My blazer has a miss fire when I'm idiling on cyl, 1. I was having problems with cyl, 3,4. I ran a couple bottles of Chevron fuel cleaner and it help them out. Now all of a sudden I have a miss fire on #1. The miss fire is not constant sometimes it is worse than others. I ran some cleaner thru it and it helped a little. Is it time to change the spider injecter for the MFI conversion kit.????????

 

1st off it'll help knowing what you're driving. 2nd I'd check vacuum lines & look under the distributor at the rotor & contacts for fouling etc & look for cracks in the cap. Check spark plug wires & make sure they're not grounding out or close to the block or anything metal.
If it's just on 1 cylinder then I'd look at wires for sure & check the plugs. They should be a greyish brown & a spark tester will tell you if your getting the right spark. If you're not then swap wires if you can & see if it runs better - process of elimination - runs better = bad wire, replace it.

 

It is a 02 blazer with a 4.3 it has new wires,plugs,timing chain, and a completely new distributor. I've had it about 4 months didn't realize all the problems with it. Seems like I'm chasing a ghost

 

I am having the same EXACT issue with my blazer. Its a 96 with the 4.3. First it was the cyl 3,4 misfire so I changed plugs wires cap and rotor ran the fuel injector cleaner threw it too. It only misfires on cyl 1 now and only at idle in drive. Im still trying too figure it out. I am going to check the cap and rotor again today. Yesterday I pulled the plug and wire, they are both fine. Although the plug didnt even look worn at the least, but then again I changed them less than a month ago.

 

have you cleaned out the vents in the distributor? have you checked fuel pressure? can you check the compression? check for intake vacuum? can you pull the plenum and watch for a leaking poppet?, disable ignition and crank over with poppets placed in glass jars. watch each spray pattern for uniformity.

sorry if it sounds like im guessing but all of these are free and are good to check. the cleaner may have removed deposits inside the tank which dont help out already malfunctioning poppets. I know theres a filter but with these injectors, microns matter haha.

 

How many miles are on this beast? An 02 with a new timing chain and new distributor tells me that either it has a million miles, or they were chasing a problem before you bought it. A bad head gasket will also cause a miss at idle. Good Luck!

 

It has 123,000 miles on it also I changed the intake gasket.

 

I have put all the new parts on if since I bought if a few month ago

 

Thats low milage for its age. Im curious why the timing chain and dizzy were swapped out already. Any other history on the motor?