i got a 90 eclipse GSX and one of the pistons is not firing... been driving fine and i hopped in it today and its running like ass... i pulled all the plugs and when i pulled the one all the way on the right side (not sure which piston prob 4) there was no change... what do u think the problem could be

 

what do you mean the piston is not firing the pistons job is to create compression the spark plug is the one that does the firing have you diagnosed the problem, check to make sure you got fuel(see if you can hear the fuel pump) make sure you got spark(put the plug on one of the coils and see if the plug creates a spark, maybe a sensor came loose could be a bad coil do the basic checklist first

 

try unpluging the spark plug wires at the spark plugs and putting them on your fingers, while your friend turns it over. That will tell you which plug is not firing!

 

Stick your tongue in the spark plug boot while someone cranks the engine. If it tingles then you don't have an ignition problem.

 

its getting spark to the plug

 

Well if its making compression, that means that at least your spark plug is firing. But you don't have any combustion.

The above tips, sans the finger and the tongue trick, you need to do. Find out which one of your spark plugs isn't firing. It could be a crack in your distributor, bad plug wire or bad plug.

Get cracking and keep us updated.