1981 E-150 Club Wagon 351w (5.8L) heavily misfiring when warm

[tfarvour]

So, I unhooked the EGR valve and plugged it... the idle problem got a little better, but not by a whole lot. I was able to set the idle down after doing that.. but it will still misfire quite a bit while idling low, and still misfires a few times at high idle. Any thoughts?

[tfarvour]

Ok so... I was playing around some more, and I ripped some stuff out near the air breather to see what was going on. When I plugged the air intake the engine wasn't stalling, this was peculiar, considering most engines would bog out doing this.

Then, I noticed some hoses hooked up to the side of the air filter canister on top the carb. It looks like it hooked up to a smog pump of some type. I took some pictures and when I covered the two holes on this particular item, the idle jumped up and it missed a little less (still missed a bit but definitely not as much?) I know the 5.8 tends to idle a little rough so maybe it's just missing intermittently like that out of age.

Either case... what should I do about this "smog pump"? Should I just plug those two holes permanently?

Also, in the second picture, I took out a silver flex tube that was (for lack of a better term just 'falling off') the black box connected to the end of the breather hose. It looked like it was connectd to an exhaust pipe or manifold of some time... but when I wiggled it around, it was clunking like it wasn't connected to anything at all.. so I just ripped the tube out. It smelled like exhaust pretty bad up front... Thoughts?

[rebocardo]

> I know the 5.8 tends to idle a little rough

It does? When my van is running you can hardly notice it is on except for the exhaust noise.

The silver tube goes to the exhaust manifold and sucks hot air off the manifold. Once the engine is hot, the valve above opens on a vacuum signal and lets cooler air in from the front and diverts the hotter air from the manifold.

That dual port vacuum port probably goes to a set of values and then to the back of the carb. and is attached directly to one of the two charcoal cannisters under the pass. side step. Basically on starting the engine, it sucks the vapors from the can to lessen gas vapors being released to the atmosphere.

The other possible choice is it goes to a bi-metal value on the intake manifold somewhere in the front. In that case you are probably missing a connecting vacuum harness with small check valves like that blue/white one in front of it.

The connector should be shown on the sticker at the front of the van and marked EVP or something like that.

[tfarvour]

Well.. I read what others said it idles rough -- probably incorrect statements.

When those holes are plugged it definitely idles better...and yes rebo, there was a blue/white thing with two vacuum lines plugged in to each other and running down to the charcoal canisters. I unhooked them from the top of the breather canister for the purpose of the photo.

Ok so, do you think the solution might be to just pull everything emissions related? We don't do any inspections here, and the vehicle is pretty old so I'm not too concerned about that stuff.

Where do I start?

I still have a suspicion that there's a blown headgasket. Is a compression test the only way to know?

Thanks guys!

[tfarvour]

Anyone else have any thoughts on where I should go next?

[tfarvour]

I have since sold this van, but I wanted to follow up on the thread (late I know) but it turned out to be a vacuum leak in the carburetor. Rebuilt carburetor and it ran like a champ ever since my last post here until I sold it just a couple weeks ago (Got a new 2008 F-150 now... which also has an issue I'm going to address in another thread )

-Tom