I think I have some serious ignition issues on my 1990 F150 6 cyl. If I ease on the gas I can rev it up to 4500, but if I mash it, it just putts and stumbles. I am wonering in the this is a PIP or TFI issue. Possibly even a TPS problem?

Any clue?

Thanks

 

Sounds more like a fuel filter.
If the filter is OK, check your fuel pressure at the rail with a gauge while grounding pin #6 of the DLC with the key on. Should be about 55 psi.

 

I changed the filter. I would think that if this were a fuel problem, it would not want to rev up at all, however I can rev it up some but only if I do it slowly. Is my thinking wrong?

Thanks

 

When you say rev it up slowly I think you mean in park (out of gear). If so you do not use much gas and you do not have to open the throttle much to rev up an unloaded engine.

I take it we are talking about an engine that has had new plugs, wires, cap, rotor, air filter and is in time with no vacuum leaks.

I think the first step would be as it will not cost you anything is if you do not have one is to rent (you get all of your money back when you take it back) a fuel gauge from an auto parts store. While you are there have them try an pull your codes.

Put on the gauge, ground pin #6 of the DLC (Test Connector) with the key on and you should get about 55 psi with the engine not running. Check for leaks.
If you can not get up around 55 psi then you have a bad FPR or Fuel Pump(s)
Note that the fuel pump will only run for two seconds when you turn the key to on, the PCM (EEC) will not allow the fuel pumps to run with out the engine running except for the one to two seconds to pressurize the fuel system. This is a safety thing to prevent fire.

Now un-ground the DLC and see how fast the pressure drops, it should hold or drop very slowly.
If it drops fast you have a bad Fuel Pressure Regulator, Check Valve(s) in the pump(s) or a leaking injector.

The other items you asked about should show up if they are bad when they pull the codes at the auto parts store. You can pull the codes yourself if you want to, just ground the STI connector, get paper and pen, get behind the wheel and run the tests, you count the flashes that the MIL makes.
If you do not know how to run a self test go here:
http://fordfuelinjection.com/

STI - Self Test Input circuit
MIL - Malfunction Indicator Light
EEC - Electronic Engine Control
DLC - Data Link Connector
FPR - Fuel Pressure Regulator

Here is a diagram of the DLC.



Here is a diagram of your fuel system.