1990 Ford E-350 with 5.8 L V8 ECC IV/EFI system

Problem:
Doesn't idle. Starts for a few seconds and then dies.
Runs very rough if engine is reved.

Tests:
It is OBD I. I get no DTC codes with KOEO, can't get a reading with KOER.
When I spray starter fluid in "throttle body"... the engine will idle (butterfly closed).
Unplug "idle valve" it will not idle, even with spraying starter fluid into throttle body.
Injector manifold 40 psi, engine off, but key on.
Inline high pressure pump and tank pump are running ok.
I get 10 oz of fuel out of injector maniflod after running pumps for 10 sec.

More tests:
Vacuum tested the "Fuel Pressure Regulator" it's OK
Tested the MAP frequencies with vacuum pump and frequency reading multi-meter.
0"=121 Hz, 5"=107 Hz, 10"=96 Hz, 15"=85 Hz, 20"=73 Hz
NOTE: engine idles and runs smoothly with MAP vacuum disconnected!
Engine vacuum at idle is 18"
Using vacuum tester connected only to MAP, engine idles best at 5"- 7".
If I connect the vacuum line back to the MAP (18" at idle) engine dies.
Is it a defective MAP or are we tricking the ECU and something else is wrong?

 

Good chance the MAP sensor is shot, would cause this type of running problem.

Check this Link, page 2 has the Vac reading that you should have, or close too, the reading you posted are off by quite a bit.

If the MAP is not sending the correct signal back to the ECU, the ECU will shut the fuel pump down, lack of fuel, no run.

 

IT WORKS !!! I replace the MAP sensor and my van is idling and running fine! I was a concerned when I tested the MAP and got a consistent change in frequency with increase in vacuum, but I guess they were the wrong frequencies.