Did a compression test numbers BAD.

[nube90]

Hey all, I did a compression test today on my 90 TSi and the numbers were
120-120-120-120 now I know those are very bad but I think my battery is not charging good but anyways my car is burning oil pretty bad thats why I did it I was trying to figure out whats causing it the car smokes basically constantly and there is alot of black soot and oil around the turbo housing any ideas also my spark plugs are pitch black.

 

[andymoraitis]

While your numbers are low, they lead me to ask a few questions:

1. Did you run the comp test on a hot motor?
2. Have you tried a different tester just to be sure it's working properly?
3. When do you burn oil? Acceleration is usually rings and deceleration is usually valve/valve stem seal related.
4. Is your battery so weak that the motor cranks slowly?

Blackness on the plugs indicates a rich condition usually related to boost leaks. If the plugs aren't wet with oil, I wouldn't worry at the moment. Get back to us with more info so we can help you determine where the problem lies and what to do to fix it.

Andy

 

[nube90]

Nope I didnt run it on a hot motor I thought I was suppose to but the Vfaq didnt specify and I did not try a different tester, also im pretty sure it smokes more on acceleration and it wasnt cranking over slow, I had my battery connected to my jeep while it was running to keep juice in it but the car is at my friends house and his grandpa came out and yelled at me. Could it be my turbo seals?

 

[andymoraitis]

Re-run your compression test on a hot motor (drive it around for 10 minutes before testing). If the numbers still seem low, drop a capful of oil in each cylinder and re-test. If the numbers rise dramatically, it means the rings are starting to go and that the bottom end needs a re-build.

Drop us a line with your results,

Andy

 

[nube90]

Thanks for the quick respond ill see if I can get to it tommorow

 

[andymoraitis]

Sure thing. I'm sure some other people chime in once you have fresh numbers.

 

[1997GST]

the wierd thing about his situation is all the numbers are equal. I've had rings go and you'll see some variance in numbers. But solid across the board.. maybe it's a timing issue?

 

[andymoraitis]

If you mean valve timing, that's a good point. I'd re-check the timing marks on the cam gears with the motor at TDC and see if it's off. I still think it's either the tester or rings though since if the cam timing was off, vacuum would be greatly affected and that's something you can easily see on an aftermarket boost gauge (if he has one). The smoking issue is really the tipoff since it happens under boost.

You make a very good point though and it's something else to rule out.

Andy

 

[GVR4592]

Did you do the test at WOT? That will affect the numbers as well.

 

[andymoraitis]

Yup, I've seen a 15 psi difference from not opening the throttle plate during cranking. Good one Luke.

 

[1997GST]

I forgot all about throttle butterfly. You're right, that is like a 15 psi difference. Don't forget to pull the ecu fuse to make sure fuel added to the combustion chamber won't skew the reading.

I had a head gasket go on me a little bit ago on my integra. So I quickly pulled all the plugs and inserted the compression gauge (like normal). The cylinder had water in it so the gauge just filled up with water, coming out the relief valve. Taking apart those gauges I saw where they had a simple desiegn but room for error. There is a copper coil on the inside that flexes with the expansion of compressed gasses. It is possible to have a cheap gauge fail. I'd trust a quality one only.

 

[nube90]

Yes I did test under WOT and the people that owned it before me replaced the T-belt so ill check that out also the car wont idle if that has anything to do with timing but ill check it whenever I get time.

 

[chicagoavenger]

Does it matter if you are at sea leavel or 6k above sea level when you get compression numbers? They say 122 is the service limit on a 1g and but that's at sea level so I am just wondering if that's true and if so what would it be at 5600ft above seal level?

 

[nube90]

hmm im not sure if that matters or not I dont really think so but im pretty high in elavation probably around 4-5k.

 

[robs90tsi]

did you retest? What were your numbers after testing hot?

 

[xveganxcowboyx]

Just a heads up. I've been running just fine on 110-120 compression for quite a long time. Sure it indicates rebuild time, but it's not necessarily the end of the world, especially if the numbers are even.

Also, I retested recently and had one cylinder show 85 without the throttle open (forgot on the first test) and 110 with it open. So I have personally seen a 25psi difference due to throttle plate alone.

 

[nube90]

Yes I retested hot and the numbers were worse like 90 all across but I think the tester might be off or my battery is going dead my money is on the battery.

 

[chicagoavenger]

hmm im not sure if that matters or not I dont really think so but im pretty high in elavation probably around 4-5k.

The reason I ask is because I am at 5400ft above sea level and my number are around what yours where but I forgot to open the tb plate and take out all the plugs. I just wanted to see if someone knew if altitude had an effect on numbers I'm sure they do just not %100 sure

 

[xveganxcowboyx]

The reason I ask is because I am at 5400ft above sea level and my number are around what yours where but I forgot to open the tb plate and take out all the plugs. I just wanted to see if someone knew if altitude had an effect on numbers I'm sure they do just not %100 sure

I've tested my car at 4,500ft and 900ft with little difference in the results. (Less than 5psi and that was after a lot of wear and tear which probably accounts for most of the loss)

 

[chicagoavenger]

I've tested my car at 4,500ft and 900ft with little difference in the results. (Less than 5psi and that was after a lot of wear and tear which probably accounts for most of the loss)

Thank you for real world numbers

 

[nube90]

Well I've figured out its my battery I keep having to jump so I thought I should inspect my battery and sure enough I pick out of the tray and its leaking acid like crazy so get a new battery and a retest.