Jerks beetween 30-40 miles and sometimes cuts off, rpm drops all the way down

I have a 2003 Montero Sport a month ago I had a mechanic re do the timing due because they had done the timing belt 6 months prior, and they left the time two notches off causing the timing to be off, and flooding the crankcase, where it died and wouldn't turn on, I didn't pay him, because he did it last, and he looked upset, now a month later, the service engine light went on again, and this time it jerks between 30 40 miles, slightly like as if stepping on the brake, and sometimes not always will cut off, the rpm drops where I thought it died out, but I let it coast a bit and it it fires back up, what is it? did that mechanic sabotage it some how?