Old post, but still pertinent. I really like my current scan tool (AutoEnginuity). Run a search for scantool and other related search queries and you should find more than enough information. No need to take this thread off on a tangent.

 

Well after living with the nightmare P0300 missfire for the past 3 months were I changing plug's, wires, Dist cap, rotor button, MAP, check compression and MAF I changed the distributor and my 98 blazer runs great. I've been driving it for over 300 miles with out a missfire.

My problem was during light acceleration and cruising at 1500 to 2000 RPM the engine would missfire. The missfire would clear when I would accelerate. One time it was really bad were I had P0300 and P0420. Several times I just had the P0300.

Things to look for that will point you to change distributor. There was a white powder deposit on all the posts inside dist cap. If you see the white deposit pull dist out and look at the gears. If you see wear simular as the attached photo's change the dist and it should fix your problem.

This is a great website. Would have never thought changing the Distributor would have fixed my missfire condition until after reading postings on this site.

 

Will pulling the distributor mess up the timing? I am having similar problems and have done all of the quick/cheap fixes. I need to know how my gear looks before I can sleep well at night but want to be sure of what I'm getting into.

 

Pulling the distributor will not. Putting it back in incorrectly will though.

 

i think i have the same problem as you bellis61@bellsouth.net ....