2nd cylinder 96 blazer
 

2nd cylinder on the engine is miss firing i had a shop change the spark plugs and it didn't fix the problem. The shop mechanic told me its got high compression in the. 2nd cylinder. Which i down the road i will put all new cylinders on the blazer. I was wondering could i put some marvel myster oil with my oil to calm down the high compression.

What are the compression values for all 6 cylinders? Have you confirmed the misfire with a scanner and live data/misfire counter?

George

the shop said the 2nd cylinder was higher and the other ones were fine

They didn't give you the values? A certain amount of variation is acceptable.

Did the shop speculate as to why one cylinder has high compression? It can be a number of things such as carbon build up or valve timing. If its carbon then the question is why is that cylinder fouling? Be careful with anything designed to eliminate carbon buildup because that can have unintended consequences on high mileage motors.

George

Blazers are difficult to get a good compression test.

• You need "all" spark plugs to be out.
• You need a battery which is fully charged or/and a battery booster connected so the starter motor speed is the same throughout the testing
• You need the throttle at WOT (wide open throttle - with the fuel injected it normally goes to flood recovery which injects less fuel or none at all.)
• You need a way to make a good seal with the test tool. (I use either a swivel elbow connector or flex hose with a threaded tip and o-ring which screws into the spark plug hole)

Else it's guesswork. Depending on the tool you can not even get a decent seal on the #3, 4 and 5 cylinders.

There is no "too high value on a compression test", except if something is wrong with that piston or combustion chamber. (i.e. different piston in that cylinder). On a compression test, you can determine the sealing of the various cylinders. Also as GeorgeLG said we would need all the measured values. The compression test is a simple manometer which traces a graph for each cylinder. It will show for every cylinder the maximum attained pressure in absolute values (PSI or BAR). The values are relative to each other and depend on how good a seal you can make with the tester tool onto the spark plug hole. Very difficult in a Blazer without an adequate hose and thread in connector.

Once you have all the values you can determine the relative sealing from cylinder to cylinder and with the peak pressure get an overall statement about the health of the sealing. This comes from experience. We know that let's say a 9:1 compression ratio should yield a minimum pressure for a healthy engine of around 10 - 16 bar / 140 - 230 psi. Anything lower than about 9 bar / 120 psi would require a further leak-down test.