Guys I was on here for a few years when I had my Ranger so it's changed here and is like a totally new site. I am currently banging my head trying to figure out a stalling condition on a 1990 F-150 with a 5.8L and 2wd. Starts up fine and fuel pressure is good, battery and charging system are good (charging @14.5 vdc) and grounds are good. I took the IAC and the EGR off to clean. I did a spark plug, plug wire, cap&rotor tune-up on it and changed the fuel filter. New air filter too. Truck starts and hovers @ 600 rpm, stumbles a little but catches itself, and then will die within a minute or so. Drives great and so far hasn't stalled in gear (but I've been told it does). Repaired a few vacuum lines that run along the passenger side near the exhaust manifold. I'm getting 12v at both the EGR and the IAC and both grounds there are good too. Scratching my head...and losing hair over this. Any input welcome to save this old gem.

 

i would check ALL the vacuum lines, and then the coil

 

If you have both 12V and ground at the EGR Solenoid then the EGR valve is all way open and could cause this problem.

You should not have a ground until you have a warm engine and are at hi-way speed but not WOT. Never at idle or with the engine not running.

 

The EGR solenoid is a three wire and you are saying that ko/eo (key on/engine off) I should get 12v but no ground through the solenoid wiring harness? What are the three wires? Should I get 12v and also a 5v for reference? Out on it right now..

 

You only have two wires on the EGR solenoid. The EGR solenoid is located over by the Ignition Coil.

If you are talking about the EVP sensor on top of the EGR valve it has three wires, a ground, +5 VDC and a signal return wire.

 

Aaaahhh, ok, gotcha. so ko/eo no ground and then ground with engine warm?

 

BTW........thanks for your help so far

 

could be a shot fuel pump too. Able to prime the system & start, but does not stay running after prime

 

Yes for the solenoid over by the Ignition Coil.

 

Just probed the red wire and got 12v (assuming I'm in the right spot). Is the EGR solenoid just in front of and to the passenger side of the coil? I'm tracing the two vacuum lines that go from it (green and red) along with a red wire and a green wire.

 

This thing runs great outside of the idle issue. The trucks condition is overall excellent and has lead a good life (mechanic owned). 332k miles are taking their toll.

 

ok, I'm boggled. KO/EO I get 12v on the red wire at the egr solenoid. KO/ER (running and cold) I get 12v on both the red and the green wires...that can't be right, right ?

 

Yes that is right, when the computer is not grounding the solenoid (no ground) then you will read voltage on both sides of the coil of the solenoid.

By the way that 12 volt red wire is common to all solenoids, fuel injectors and the fuel pump relay, it comes from the EEC power relay.

 

So I'm looking at an ECM fault? I know the EGR should be open at cold start/idle and then close after warmup for other vehicles...this one work that way too?

 

As far as I know all vehicles the EGR valve is closed durning cold start/idle and then opens after warm up an running on the road.

If the EGR valve was open at idle you would have idle problems.

Sounds like yours is working right.