Engine Performance problem
1991 Buick Roadmaster V8 Two Wheel Drive Automatic 201000 miles
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1991 Buick Roadmaster V8: This winter, while driving on 1/4 tank of gas, the engine started running really rough. I pulled over and let it idle for 45 min, occasionally trying to drive (without any luck). After 45 min, the rough engine went away and I was able to get it to a gas station to fill the tank. It drove fine for a week, then when the tank went down to 1/4 tank again I had the same problem.
I've tried HEET and Seafoam in the tank, thinking there was condensation. I've burned through 2 tanks of gas and still have the problem, but it doesn't seem as bad. It's an intermitant problem. It comes and goes. I can drive slowly through the roughness, then after 1/2 hour it goes away.
Am I looking at water in the tank? Fuel pump, fuel injector or fuel filter problem?
It's a 2nd car, and I don't want to sink money into it. Any cheap fixes I should try before I give up?
thanks