okay so i guess ill start with the fact that i couldnt find this answer anywhere. my first truck was a 1997 Chevy S10 4x4 4.3l. I bought it off a lot, it was fine for a month and then it started sputtering upon acceleration, but when it shifted to 2nd gear (lower RPM) it stopped sputtering. i replaced the fuel lines and the fuel filter. it never stalled or even came close to stalling. i sold it before i could fix the problem.

Now, i have a 1996 GMC Jimmy 4x4 with a 4.3l auto, what baffles me is that im having the same issue with this truck. ive seafoamed properly, cleaned intake and cleaned MAF sensor. it will sputter till the engine gets to normal temp then its more or less fine but still sputters. any ideas?

 

Sounds like it could be a bad cat converter. When was the last time it had a tune up?

 

Well when i bought it off of CL i tuned it up, i say that because the previous owner abused it. thick thick sediment and no coolant in radiator, oil thats hasnt been changed for a while, very dirty air filter etc.. the body has 205k and the engine supposedly has 65k but theres no way to tell. ive replaced everything except transmission fluid but thats not the issue anyway. the previous owner also disconnected the check engine light so if it was bad o2 sensors or anything else, i couldnt tell.

 

Then take it to autozone or wherever and get the codes read. Come back with the codes, not the definitions.

 

Im pretty sure you could still get the codes for the computer even with the light disconnected, As long as there's a wiring harness under your dash you can get codes. and if not what have you lost

 

Fuel pump.

You can test the fuel system by hooking a gauge on the schrader valve on the fuel rail, then starting the truck. Should be 50-65psi give or take 10, key on, then drops like 5-10 after started.

Or to test just the pump:
connecting a gauge where the filter goes, and using the remote pump wire see if it build pressure, then see how long it takes to bleed off. if it bleeds off, or doesn't pressurize quickly, the pump is hosed. don't run the pump long in this config or you can damage it. These system also use a post pump regulator so you can't use the hard numbers from this test.

My thinking is this:
The state you said the vehicle was in when purchased wants me to believe the owner also routinely let the tank go below a 1/4 tank. These pumps are in the tank and are cooled by the gas in the tank. Therefore I propose it is the pump.

 

okay ill do the fuel pump and cat converter and see how it goes ill post results after.

 

Why "do" them without getting the codes read? Get the codes read for free, look them up here or post them & replace/fix what has to be. Why replace things you're guessing at? I'd love a disposable income like that lol.

 

the only code it came up with is 'P0140' do you think the Bank 1 Sensor 2 O2 sensor is responsible for the sputtering? i figured the Fuel filter/pump would be cheap, shot that down pretty fast lol

 

the first O2 sensor can cause issues if it goes bad. If you own a Blazer then RockAuto.com will be your friend.