First time here hope to stay nice forum. Anyway I'm not a mechanic but here goes. I bought a 94 4.9 F150 back in May and have'nt been able to get this thing running right. My daughters boyfriend and I have been doing all the work on it. The problem is it is running rough when giving gas. Does the same when shifting into park. We hooked up a computer shows all vacuums ok but running rich.
This is a list of all things replaced already. O2 senser,plugs, wires, cap. Throtttle body gasket, injectors,fuel filter.
I'm going to try some throttle body cleaner this weekend. After that we don't know. Oh the truck has 110k on her.

 

run a fuel pres. test.it should be 60 psi. you could have a bad fuel pres. regulator.pull the vac. line off of it and see if fuel comes out when you key it up.

 

change plugs. you did not say if you did already but do it again even if not that old. cheap and easy. use motorcraft regular plugs. imo.

 

I just changed a month and a half ago. I replaced all parts with original Ford parts. I will check the fuel pressure for 60psi.

Thanks guys, Daman

 

Sounds like a FPR to me. Easy and cheap to replace and will save ya about 5 MPG compared to probably what hes gettin now.

 

Have you ever had a check engine light on your dash board??
Did you pull the codes from the computer? It is easy to retrieve stored error codes from the computer as a diagnostic aid. Equipment needed, paper clip, pencil, paper, and thinking cap. Browse fordfuelinjection.com for the test to retrieve 3 digit codes.
PS/ Don't throw those injectors away! I hope you are well off, the injectors are expensive, they last a long time. Maybe you can clean them up and sell the old ones.
The fuel pressure regulator is 40 bucks at NAPA, and usually works fine until the diaphraghm breaks and leaks gas into the vacuum line. Be very careful handling vacuum lines on that engine, the plastic, thin, color-coded lines are very brittle and snap like dry pasta, if you man-handle them. The FPR is on the fuel rail, under the upper plenum, just above the #1 and #2 cylinders of the engine( towards the front)and is held to a fuel-rail bracket with three small allen-head bolts. The only line going to it is the vacuum control, originally the line was plastic tubing and had a rubber boot with a 90 degree elbow, the boot of course attaches to the port on top of the FPR. IF fuel is observed leaking from the FPR at the vacuum port then the diaphragm is shot.
Otherwise I would leave that alone until you can perform the test to retrieve the codes.

Another inexpensive and useful repair is cleaning the IAC, search IAC in the 87 to 96 forum and you should get alot of hits.
BTW, I use Seafoam to clean my intake manifold and TB.

 

Never had any check engine light. Ran like this when I bought it, thought it was a tune up needed lol. We already disconnected the FPR and no leakeage. I'm waiting to check the fuel pressure, daughters boyfriend should be able to get his hands on something. I know the injectors are expensive ran me $325. Should have stuck to my old Chevy lol, JUST KIDDING! Anybody want some old injectors? Oh forgot to mention no codes came up from the beginning just running rich.

Thanks again all, Daman

 

No codes is great.
BTW, the computer can generate codes, problems will be recorded and stored, even though the CE light didn't flash on.

Check your codes once in a while, the codes will be erased if you pop the battery off for a few minutes. Intermittant problems may show up a few days or a week later.
I'll pop the hood and start a test to see if there are any codes every two to three weeks.

The rough idle situation could be related to carbon build-up, I would really investigate the options of cleaning the IAC ( on top of the throttle body, just above the plates), and Seafoaming the intake manifold,.

 

Test the ECT on the block. Engine coolant temp sensor.
(i can';t type today!LOL)
Popa Tim

 

An exhaust leak upstream from the O2 sensor can cause an overly rich mixture, too. Air gets sucked in so the computer thinks the engine is lean.