Checked compression today. I had idled the truck to let it warm up but then got pulled away and didn't get back until it had cooled down again. I figured it didn't matter since I just wanted to see all cylinders equal. I'm happy to say that all 3 cylinders on the driver's side are 130psi.

So now I have ruled out compression and I have ruled out fuel (since nothing changed when I installed the new CPI, 3 and 5 are still cold).

I thought I ruled out spark but now I'm not so sure. Look at my plugs, they are 1-3-5 from left to right and have maybe 10 miles on them.




You can see the side electrode on 1 actually has some discoloration to it where 3 and 5 look shiny and new.

1 has some nice tan on the insulator tip where 3 has a huge jet black smudge (that goes all the way down) and 5 looks brand new. What would cause that blackness by the way?

You can't really see in the pictures but there is a dark ring around the top of the threads on 1 where 3 and 5 look shiny and new.

Also 3 and 5 seemed to have a wet film on them when I pulled them. I'm guessing that was unburned fuel.

Is it possible that even though my test light was flashing for all cylinders, that the spark is somehow not powerful enough on 3 and 5 to ignite the mixture? I'm about to try another distributor.

 

I know you changed plugs but that usually happens when the resistors are out in the plugs, black smudge can be from dead arking - For me I have never had any luck out of NGK or Champion plugs - From back in the days of running VW Buggy's in the hills the only plugs that held up for us was Bosch - And that's what I run in all my gas burners from mowers to my Morf

 

Strange, I've used their TR55's in my TransAm forever and they've been great. Luck of the draw I guess.

Anyway I swapped plugs around to see if the cold cylinders followed and they didn't. The truck purrs like a kitten! What the hell is going on??

 

Bets corrosion or dirt ect was at seating point or in the plug threads keeping plugs from seating right for the grounding of them ....