Vehicle: 1989 F-150, 302, 5 speed manual.
Symptoms: A few days ago the idle started "hunting" from 600-1100 rpm and started from stop with stumble. This symptom was erratic but was livable. Put on friends diag computer and came up with O2 sensor, ego not shifting, and insufficient egr. Later that day it just quit and would not restart unless I hold throttle to the floor and then hold at over two thousand rpm but eventually loads up with fuel and quits. Way, way rich. Checked ego, temp sensor, tps, map sensor, and all ok. Changed O2 sensor, cap and rotor, no help. Put vac gage on, only has 2" vac on cranking with throttle butterflys shut. Checked all hoses and brake booster with mityvac and everything held. Thought timing chain jumped, but with #1 piston on tdc rotor is on #1 wire. Checked egr with mityvac, no leaks and pintle seals great. Good fire to plugs, coil good. Almost acts like it has a catastrophic vacuum leak but cannot find. Could CPU be shot?
Any help from anyone would be greatly appreciated.

 

If it is indeed rich as you indicate I would first need to check the fuel pressure regulator for a bad diaphram. Remove the vacuum line to the regulator and see if there is fuel on that side of the diaphram. If so replace it and then change the oil. If you can't tell for sure crank engine with vacuum line still off and look for fuel coming out of regulator. If regulator checks ok maybe TPS is out of specs. or possible that an injector has stuck open?

 

Dummy me, it was the fuel pressure regulator. Replace it and it funs fine. Thanks for the help as this is my first computer vehicle. :-))

 

Glad I could help.