I hope nobody thinks is too stupid, but I am entirely new to this.
I recently attempted to do a compression test using a cheap gauge I bought on amazon with mixed reviews but its what my wallet could afford.
My car is a 2004 Honda Civic Ex with the D17A1 1.7l engine, each cylinder got a consistent reading of 126psi after around 5 cranks. I read some other threads and they mention getting pressure under 135psi as a bad thing, and recommend such things as adding a minute amount of engine oil to help the pistons seal and doing a "leakdown test."
Since the readings are the same for each cylinder, I'm inclined to think that the pistons are fine, maybe my gauge is cheap and could be incorrect though... I was wondering if anyone with experience with this engine could shed some light on my readings to see if they match up. Maybe explain what a leakdown test is, if that's something I should pursue since I got such low readings?

 

Those do sound low , I bought a used compression gauge for cheap and got 150psi on all 4 , I rented one from napa and got 145 ,160 , 145 and 165 so maybe you should get a " second opinion ". The identical readings may be due to a worn tester . Adding oil to the cylinder will help seal the rings , if results are higher then rings are worn (?) . When I suggested a leak down test at the parts store they loaned a block test that sucks up gases from the radiator and mixes them with a blue fluid , if it turns green or yellow you have combustion gasses mixing with the coolant . Mine stayed blue .

 

Maybe five cranks isn't enough. I suggest you re-test and crank until the gauge stops going up... this could be anywhere between seven and eleven cranks... counting the number of cranks until the gauge needle stops moving. Then, test the remaining cylinders using the same cranking count. If any go up faster before the needle stops moving, you may have to consider the first cylinder you tested may be suspect. Ultimately, you need to test each cylinder using the same cranking count and then compare the values for each cylinder. They should be very close to each other in value... a deviation greater than 20 is bad (from highest to lowest) and any cylinder below 125psi should be considered suspect.

Why do you think that testing the compression of each cylinder was necessary ???

 

Thanks, I'll definitely keep that in mind, I was pretty sure it stopped rising but it won't hurt to test it again, and if it doesn't go higher I'll rent a tester to verify the pressure. There are a couple reasons I was testing it, it might not be the cause but its what I could think of to test, I welcome any suggestions. Sometimes the engine will turn over well but then it sounds like it has difficulty with the initial combustion stage, afterwards its usually fine, I know that could be explained by a faulty fuel pump, I was planning on testing that once I ruled this out. Also there was a moment where my roommate was driving the car and it felt like the power cycles were shuddering, the car wasn't shaking or anything but it felt like regularly the power cycle just wasn't keeping up or something, we stopped the car turned it off and on again and it was fine, hasn't happened since. I went on youtube, and found a quick test you can do, which is to take the oil fill cap off and feel if there's any air flow into or out of the engine block. The video said a slight suction wasn't unusual but I had air puffing out, which made me suspect blowby. In general I don't have anything necessarily concrete to point to just a feeling. I've had the car for the past 25,000 miles and havent done much beyond oil changes and tire rotation, maybe it just needs a tune-up?