Idle circuit keeps clogging up, long.

[mustsurf]

I have a problem I can’t solve. After a freeway run the car won’t idle, starts fine but stalls at idle and surges just off idle.
I can dismantle & clean the carb and she runs fine until I make a few high speed runs. I generally run 20 minutes at 75-80 mph, on the floor up any grades, she runs great until I pull off at the ramp and then she’ll start acting up again.
’71 bug, bone stock 1600 DP, Pict 34, dual vacuum dist., fuel tank replaced before I got her. I have replaced all the fuel lines (genuine VW), installed a filter above the transaxle, and replaced the fuel pump. I am diligent about tune-ups, valve adjustments, timing etc. and she runs great. Until I hit the freeway.
What am I overlooking?
Thanks,
Jim

[Randy in Maine]

Rust in the fuel tank?

[74Pepper]

Have you checked your idle jet? Almost sounds like it is either screwed in too far, or has loosened and is no longer in the "sweet spot". I'd pull it, tap it on the bottom of a can of carb cleaner to be sure there's not crud in it, spray it clean, Spray a little carb clean through the passages that lead out to that jet, re-install. Start the car, let the choke open all the way, then adjust the jet it until it idles just right (looser, not tighter). Use a little blue loctite to keep it in place.

One question; what do you mean by "surging off idle"?
_________________
'66 Beetle, in restoration
'74 Ghia, in restoration
'77 Westfalia Campmobile - Dangit - rear-ended! Now has primer-butt!
Per Gary, A.K.A. "Purple dress girl")

[mustsurf]

74 pepper, When I pull the carb apart & clean the idle circuit she runs perfect for awhile. I have to do this regularly.
The surging is when driving at low speed with the throttle just open a crack, just off idle, the engine is hunting and will not run at a steady speed. It isn’t bucking violently but I can feel it, and it will not idle.

Randy, I got this car from my father in law but he can’t remember exactly when he had the fuel tank replaced. I'll look int this again.