I have a 86 GL Hatchback about a couple weeks ago it started lurching in 3rd gear at about 40mph when I would shift into 4th it seemed to smooth out. But now it is getting worse same thing in 3rd now in 4th gear at about 60mph,any ideas what is causing this I replace what I thought was the fuel filter located on the firewall it had 3 hoses one that came in at the top and two on the bottom.