing the excess fuel to go into the intake manifold

 

I checked the fuel pressure, and it was correct, I have not yet cleaned the MAF sensor but will asap, the Fuel pressure regulator is brand new but could be the problem, isn't it vaccum operated or actuated?

 

I don't know how it is in your application but when you have look you will know right away. If there is a vacuum line than it reacts on a vacuum signal.

Just considering the long sitting time of this vehicle I would inspect, pull off, blow through, possibly replace all these vacuum lines anyway.

 

The surging sould be caused by a small enough vacuum leak that the IAC is having troubles compensating for it. Easiest way to verify if you have a vacuum leak is to remove the air cleaner before the MAF. Then, with the engine running slowly start blocking the air intake off by cupping your hand(s) over the intake. If the engine idle smooths out and the surging stops, then you have a vacuum leak. At this point, happy hunting. Look at all rubber vacuum hoses, especially where they connect and any with bends as these point deteriorate over time.

 

I should have mentioned that i replaced all of the vaccum lines when i pulled the intake manifold to replace the injectors. as you guys have mentioned they were all rotted. search for the leak this weekend, could this cause my rich condition?

 

Being a 1991, you have the OBD-I monitoring system. As such, you could have a bad O2 sensor or O2 sensor wiring. A bad O2 sensor reading can cause the rich condition you are experiencing without setting any type of code. If I'm not mistaken, there is only 1 O2 sensor on the OBD-I systems and it sets in front of the catalytic converter.

 

If you decide to replace the O2 sensor consider getting it from Ford . Have been there with "universal" oxygen sensors never right !