I did a compression test yesterday (engine was cold, about 50 degrees to be precise) and found that cylinders 1, 2, and 3 were all right at 215 psi, but #4 was at 230 psi. This is a 7% difference. My question is how do cylinders 1-3 have 15psi lower compression. I personally would have thought it the other way around. My car is a 2002 that I bought with 99,000 miles. I did the oil jet update and a valve adjustment a few thousand miles later (but didn't do a compression test before hand, so I can't really compare it to anything). I wasn't able to get to the #4 intake valves when I did the valve clearance, do you think this could be the cause of this? It's been about 6 months since I did the valve adjustment.

Thanks!
Austin

 

How many times did you check each cylinder? Anyways engine should always be hot and make sure you pull the fuel pump fuse and hold the gas down WOT. Do each cylinder 3 times

 

I did this the same way I've done almost every other compression test: pulled fuel pump fuse, let it turn over 6 times, did each cylinder 3 times and took an average.

I'm not worried about it, I've never seen one cylinder so much higher than the rest. Usually you see one or two a little lower than the others, not ever really any higher. I don't think there is any concern, 215psi and 110,000 miles on the car currently, not too bad.