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Cylinder 1 down on compression help needed


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Hi guys I’m just looking for a bit of information and guidance. I have a Toyota glanza ep91 and I had a little Rev with my brother thinking he was the kiddie in his Astra gsi turbo he recently bought haha. (Obviously blew him but when I got to the top the hill it started bellowing out blue smoke! (he claims he couldn’t see so he had to slow down) ;-)  well I done a compression test and the 1st cylinder was showing 100psi and the 2nd 3rd and 4th read 130 psi. What I’m wondering is would it b ok to put a new piston and ring in the 1st cylinder or am I just wasting money and better off saving for a rebuild? The car is only running 0.8 bar of boost and the mods it has is front mount intercooler, ct9 hybrid turbo, straight through exhaust with decat and a mines ecu. Any help would be much appreciated. Thanks in advance anthony 

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Yes the car is smoking quite a bit, when I start it up and let it tick over there’s no smoke at all but when you give it a rev it starts smoking quite bad and when you drive it smokes the whole time leaving a cloud of smoke behind you. the smell of the smoke is definitely oil, before I done a compression test I changed the oil stem valve seals but made no difference so that’s why I went and bought a compression tester. The car still pulled like a train and didn’t loose any power at all but it’s in my garage now I can’t use it until it’s sorted and I don’t want to wreck the engine altogether. Do you think it would be ok if I changed the piston and ring or Is it no point? Thanks for the response mate and the crank shaft pulley worked a treat too :-)) 

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19 hours ago, Calum122 said:

These cars tend to smoke anyhow. The compression sounds low, sure, but it's not drastically different from 130 psi.

Is the car smoking loads, or is it only on overrun?

30PSI is a pretty big difference! Defo something wrong. Personally i think changing one piston is a bodge. Buy another known good engine or rebuild it. Did you do the compression test warm with WOT

Edited by Ollieh17
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Just now, Ollieh17 said:

30PSI is a pretty big difference! Defo something wrong. Personally i think changing one piston is a bodge. Buy another known good engine or rebuild it

True, but you're assuming the gauge is accurate and the test was done reliably.

Say there is a deviance of +- 10PSI per test. Then Cylinder 1 may be 110 and cylinder 2 may have been 120. So is a difference of 10PSI massive? 

I'm not claiming to be an expert, but usually when these things go the difference is massive.

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true, but wouldnt you expect a gauge to be consistently inaccurate, so the difference is still relative to each other.There is a chance that the test was done wrong though granted. However even at 130 per cylinder id consider a engine freshen up(unless a reason for low comp)

 

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I done the compression test twice just to make sure and both times it read 100 psi on the 1st cylinder and 130psi on 2nd 3rd and 4th. Yes Ollie I done the test warm so tomorrow I’ll drop a bit of oil through the spark plug hole and see what the test reads then and I’ll take the intercooler pipe off and see if there’s any oil in the pipes. Sorry to be a novice what does WOT mean?? Haha. What could the other causes for low compression be guys? 

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Most likely be rings or ringlands letting blow by, if you are still making 100psi. Which is still too low.

Anything else like melted piston or even a chipped valve, i have found, give 0 psi on a cylinder.

Id say full rebuild.

In theory, if it is just rings then yes you can change them but chances are piston ringlands will have cracks.

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