So for the last 3 weeks my shutoff solenoid took a dump on me so I have been shutting down the truck manually at the pump. Last friday I noticed that the truck took a little more cranking to start, but I didn't think anything of it. Today I just shut off and it "partially" shut down with the key and continued to run very poorly. I shut it off at the pump and restarted the truck and it ran the same like it was on 3 cyls. I gave it gas and the throttle response was non-existant but it eventually just caught up with itself and ran like it normally does, never missing a beat. Theres no smoke at all or drveability issues. What gives? Is my solenoid getting partially stuck or something. I did just fuel up, could a batch of bad fuel be the cause?

 

Could be bad fuel...but I think your FSS is partially closing and cutting off fuel supply. If your are going to continue shutting it down manually then I'd gut the FSS.

 

If you're running a stock fueled truck as your Sig suggests, I'd simply replace the fail(ing) solenoid and be done with it.

It sounds as though the solenoid's plunger is sticking in it's bore. Mine's done that in the past.

Dig around on Ebay for a VW shut-off solenoid (exact same part) and pay a LOT less.

Been there, done that.