EGR vacuum line troubleshooting

[Gsmblue]

I will readily admit, I am out of my depth on nearly everything on my restoration project, and I am loving it!,

But vacuum lines have me beat, beat, beat.

The EGR valve is not actuating, there is no vacuum at the valve. I can trace the tube from rubber to plastic, through a connector and to the back of the battery where there seems to be a few vacuum solenoids.

What the heck do I do know to try and troubleshoot this. The Haynes manual is worthless on this topic..

And advice will be greatly appreciated!

[Gary Lewis]

I think the 1985 EFI system was the same as the 1986 system. The 1986 EGR electrical connections are shown in Section 9 of the 1986 EVTM here: Electrical/1986 EVTM/Electronic Engine Control. And, at the bottom of that section there is an explanation of how the system works.

But, you probably need to pull the codes on the system before troubleshooting to find out what the computer thinks the problem is. Unfortunately I don’t have a how-to for that on my site yet, but maybe one of the others knows where one is?

[ArdWrknTrk]

There should only be vacuum at cruise with the engine up to operating temp, so it's unlikely you will ever get it to open sitting in your driveway.
In fact, a leaking or stuck open egr is one of the first things to check if the engine stalls when returning to idle.

How do you know it isn't functioning as it should?
Is the truck throwing a code?

[ctubutis]

Yeah, begin by pulling codes:

KOEO
CM
KOER

There are 3 sets of codes to be pulled, the first 2 are delivered together in the same test and the KOER test is delivered independently.

There are certain procedures to follow when doing these tests, it's not like today's pug-n-play OBD-II systems.

Here is one write-up explaining how to do it; I had the official Ford documentation up on the 'net someplace at one time but photobucket being what it is....

http://www.therangerstation.com/tech_library/OBD_I.shtml

[Gsmblue]

Ok, thanks for the input so far, here is some more info:

I did pull codes KOEO 84 EGR circuit failure.

As far as I know the EVP sensor is good, I switched for a spare I had on hand and no difference.

The diaphragm in in the EGR moves freely and looks clean from the top- but I have not taken it off yet.

I do not feel any vacuum on the EGR when the engine is warm, or cold, or doing KOEO - but it sounds like this is to be expected.

When in park my idle speed settles to ~800rpm. Which seems high and it is a little lumpy. It used to be ~500rpm. (I had a barrage of issues a few weeks ago when it got cold... hence the new ignition system!) When in gear it drops to ~500rpm and is stable. Does not miss a beat when waiting at the long red light in town.

I did pull KOER codes a while back, but as I had other issues at the time I don't think these are relevant until I get the KOEO 84 sorted. But I guess I should go pull a fresh batch of codes later today.

Thanks for helping!

[PetesPonies]

Attach a vacuum hose o the EGR and suck on it. Do you pull air? if so, the diaphragm is bad. If you feel resistance, look at the valve and see if you can see the inside moving. If so, all is good with the EGR , other than needing a clean possibly. As was stated, no vacuum at idle, so the vacuum may be applied as it should, when it should, but the valve may be bad. Check it.

[vjsimone]

Have you repaired this issue?

Have you put a vacuum gauge on the line leading to the EGR-Valve?

Like someone said, it only operates during higher RPM. (not at idle or at WOT)

There is a solenoid that turns the vacuum to that line off and on.

The vacuum manifold connected to the solenoids is notorious for leaks, which will also give you a higher idle.

[85lebaront2]

If you need any of the control valves for that system I have a complete set of the 4 from a 1986 F150 5.0L. The EGR on those is strange, there are 2 solenoid valves EGR vacuum and EGR vent and they essentially chatter when the EGR is in use 1987 up Ford went to a single duty cycle valve for EGR.

[Gsmblue]

Thanks 85lebaront2!

I have been away for work for a bit so getting caught up with the truck. When I get a chance to look at the EGR again I will probably take you up on this!

[85lebaront2]

Unfortunately they are already spoken for.

[Gsmblue]

No problem, a classic case of snoozing and loosing ! Damn day job getting in the way ;)