We have a winner! Started 2 hr drive home and stumbling was getting worse. Stopped at auto parts store, swapped fuel filter and problem completely gone for 100mile drive home at 60-70mph.
Thanks folks! especially @Pighead and @Steamer
Fuel level in the bowl seems "normal" at middle of window sitting still at idle on level ground.
I replaced the fuel pump with OEM sometime in the last 15 years ;)
Fuel tank is brand new (under one week).
Kinda wish i could put a gopro under the hood to see the carb window when it happens
I...
'74 FJ40 original 1.5F, with JimC rebuilt stock carb (rebuild was 15 years ago). FJ60 ignition system.
When driving up hills at sustained high RPM (might be first gear up a steep farm field, or 2nd gear up a steep paved mountain road, the engine starts to stumble. Since highway speeds in 3rd or...