Coming home last weekend my 1997 blazer starting surging. I could watch the tach going up and down. I made it home and next day change the plugs and cap and rotor. I ran just fine for a couple days and this morning on my way home from work it did it again. Went out there a few minutes ago and its running fine.

I know it can be any number of things. It does it at an idle too so that rules out the transmission slipping. Fuel pump is fairly new......fuel filter hasn't been on there long.

So what i need is ideas of what to start checking. Has anyone else had this problem and did you find out what the cause is?

I forgot to mention the timing chain and distributor have both been replaced.