I did a compression test today on my stock D15 from my 89 Civic DX. It has 210,000 miles on it. Last time I did a compression test about two years ago the numbers were at about 160 across the board...


And today... They were all around 200 PSI!!!????

What's going on? I know that isn't normal... It is a crazy amount of carbon build up? My car seems like it has been running rich for a long time... Could this be the cause? I have a new O2 sensor but I am going to try replacing my coolant temp sensor. I think my car thinks it is cold and runs the cold start injector longer than it should. It is also throwing the injector code which could mean the injector is firing for too long???

Any ideas???

 

was VTEC kicking in?

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by ~sp33~ &raquo;</TD></TR><TR><TD CLASS="quote">was VTEC kicking in?</TD></TR></TABLE>


OMG...buwahahahahahahaa.....i gotta remember that one.....

 

how long were u cranking it?

 

my d15b2 (430,000 kms) had between 180-200 per cyl, so I believe it

my ls/vtec was around 260 per cyl

 

did you do a wet test or a dry test? did you remember to disconnect the fuel pump fuse or relay? cus if your getting higher than before it could be because theres fuel or oil filling in the leaks

 

Uh, the main fuel relay was disconnected. There was some oil in the spark plug tubes though. And that oil probably got into the combustion chamber. Think that could be the reason why?

I need to change my valve cover and spark plug grommets.

 

oh ok. maybe a bunch of oil filled the cylinders but im not sure if all of them would test the same then. when you checkd it was it all the same results between all clyinders?

 

Well like two years ago when I first got the car they all tested at about 160. Give or take like 5 PSI. Which I thought was pretty good for 180,000 miles. Now it has 210,000 miles and it blew like 210, 190, 200, 185 or something like that. They were all pretty close, well within 10% of each other. And I am positive I did the compression test right. I have done it before, etc.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by square_1 &raquo;</TD></TR><TR><TD CLASS="quote">Well like two years ago when I first got the car they all tested at about 160. Give or take like 5 PSI. Which I thought was pretty good for 180,000 miles. Now it has 210,000 miles and it blew like 210, 190, 200, 185 or something like that. They were all pretty close, well within 10% of each other. And I am positive I did the compression test right. I have done it before, etc.</TD></TR></TABLE>

well, good thing is that you've got a healthy motor there

 

I'd bet you got oil in your cyls from leaky spark plug seals. When you removed the plugs, the oil dripped down. Those are wet numbers.

 

It's common for older engines to have very high compression numbers. I did the compression on my 280k D16A6 and it was like 210 on average. In my research I've not found a reason for these high numbers and it certainly doesn't come from carbon build up. There simply isn't enough build up to take up that much volume.

It's possible that leaky valve guides and worn oil rings allow for a small amount of oil to better seal the combustion chamber. ????

Bottom line: your motor is old. The numbers are high because of it. I bet it burns oil like a ****. Either keep feeding it oil or rebuild it. Either way, it's fine.

 

Use some seafoam and then see what it makes

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Boosted Chemist &raquo;</TD></TR><TR><TD CLASS="quote">Use some seafoam and then see what it makes </TD></TR></TABLE>

Exactly what I was thinking.

The #'s were higher due to a build up of carbon.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by glagola1 &raquo;</TD></TR><TR><TD CLASS="quote">It's common for older engines to have very high compression numbers. I did the compression on my 280k D16A6 and it was like 210 on average. In my research I've not found a reason for these high numbers and it certainly doesn't come from carbon build up. There simply isn't enough build up to take up that much volume.

It's possible that leaky valve guides and worn oil rings allow for a small amount of oil to better seal the combustion chamber. ????

Bottom line: your motor is old. The numbers are high because of it. I bet it burns oil like a ****. Either keep feeding it oil or rebuild it. Either way, it's fine.</TD></TR></TABLE>

Sure it is. It's not going to take very much build up at all to reduce the compressed volume by a decent amount.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Boostwerks.com &raquo;</TD></TR><TR><TD CLASS="quote">

The #'s were higher due to a build up of carbon.</TD></TR></TABLE>

wrong.. numbers were higher because of the oil falling in to the combustion chamber.

your either leaking from the spark plug tube seals or the rocker arm assembly o rings.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by janz3n &raquo;</TD></TR><TR><TD CLASS="quote">

wrong.. numbers were higher because of the oil falling in to the combustion chamber.

your either leaking from the spark plug tube seals or the rocker arm assembly o rings. </TD></TR></TABLE>

You know nothing...

 

how so??

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by janz3n &raquo;</TD></TR><TR><TD CLASS="quote">how so??</TD></TR></TABLE>

A poor tuned car (overdue for a tune up) doest burn as clean as it should. Esp something owned by grandma that never saw past 3k rpm. You get a lot of carbon buildup on the piston. So you pistons start getting "more dome" Kinda like high compression pistons. So u run a compression test on a 12:1 motor and the same motor that is stock, you will see a difference. Now use seafoam and it steam cleans the motor and lose the carbon, i bet the numbers will drop again. If any oil was in the chamber due to a leak, most likely it would burn off in some way shape or form (yes there would be some, but minute compared to the amount of carbon that can build up)

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Boosted Chemist &raquo;</TD></TR><TR><TD CLASS="quote">

A poor tuned car (overdue for a tune up) doest burn as clean as it should. Esp something owned by grandma that never saw past 3k rpm. You get a lot of carbon buildup on the piston. So you pistons start getting "more dome" Kinda like high compression pistons. So u run a compression test on a 12:1 motor and the same motor that is stock, you will see a difference. Now use seafoam and it steam cleans the motor and lose the carbon, i bet the numbers will drop again. If any oil was in the chamber due to a leak, most likely it would burn off in some way shape or form (yes there would be some, but minute compared to the amount of carbon that can build up)</TD></TR></TABLE>

Im confused how exactly does oil burn off during a compression test? While you have a valid point with the carbon, its not gonna be that much in there, not enuff to raise the numbers much higher than stock. And even if it is, carbon, with there are times when there is excessive buildup, If the tubeseals are leaking oil and it got in the reading are not true.
As for oil it seals the rings, thats how you test for bad rings if you have a low reading cylinder. You would add some oil to the camber, and test again if the number come up, its bad rings, if they stay the same, its a bad vavle or hole in the piston, etc.... So if the tube seals were leaking and oil got into the chamber when he pulled the plugs, its not a very true reading. And fuel will cause the same thing.

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by janz3n &raquo;</TD></TR><TR><TD CLASS="quote">

wrong.. numbers were higher because of the oil falling in to the combustion chamber.

your either leaking from the spark plug tube seals or the rocker arm assembly o rings. </TD></TR></TABLE>

This man is right on with his answer

 

that depends on how much oil was actually in the spark plug hole. Unless the plug was drowning in oil, I doubt there was enough to make the difference.

facts:
- He claimed the motor was running rich.
- A motor that runs rich for an extended amount of time will have excessive carbon deposits.
- carbon deposits do infact increase compression results.

hence the diagnosis.

 

from my experience iv always had my plugs drenched in oil when i replace them. im just assuming his were too.your supposed to use a teaspoon of oil for the wet test anyways so thats not alot.

Boosted Chemist: i know your right aswell.. but im going by the info iv read and he said there was oil in the tub so when he pulls the plug its gonna go into the cylinder before his test.

 

Same here when mine were leaking they were leaking bad, and i would say that everyone ive seen leak is about the same, its normally enuff to fill the spark plug tube dam near to the top when the boot is in. Im a firm beliver that high results were because of this. Im not ruling out carbon, im just saying the test was wrong, due to the oil, I dont think they would be that even also, if the test was done dry.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by MENACE &raquo;</TD></TR><TR><TD CLASS="quote"> its normally enuff to fill the spark plug tube dam near to the top when the boot is in. </TD></TR></TABLE>

lol wow thats alot more then iv ever had in mine. and just to let everyone know. the rocker assembly o rings are a common problem with these cars. iv read it on michall on demand. most of the time this is why theres oil in the tube.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by MENACE &raquo;</TD></TR><TR><TD CLASS="quote">

Im confused how exactly does oil burn off during a compression test? While you have a valid point with the carbon, its not gonna be that much in there, not enuff to raise the numbers much higher than stock. And even if it is, carbon, with there are times when there is excessive buildup, If the tubeseals are leaking oil and it got in the reading are not true.
As for oil it seals the rings, thats how you test for bad rings if you have a low reading cylinder. You would add some oil to the camber, and test again if the number come up, its bad rings, if they stay the same, its a bad vavle or hole in the piston, etc.... So if the tube seals were leaking and oil got into the chamber when he pulled the plugs, its not a very true reading. And fuel will cause the same thing.

This man is right on with his answer

</TD></TR></TABLE>


Before the test there was no oil, it burns off, during the 4-6 cranks i doubt that much oil would leak into the cylinder.

My truck had so much carbon it bent the gap on spark plugs. Have you ever pulled a head on a motor, or built a motor, if so you would understand.