2.5L runs rough in third gear. Black smoke

[GoodGrief88]

My 1993 with the 2.5L has been sitting for about two years when we bought it. Changed the oil, fuel and air filter, treated what gas was in the tank and added ten gallons of 93 octane. At first it ran rough and smoked all the time but now after putting maybe five miles on it it's pretty much only running rough once the transmission goes into third gear. That's when I get the black smoke too. Any advice would be greatly appreciated as I really don't want to just throw parts and money at it. Thanks

[EuroTec]

Could be sticky/leaky injectors, running a bit rich. Add some Seafoam gas treatment to the tank and drive it some kore. It just might clear up.
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If it ain't broke, don't fix it!

[GoodGrief88]

I've tried seafoam and 93 octane gas but it's still running rough and what i would say is rich because of the black smoke. Could a bad coolant temperature sensor be telling it that it needs more fuel than it really needs?

[TheOneTrueQuux]

[Abscate]

A compression test to determine what shape the engine is in order.

It could easily be a paperweight and why the car sat.
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[CdnVWJunkie]

Some good advice here.

Impressive feat getting it running after 2 years. I have found that our current rendering of gasoline with ethanol really deteriorates rapidly, not just the fuel but also all the fuel injection components.

Verify all vacuum hoses are in good order.