Here I go again, 98 blazer 4.3L
almost exactly 2 years ago had same misfire but constant.
This time it happens one day and not the next, or after going out having misfire then when i restart its running smooth.
I did the same replacement as last time that fixed it, plugs wires cap rotor.
This time no change.

I dont know what to do with it being intermittent. Its only the one cylinder and hoping its not a moody injector.

Any and all help would be appreciated, you guys saved me alot in the past 2 years with $$ being on a fixed income.

 

Bueller, Bueller ?

 

Do you notice if the misfire happens when the engine is cold or it's warm? Maybe pull the plug and see what it looks like. Is it black? Is it wet with fuel or oil? What brand of secondary ignition parts did you use. Intermittent problems are tough to diagnose.

 

Sorry been sick. It does it cold and hot. I had to get a duralast cap since that was the best in stock. Bosch platinum plugs, dont remember wire brand.
The plug is a nice tint of brown.

 

Probably the problem right there.

 

Ok so tomorrow the 11th i get my disability check and will get an acdelco cap and rotor that is reccomended.

 

Well replaced the cap and rotor with ac delco ones and no difference. My cheaper parts apparently were working properly.

Now will a faulty injector give a p0305 code or is it just electrical code ?

 

A misfire can be caused by incorrect spark, fuel, air, timing or compression. The trick is narrowing it down to which one it is. I usually recommend starting with a fuel pressure/leakdown test. Use the link below in my signature block and follow Captain Hook's directions. This can help rule out fuel delivery problems with the fuel pump and injectors.

 

Oh yeah, it's probably not timing, so you could probably rule that one out off the bat. Was just stating the things that can cause a misfire.

 

Thank you Rock, I will have to try one by one to find it.
Whats weird to me is that it will be missing then I feel small surges of power, stop for a red light with the miss. Then after going for between half and a mile the next red light its gone and running perfect. Always reads #5 misfire, never another cylinder or even the random misfire code.