Mattstunt929

I got a 93 f150 5.0 160k miles. When I first start it up it idles up then down to the point where it's about to die then comes back up. After that it purs like a kitten.
Going down the road with the motor cold, it feels like its got a bad miss. It will keep running like it has a miss until the truck warms up. Then it smoothes out. Seems like its affecting gas milage as well.

I've changed the plugs, wires, cap and rotor, and the iac valve.

I'm starting to run out of ideas please help!!!!!

Mattstunt929

I've also replaced the tps sensor and cleaned the throttle body.

oldmanb777

Winter blend gas maybe? What about the fuel pressure regulator? Maybe water temp switch? Not a good temp indication while cold. That may not set up a code on OBD1 Vacuum leak?

Rusty but trusty

Pull codes

Mattstunt929

Wouldn't the fuel press reg be constant hot or cold? Not familiar with the water temp switch? Temp gauge is working properly.
I will figure out how to pull codes and let y'all know.

oldmanb777

The fuel pressure regulators on both of ours started leaking fuel into the vacuum system. Ran just like you described, EXCEPT, as you guessed, they did it all the time. No codes. Easy to check. Just pull the vacuum line and check for fuel in it. But I would think whatever is cut out of the system until the engine is up to operating temp, is the problem. That all starts with water temp. The system will attempt to run a little rich until up to operating temp.

Mattstunt929

Well I checked the press reg last night by pulling off the
Vacuum line and no gas. Will try and test the temp switch
Tonight when I get home.

Mattstunt929

Just got home, checked the ohms on the temp switch and got a reading as an open circuit(testing unplugged at 210 degrees) will be replaced. But....I did notice a couple other things as well.

It appears to be missing a vacuum line coming from the coffee can looking object. It has a red line going to it but it appears there once was a black line coming from it that has now disapperared. Where does the black line run to?

Also I noticed that I can unplug the egr valve and noting is affected. Is this normal.

Crowder

I'm having this issue myself. Interested to see if you find a fix

Brandon587

I'm pretty sure the black line runs to your intake manifold.