ok i have a 92 previa and its been running bad so i went looking and so far the only thing i have found is on the dist. on the edge of the signal rotor there are a couple of small burrs. would this cause the van to act like its jumping time? if not what will? it seems to jump time when driving but then it goes back to normal. and when starting it sounds like it tries to fire before the piston is at top dead center. also is running rich. any info would be greatly welcome..thanks