Chasing several gremlins on 350 cu in, 4 spd. Engine runs really rough at idle (sometimes dies). Removed the EGR valve and a hand vacuum pump will not move the diaphragm (open valve). If the valve is sticking "closed" it would not contribute to loss of vacuum-- correct?

 

If it is stuck closed and sealed than it shouldn't affect the idle. It just won't do it's job obviously. I would be looking more at the IAC. That is what controls the idle. My guess is it is totally carboned up. I just took the entire TBI off my 92 and cleaned it inside and out. The difference was night and day. If you don't want to remove the whole thing pull the IAC and make sure the orifice that it screws into isn't gummed up.
Of course I am assuming the truck is tuned and timed properly.

 

It's tuned and timed properly. I kept thinking "vacuum leak", but as yet, have not found any. I'll check the IAC as you suggested. Never thought of that. Hopefully, I'll have time to work on it tomorrow. It's just a farm truck, so does not "have" to be fixed right away.

 

I have also heard those TBI's tend to create a vacum leak from the gasket with some miles on it. Might as well get a new one and clean it while you have it off.

 

Update:
1) Removed TB & cleaned IAC valve/seat. Cleaned entire TB w/carb spray.
2) Sealed EGR valve to manifold using Permatex. Bolts were a bit loose, but no tracking on gasket.
3) Installed new gasket between TB & manifold.
4) Found crud buildup on inside of distributor cap. Cleaned it, but will replace cap in a day or two.

Engine runs much smoother. Hopefully the new ign parts will bring it back to normal.

Tks for all replies.

 

Cool thanks for giving us the results!