300 I6 EFI Power issues/ rough idle
 

I drive an 87 f150 with the 300 inline 6, 4 on the floor with a granny gear, efi. Replaced the TPS, cleaned the EGR, new vac lines, air filter, fuel filter, plugs, wires, distributor rotor and cap. Just recently started surging at startup idle for a bit before settling out, and now I'll get on the gas and it feels like the engine is bogging down before finally and suddenly picking up, only sometimes idles rough. No water in the fuel. After searching around in the forums quite a bit, I'm suspecting it's either the high pressure fuel pump, (low pressure in tank pumps are fine, runs the same off either tank) fuel pressure regulator, ignition coil, or idle air speed control valve. Any insight? I have yet to test fuel pressure, but I feel it might be my fuel tank selector valve may be sticking and not allowing max flow, because it already has cross filling issues from the rear tank to the front, but that's been happening for a while.

Definitely check fuel pressure, that motors requires upwards of 55-60psi at the engine at low vacuum conditions to operate correctly and existing problems with the selector valve could definitely impact that.

Getting out and testing pressure today, I'll let you know the results. Hoping it isn't my fuel system.

Tested fuel pressure this morning. In the 45-50 psi range at idle, which seems normal. When I pulled the vac line to the fuel pressure regulator, the psi jumped up to 60 and the engine idled a little quicker. No smell of gas or anything in the vac line either. Not sure what to make of the psi jump. Throwing in a new ignition coil, we'll see what that brings.

Before tossing more $$$ at it, pull the codes from the ECU to see what if any codes are present.

Your fuel pressure is good and yes it should jump to 60psi with vacuum removed from the regulator so there is nothing wrong with your fuel system. Next step is pull the codes and post up what you get.

Pulled codes and the only thing that came up was the bad voltage from the tps. This is odd, because I just replaced it last month. I'll give it the manual voltmeter test tomorrow and see what it does though. That's how I found the old one was bad. May have a bad wire somewhere in the harness too. Cleaned the IAC valve and that helped a bit.

im thinking your iac valve. cleaning it can help but me nothing like a new one.