Hi there. As my name would suggest I really did jump in the deep end on this one. I recently bought a 1988 F150 4.9 I6 Manual from an individual owner. It has about 160k miles in it. The truck ran fine when we picked it up. All symptoms developed over a period of 2 or 3 days and have gotten progressively worse, before being parked.

Symptoms
Lopes and tries to stall but smoothes at higher rpm.
Seems to miss on one cylinder.
Heavy Black carbon deposits on all plugs.
IAC and O2 sensors helped cut back on the black smoke, but did not solve the problem.

Vacuum
-Replaced all vacuum hoses
-Checked for leaks at or around the throttle body
-Is pulling 29-30 in Hg. at manifold vacuum tree and similar throughout

Ignition
-Replaced distributor cap rotor
-Replaced wires and spark plugs
-Good spark off ignition coil
-Checked timing
-Checked compression 150-155 psi. on all 6 and holds

Fuel
-Checked fuel supply pressure 48 psi.
-Fresh fuel

Valves and Sensors
-PCV valve and filter replaced (breather valve on my model)
-Idle Air Control replaced (IAC)
-O2 sensor replaced (as far as I know my model only has one)
-Throttle Position Sensor replaced
-EGR appears to be good
-Took battery cables off for mater reset

General Maintenance
-Serpentine belt
-Radiator, thermostat, upper and lower hoses
-Upper and lower heater hoses

I would greatly appreciate any input or ideas. Cause I am all out.

 

I don't see it listed, but I'm sure you replaced the air filter? Fuel injectors is the only other thing that comes to mind. If you can run, or better yet, drive it I would try some fuel injector cleaner in the gas tank. Otherwise I would consider replacing the fuel injectors.

 

fuel pressure regulator- any fuel in the vac hose?
did you set the tps?
did you pull codes?
maybe remove the TFI as last resort and have it tested at the parts store.

fullsizebronco.com has more info on all of that.

 

First, I'd put the original O2, TPS, & IAC back on. They're probably better than the replacements. Second, STOP replacing parts until you find one that fails a published test. Did you set the timing according to the instructions on the VECI label under the hood? Did you route the wires properly? Does the EEC stink like burned electronics? Can you hear the valves/lifters rattling more than normal? Have you changed the oil? Do you buy gas at the station where the PO did? Is the truck rusty? Has it ever been wrecked? Is the exhaust completely stock? Click these & read the captions:

. . . .

Try to find a red-cover Haynes and follow the diagnostic procedure in Ch.5 (usually Sec.5 or 7).