I have an '01 CRV LX (B20Z) 265,000 miles with low compression on cylinder #1. Compression is only 50 psi and leakdown test show 60% leakage on cylinder #1. Check engine code show P0300, P0301,P0303. When I send compressed air down the cylinder #1 spark plug hole I feel air coming out of the exhaust pipe. Before I remove the cylinder head to service the valve, I was wondering how can I diagnose if there are problems with the bottom of the engine like the piston rings. Is feeling for air coming out of the top of the dipstick tube a good diagnosis of low compression due to bad rings for this engine?

 

I don't know about the dipstick tube causing low compression but I do know a somewhat common problem with these 1st gens is the dipstick tub separating from the bottom part. It happened to my 2001 EX just the other day. I pulled the dipstick out to check the oil and the tube came out with it! After a quick search I learned to take off the exhaust manifold cover and press the tube back on. I had to drive less than a mile from the gas station where this happened and when I got home there was oil everywhere. The fix itself was super easy. Good luck.

 

It sounds like you have a bad valve. Perform a leak down test. Google a how to video. You can rent the tester from an auto parts store