I have 97 4x4 blazer, It usually runs smooth but awhile back I started it it was shaking with a rough Idle until it warmed up, But even then if I give it light acceleration while in park it starts to shake pretty rough, enough to rattle the insides when It usually doesn't. I changed the plugs, wires, PCV valve and cleaned the EGR valve and MAF sensor and still no change, it does run better. But will still shake if I rev it while in park at about 1 to 2 rpms. Any suggestions? or anyone else with this problem? The truck has 176,000 on it but I bought it off a family friend who took great care of it.

EDIT, I should mention that the morning this happened was on the coldest day of the year, With about a two feet of snow in my unplowed parking lot, I started it, it sputtered and stalled which it'd never done, and since then it shakes. I'm at a loss at how it could start literally overnight. ALSO This AM I accidentally hit my 4x4 on dry pavement, and it wouldn't disengage, I was pulling out of a parking lot and had to drive about 10 miles with the 4x4 chirping the front tires every time I hit a bump. When I could finally park it, I had to disconnect the battery for about an hour to get it to let go of the front tires, Maybe its dry on oil? I asked the guy I bought It from and he'd never added oil or flushed the old oil from the transfer case I guess, Would that make it get stuck?

 

When's the last time you checked/replaced the cap and rotor?

 

I haven't replaced either, and I'm not sure how I would go about checking them

 

Pull it - without removing your spark plug wires. Look inside for excessive buildup, for carbon tracking, for cracks, for the rotor to be excessively worn or discolored...

Really, it's easy and not expensive to replace them with AC Delco parts if you have no idea how long it has been since it's been done.

 

Thanks for the tip, I'll have to try that out, Taking it offs pretty straightforward? And do you think that'd be causing the rough idle? I should mention, That between 1-2 RPMS is when it shakes, but if I revved it to say 3-4 RPM The engine smooths out until it goes back down to 1-2

 

Two screws and it's off. You need to check it to eliminate it, if nothing else.

 

Will definitely look into that tomorrow after work, Thanks for the tips