1989 k5 zero idle, will not stay running
 

Im about ready to give up on this thing. 1989 K5 5.7L, I have to keep my foot on the gas to start it and if I let off it dies immidiately. I cant even pull it out of my driveway. I bought it running pretty crappy so it didnt just happen. Previous owner said it sat for a year. It would drive a little before but not at all now. It smells a bit gassy when I run it and it puffs white smoke when I rev it up.

So far Ive changed fuel filter, spark wires and plugs, distributor cap, injectors, cut out the cat converter, cleaned IACV, and put many new gaskets throughout the TB. I tried starting it without the ECT sensor but it wont start at all. Im thinking next to replace the EGR valve but Im starting to get discouraged since nothing Im doing is working. Its not throwing any codes.

I did notice on the passenger side valve cover and manifold its super dirty with grime. Driver side is fairly clean. Any input would be super appreciated as Im about to torch this POS.

You can fashion a block off plate for the EGR valve to use for diagnosis. Just make it out of some sheetmetal using the gasket as a template. It is quite possible that the EGR valve is the issue. You've checked almost everything else. A problem with the ECT sensor could be causing it as well.

When I bought mine it had only been driven a handful of times in the two years the guy before me had it and it kind of did the same thing. Not as bad, but I would be driving down the road and it would want to die. I ran some seafoam green and changed the fuel filter (was seriously dirty) by the carb and in no time she was running like a champ.

I hate giving stupid suggestions, but you didn't list this: air filter???

Sounds like a slow IAC to me, I also hate suggesting you throw parts at it, but cleaning the IAC isn't enough sometimes..

The other possibility is someone messed with the minimum idle screw on the TB, but this is very unlikely because usually everybody goes the other way with that screw.

EGR is easy to test. If you can blow through it, it's stuck open. If the vacuum line is drawing vacuum with engine running (causing egr to open), the egr vacuum solenoid is bad (more likely, but not likely!). Otherwise, EGR is fine, doesn't really matter if it's stuck closed..