My 1986 F150 4.9L 300 6 cyl. acts goofy on hot days like today (96 here in Mlps,MN). It acts as though it is running out of gas. It has a new fuel pump, new carb, 2 fuel tanks. It's a 4 spd stick with Granny low. I don't think it's vapor lock, but it's driving me f&$#ing crazy. I can't figure out why the hell it's doing it. I run both fuel tanks on a regular basis. The filter is fairly new....HHHEEELLLPPP!!!! before I go Nucking futs !
Gabby

 

Get rid of that feedback carb and install a non feedback carb from a 83 or older 300.

 

ok...so what's the difference between the 2 ?

 

I've had two ignition modules go bad on me recently. The second time it was like I was running out of gas..... intermittent, sputter, die, sputter, die, run fine for a while, repeat. It was a heat-related module failure that only happened when hot.

 

I had a 84 f150 300 with the feedback carb and i could never get it to idle or run right.
I swapped the carb of a 79 or 80 300 and it ran like a top. Some people dont have any problems with the feedback carbs, not me. The computer was to slow to react to changes in air fuel ratios. Also check your intake manifold, the bolts are known to loosen up, causing a major vacuum leak.

 

Yeah,the feedback carb can be a pain.Luckily,I haven't had any problems out of mine yet.I do have a major exhaust manifold leak that's gonna need some attention soon though...

Nightrain