Strange problem w/93 Jimmy 4x4

Hello everyone, good morning. Been browsing your forum for a bit now, this is my fisrt post.

I have a '93 Jimmy 4.3L Vortec (my winter car) recently purchased 2 mos. ago. I've noticed when i fill my tank with 87 (cheap gas) my car runs rough, like it wants to stall. However when i get to half a tank, it smooths out, no hesitation, idles fine. I've already given it a basic tune up (except i couldn't remove the distributor rotor though, it seemed to be stuck) and replaced the water pump and hoses, due to leak. Does anyone have any suggestions as to what my issue could be with the hesitation?? Is it just that it doesn't like cheap gas, or do i have a fuel line/pump issue??

And no, it doesn't smell like gas in the cabin, or rotten eggs, nor does it ommit any black smoke when accelarating. Thanks for your time.

Pull that rotor button with a channel lock pliers. They get a light rust film under them and fit tight. Sometimes you have to crush part of the old rotor button to get it off. Just make sure you get all the pieces out.

Thanks troubles789

See if there are any screws holding the rotor down.

Other than that, you need to replace the fuel filter and check inside the upper plenum for the injector leaking.

There are no screws holding the rotor down on a 93 dist.

Thank you both for your feed back, i'll take it apart again this week and see how it goes.

Trust me I own a 93 jimmy too. No screws in that rotor button.

95 (with side post mount) and up use a scre down rotor

this is my winter car, so i'm not very familiar with it, the guy who owned it was a mechanic himself, and he tweaked up the engine amongst other things. so everything is trial and error at this point. I guzzles gas big time, do yours do as well??

I get about 20 local and 23 hwy

i'm getting less right, could be do to the fact this guy put in a K&N filter system and the casing to the air filter isn't shutting tight

I get about 20 local and 23 hwy

I am close to that, 19mpg city / 24mpg highway now.

What grade fuel do you fill up on??

87, no point putting anything higher into a 4.3L.

Waste of money. Our engines are tuned for 87.

Really, good to know then.