Hey guys, i posted here a long time ago and got some really good help I have a 1986 F-150 V8 5.0L EFI engine. I have a question about the EGR, cuz it runs rough and crappy every once in a while, and i know the problem has to do with one of the sensors or something. Ive replaced the O2, the MAP,the TPS, brand new throttle body done valve cover gaskets, new intake plenum gasket new fuel pumps (external and internal) and the vacuum lines seem to be fine, but i dont have a complete truck to look at and judge against, thus a question, ive come down to 2 possible things causing my occasional running problem, with wierd idling and rough running, are the TPS or the EGR valve, well, this morning, i changed out the TPS and while i was at it put in a brand new throttle body, and pretty much made that baby brand new, but it didnt solve the problem, so, im looking at the EGR valve. Ok, the green vacuum that goes into it, is it supposed to be sucking or blowing?? cuz it isnt doing anything. Please let me know...., oh and the black thing that looks like a can right next to the battery, it has red and black vacuum lines coming out of it, well, the black one was disconected, and there was a broken end of this yellow piece of plastic where it looks like that black line went into, and this piece of plastic goes into these three electrical connector things, and they have three vacuum lines coming out of them, one going to the EGR and the two others having to do with the pollution control system which i dont use. Any help please?

 

Ok, i fixed the vacuum line to the yellow plastic all vacuum system is up and running the way it should be, no leaks anywhere. Engine is still runnin rough and rough idle....could it be the EGR itself? maybe something else?

 

hey, I know I;m not much help but I have the same pickup and engine and was wondering if you had put a cold air intake on it. If so what make and model is it because I'm looking for one and can't find jack. Thanks

 

Nope. Its all stock.

 

If the EGR is sticking open it could indeed be causing the engine to run rough, especially at idle. I'd advise you to remove it for inspection, see if you can tell if it is sticking. After buying all that other stuff and EGR isn't that bad, about $90.
DannyP

 

How do u get the EGR off????? its 2 bolts, and then its connected to a tube thas connected to the lower intake manifold do i have to pull the whole tube, too? cuz where the EGR connects to the tube, it just wont budge, and i dont want to break anything...

 

It has to come loose at the tube. It'll either budge or break. You may try soaking it with WD40 or something similar for awhile. Take your time, don't bust a knuckle.
DannyP

 

You can test the EGR valve and see if it's working by applying manifold vaccume to it. (That's how California smog techs test them during smog checks)

If the truck idles down and runs like crap, (with vaccume applied) then it's working.

If it doesn't change the idle when vaccume is applied you need to replace it, (it's either stuck open or the vaccume baffel has a rip in it.)

The EGR Valve should not have vaccume going to it at an idle. If it has vaccume at an idle then one of the control solonoids, (carburetor ports on earlier models) or a miss routed vaccume line would be suspect.

hope this helps...

 

I have an 86 f-250 and am having the same trouble. Did you bypass the EGR valve by diconecting and plugging the end of the hose line? I know my problem the the valve itself. My BIG problem is trying to find the part since it was dicontinued in 1994 by ford. My truck is a Canadian made and the valve has 2 vacuum ports on it. Hope this helps you ...

 

Any autoparts store should be able to get it. You didn't state what engine you have but Advance Auto Parts online shows valves for both the 5.0 and 5.8.
DannyP

 

Ok. I now have tried the EGR and it is in perfect working order. Now i am completely lost. it has brand new O2 sensor, brand new MAP sensor brand new TPS sensor, brand new ignition system, includin coil and everything. Any ideas???

 

How did you arrive at this conclusion? Are you sure the EGR plunger completely seated in the closed position? This may be difficult or impossible to determine without removing the valve.
DannyP

 

Applying manifold vacuum to it, and it bogged.

 

You could be in the same boat I'm in!
'86 150 4x4 5.0L
Have the engine scoped out.
do the cylinder shorten test.
When you shorten out a cylinder, naturally the engine rpm should go down.

On mine Cyl 1, 2, and 3, when I shorten them out, the engine would rev UP!

This showed the the valve guides in 1,2,and 3 were shot.
A cylinder compression test, the engine will pass. but running, it would be smooth sometimes, and rough others.
My engine is out being re-built as we speak!

Have it scoped out to rule this out.

I bought a snap-on Counsellor oscilloscope on e-bay (only $370!!!) they are over 2 grand new.

Hope this helps
Reamer

 

It's still possible, now that you did this test, (at least the valve works) that the valve is dirty, and not closing all the way as it should. It may need to be cleaned.

When you did the test and released the valve did the engine snap right back to the original idle, or does it fluctuate? Apply and release manifold vaccume to the valve a few times and judge by ear. If the idle snaps right back and doesn't fluctuate, each time, I'd look for another problem. If the idle fluctuates each time you release the valve, then I'd take it off and inspect.