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D.I.Y How to compression test

40K views 71 replies 33 participants last post by  jdm04  
#1 · (Edited)
I searched and the thread I found had all the pictures missing from 05 and yadi so I thought I would post one of my D.I.Y's since most of you who know me know I am a DIY junkie.... ANYWAYS!


First this applies to all cars pretty much... Hondas are just so easy to work on this seems much easier on it!

Here is your starting point.
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First thing is you need to remove the four 10mm bolts holding the spark plug cover on

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Next we'll remove the four 10mm bolts holding down the ignition coils. You will need a 10mm deep socket for that. Then lift the coils and unplug the blue connectors

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Now remove its time to remove the spark plugs. I hate the oring spark plug sockets I recommend buying the magnetic sockets!

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Now keep your plugs in order and compare them... right away I know I'm in trouble as the 3rd cylinder spark plug has liquid on it.... :noes:

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Now you must do one of two things. Depending on the car, you can either pull the fuse for the fuel pump or you can do as I did and pull the injector clips off. Either way you don't want fuel dumping into the engine while testing!

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I don't attach the gauge yet on the tester because it's easier to instal in the cylinder without. But start with cylinder 1. (closest to timing chain/belt) You don't have to start here but I recommend it.

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Now attach the gauge and head into the car.

two thing you need to remember!

a) hold the gas to the floor. You want to test the compression at WOT (wide open throttle)
b) you must be repetitive and bump the engine the same each time for every cylinder!

So hold the gas and crank the engine of 3-5 times. I always do four. However many times you do it just make sure they are all the same! Now go look at your gauge

So here are my cylinders in order

#1
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#2
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#3
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#4
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To my surprise I have not one but two screwed cylinders. You want your cylinders to all be consistent and within a small amount of eachother. As my first two cylinders are.
Compression Pressure:
Above 930 kPa (9.5 kgf/cm , 135 psi)
MaximumVariation:
Within 200 kPa (2.0 kgf/cm , 28 psi)

If you want to test for a ring you can do a wet test now and pour a little oil in the cylinder and test again to see if the compression bumps up.


I hope your engine results don't turn out like mine!!
 
#45 ·
Mostly it tests for bad piston rings. First you want to do the dry test. If it comes back low stick a couple drops of oil in that cylinder for a wet test. If compression bumps up then you have a bad ring started. The oil will fall into the cavity of the leak and bump up compression... Bad sign. If compression stays the same and is low it could be a sign of a bad valve seal or bent valve
 
#51 ·
Base with 60k on it, got it with 52k on it and changed the oil and changed the plugs, the plugs looked pretty burnt and had a bit of oil on them so I changed the valve cover gasket and the spark plug gaskets as suggested by you guys a few months ago.

Checked my plugs a week after putting them in, (2-3 months ago) and they looked dry and carbon fouled but I was told it was ok. Been getting shit gas mileage...17mpg with 50/50 city/highway, so my guess was an o2 sensor...

I decided to do a compression test just to make sure the motor was healthy because cyl 3 looked a little different from the rest when I checked the plugs. Test read 185psi in each cylinder, and the plugs looked REALLY dry carbon fouled...which means the car is running lean... Do you think its just an o2 sensor causing the car to not give the right amount of fuel and my gas mileage? From what I know the most important part of a compression test is uniformity and they were all spot on 185psi so idk ?
 
#53 ·
You sure it was cylinder 3 and not 2 that looked differently? which way are you counting from?

2 will usually look different since it usually gets the hottest due to it being the last to fire and get cooled down with fuel.
 
#54 ·
I did this and got 100, 90,90,95 for the cylinders (1,2,3,4) and for cylinder 2 and 3 I got oil on my spark plugs (not at the tip but around it). Should I be worried :noes:
 
#57 ·
I floored it all the way Im sure.

When you say crank the engine 5 times im assuming let it turn over like 5 times with one turn of the key?
 
#56 ·
Lol. could be his gauge...When i did my comp. test, I used an old gauge I had in the garage of the house....read low number like those...

I was concerned, so I took it to our shop to retest and used the gauge there and was showing 175 -5 on 2 cylinders across.

not saying it's 100% why, but I've had it happen.
 
#58 ·
My engine feels like crap. poor acceleration, and an oil leak. I wanna test this to make sure something isnt seriously wrong, but im worried about what ill find because i dont have a warrenty..fuckin blows...
 
#59 ·
What's the torque spec for spark plugs spaz? Also, where did you get your compression tester. I want to test mine- Had to drive through a few flooded areas last month with my CAI+hydroshield. Car hasn't given me trouble or anything- I coasted through the flooded areas. But, I wanna test to make sure.
 
#65 ·
Try again with a new/different gauge?
Start at the simplest fix, then work your way in. :D
 
#66 ·
decided that after 136,000 miles and being turbo for about 30,000 miles that i should do a comp test. got 235-235-230-235