MX-3.com

Posted: **February 4th, 2005, 4:41 pm**

How does 30 bucks sound for a compression test? What #'s should I be looking for?

Posted: **February 4th, 2005, 4:43 pm**

$30 isnt bad.. heck if you lived near me I would do it for free for you.. got the gauge.. there is a section in the online manual that I found that tells you the procedure and what min/max results to expect.

Tunes67

Posted: **February 4th, 2005, 4:45 pm**

cool, but isn't the manual for the DOHC 1.6, I have the SOHC 1.6, would the #'s be different?

Posted: **February 4th, 2005, 4:48 pm**

Sorry man.. I dont know that much to tell you for certain.. I do know that compression ratio for the 1.6L DOHC is 9.40:1 So if you know what your compression ratio is supposed to be and its the same as the DOHC.. I would think then the specifications would be the same.

Tunes67

Posted: **February 4th, 2005, 7:04 pm**

do it yourself.. the compression tester itself is like 30 bux.

Posted: **February 4th, 2005, 7:30 pm**

I agree.. all you have to do is unplug the distributor and take out the spark plugs.. then just go down the line one cylinder at a time. Have a buddy crank it for you while you watch the gauge.. even readings that arent super high are ok as long as the readings are relatively close across all cylinders.

Tunes67

Posted: **February 4th, 2005, 8:56 pm**

Yeah i do a monthly compression check on my engine just to make sure my engines health stays good. I have a 30K mile BP in my mx-3 i consistantly have 155psi per cyl. I've heard that the SOHC B6's should have around 180psi at it's best. Not 100% positive though.

Posted: **February 4th, 2005, 10:27 pm**

yep the b6-me should have around 185psi

Posted: **February 5th, 2005, 1:35 am**

thanks guys, I will look into this this weekend!

Posted: **February 6th, 2005, 1:38 am**

Well I did a compression test on my 1.6L today.. and I did not find good news.. hope you had better luck with yours LOL I found 183/181/40/180 across my cylinders.. This definately explains my rough idle.. not sure what caused it though.. my distributor is definately worn.. its having troubles firing #3 cylinder (the one showing 40psi) and its a bit weak on #1 cylinder as well.. 2 & 4 seem to be firing fine.. Funny thing is.. this little car is still pretty peppy.. cant wait to see what it runs like when its firing 100%. Apparently the distributor sends a signal to the ECM which in turn tells the injector to pump fuel into the cylinder.. cant tell from the manual if that distributor signal can effect how much or how long the ECM tells the injector to pump though. Just kind of wondering if the worn distributor could have lead to the apparent stuck valve I have now in #3 Cylinder. Any thoughts guys?

Tunes67

Posted: **February 6th, 2005, 2:39 am**

Compression testers are on ebay pretty cheap.

Posted: **February 6th, 2005, 8:05 pm**

tuunes! sounds like what just happen to me!! I had 184,180,60,189..across my cylinders.. the idle problems is because the cylinder will not fire at low RPM because of the low comprestion but when running around 2000rpm it does!! umm you likey have a burned Valve!! thats what mine was I put a hole new head on and the car works like new!! and now I get 200km per 1/4 tank of gas!

Posted: **February 7th, 2005, 2:42 am**

the idle problems is because the cylinder will not fire at low RPM because of the low comprestion but when running around 2000rpm it does!! umm you likey have a burned Valve!!]

Yeah thats the conclusion I came to as well.. thing is.. I need to figure out what caused this condition in the first place. I can get the head work done cheap or free (disassembly & reassembly will be the spendy part) and I plan to replace the distributor at the same time. But could the distributors worn condition have led to a burned valve? The injector on # 3 doesnt seem to be in bad shape and it appears to be firing normally. So.. what caused the valve to stick and or burn? Basically I want to make sure I correct the cause and not just cure the effect or I might end up in the same situation down the road in the future.

Tunes67

Posted: **February 7th, 2005, 1:08 pm**

i'm going to try to squeez in a compression test sometime this week, so i'll let you know the #'s. I don't have anyone to help me with my car, so im just gonna pay the 30 bucks and have it done

Posted: **February 7th, 2005, 9:44 pm**

I did some reseach into it a little and what I found was there are 2 reason that the valve burns and the 1st is use of low octane gas (87)!! causes the valves to run hotter then with High Octane gas (91) and the other reason is normaly its the number 3 cyclender or the number 2 because they are in the middle of the engine and run a bit hotter because of that!! I noticed when I took off my head that the other valves started to burn but mostly the 2 middle cylenders! its just that my one valve was burned so bad that the compresstion was being lost!. thats likey just because the valve was made not as well as the others. mind you I had about 500,000km on my engine before this happen!

if it was an injector or something it would not burn as hot beacuse when the injectors get dirty it cause them to not fire in a mist.. and that causes not as hot of an ingion in that cyclender so I would rule that out!! but I know its comman on the mazda engine's to burn off valves easy. the other thing is that if there is no back presuse that can cause the valves to burn but you would see that on all the valves! but if you have over 200,000km on it its not uncomman!