May be a cam or crank sensor going marginal. Or a relay.....

 

Does the weather have any kind influence when this happens? May be SP wires or coil.

 

Weather has no impact and hasn't done it all day. BUT, after I did the Hughes kit, for a while, it wouldn't idle right. Sometimes it would cut off when you slowed down to stop. That lasted a few hours, then stopped. Maybe the same thing is happening with this. Possibly the PCM learning how to run with the new plenum setup?

 

It's possible the PCM reset while you were working with the plenum.

 

It's highly likely.... 100% in fact... that the PCM reset if you had the battery disconnected while doing the plenum. (which I sure hope you did....)

Sounds like IAC might be getting a bit lazy. Mine figured it out right away. Never stalled on me. Could try cleaning the throttle body, if you haven't yet.

 

We cleaned EVERYTHING. Used Easy Off and a toothbrush on the plenum and throttle body. Looked like a brand new one. Blew out the intake ports on the heads with compressed air. Cleaned the lifter valley. I mean we cleaned EVERYTHING. It has been damn near perfect all day today. Today, I Seafoamed the engine, changed the oil and flushed the radiator. Just finished, in fact.
Quick run through... new Hughes kit, distributor, rotor, spark plugs, wires, coolant temp sensor, fuel pump assy, and thermostat, since I was already doing the plenum. And get this, when I seafoamed it, I cranked it up, no smoke. Drove it down my driveway (about 200 yards), no smoke. Got to the blacktop and nailed it. Threw a ball of light black smoke about 3 feet in diameter. Drove it bout 3 miles and drove "agressively" as per the bottle directions. No more smoke... Thats one clean 318.

 

FURTHERMORE, why does Hughes send a throttle body gasket with the plenum kit, then tell you not to take off the throttle body, but to remove the throttle body and plenum as a unit?

 

Wait, what? You are looking for something to make sense? Seriously?

There's your first mistake.

I took mine off anyway, and cleaned it to within an inch of its life. It needed it. Badly.....

 

Well, I have found when things make sense and follow logic, issues are easier to work out... Thats why life is so dang hard, I guess. Nothing wants to play by the rules.

 

Finally pulled my IAC and that bad boy was FILTHY. Unfortunately I had a radiator hose give up the ghost on me today, so had to replace that. Took it for a test drive and it tried to run warm on me. Never hit the red but got uncomfortably close. Think I need to burp the system. Need to go do that here shortly after the motor cools down.