I've got an '81 4x4 PU that has been developing a problem over the past few summers and has become too frustrating and I can't figure it out. During the hot days in summer (ie, now) the engine won't idle. I have to keep my foot on the accelorator to keep it running. Even then, it runs real rough and jerks and sputters. It only does it when it warms up. It runs fine when I first crank it unless it's been out in the hot sun all day. Anybody had this problem or know what it is? I could use the help.

 

I just bought an 80 4x4 in California and was driving it back to Washington state last week. Midway through Oregon, the truck lost all power and sputtered sputtered as you described. The temps were in the mid 90s and low 100s. I managed to trace it to an intake manifold leak. I put my hand over the intake on the air cleaner assembly and the truck ran smooth. To get it off the highway, I stuffed the intake with a rag. I'll be towing it back this weekend. You may have a similar thing going on with gaskets and heat.

 

I posted on 4x4wire.com for help on the problem. It was suggested that it's the fuel shutoff solienoid so I did a little research and went out and unplugged it while the truck was running. First, it ran rough and then wouldn't idle. It seems to be the problem, but I'll have to check the vac switch out, too, but I think I might just cut the wires and hardwire it into the key switch so it won't turn off. I just haven't had the time to do any of this to see if this is going to fix it for sure. Hopefully this is it. I'd rather not have to take the intake off.