Q: 04 Buick Le Sabre. Couple days ago the word volt popped up on the dash.

04 Buick le sabre. Couple days ago it turned off on the freeway, the word volt popped up on the dash. Pulled to the side of the road. Started back up but it started to shake and drive rough. It still accelerated past 30. Still went past 90-100.however during acceleration the check engine light blinks when it goes past 30. Autozone tells me it needs a tune up. Couple days later , I get the full tune up, plugs, wires , and filter. Guy fixing finds out one of the coils is working. We go get another coil. And it still isn't working. So I suggested if it was the ignition control module. And he says it could be. But I don't have the money for it til next payday. Could this be the problem to why I'm not getting over 30. Oh and btw it goes over 40-50 and so on eventually. But it only does this when I let off the gas and tap on it lightly then let off of it and start tapping on the gas again. So back and forth doing that gets it over 50. But I can't do something like that getting on to the f

My car has 194000 miles.
My car has an automatic transmission.