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Selli160

Low Compression rb25

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I’m on my way back from work when all of a sudden it feels like I lose one cylinder. Missfireing like crazy running real rough. I get back home and start trouble shooting what’s going on. Turns out one of my coil packs died but while I had all the spark plugs out I thought I’d give my new compression tester a go. Much to my dismay all 6 cylinders were around 110 psi. (full report below) I don’t believe this to be the cause of the misfire as I’m %99 my coil was munted. But still 110 psi in all 6 cylinders isn’t good. I’ve got a few ideas what could be causing the problem. But any input or ideas would be great. I’m thinking it could be worn piston rings or possibly ringland failure. Although I find it hard to believe the ringland failed on all 6 cylinders.  Also The engine only has 150k on it and is basically stock only thing I’ve done to it is upped the boost from 7 to11psi nothing crazy. But what I think the problem most likely is, is my timing belt is starting to go or skipped a tooth or something and is throwing the timing off and therefore the compression. But hey I’m just some hopeless 18 year old. If any of y’all have the slightest idea what could be going on some guidance would be greatly appreciated.🤘

Rb25det NEO in a rs4s stagea

150xxx kms

C1 105 psi 

C2 110 psi 

C3 107 psi

C4 110 psi

C5 105 psi

C6 117 psi

Edited by Selli160

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Ignore results continue to drive  

 

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Trusting a never-used-before-no-comparative-reference compression tester to give you numerically accurate values is a strong move.

See above advice.

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Increase boost to make up for lack of compression. This always works.

 

Sorry, couldn't help myself. Try different gauge before stressing out.

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Hahaha yeh I’ll see i I can borrow one from somewhere. Still let’s say the gauge works any idea what’s going on?

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24 minutes ago, Selli160 said:

Hahaha yeh I’ll see i I can borrow one from somewhere. Still let’s say the gauge works any idea what’s going on?

Engine is old and worn

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Well turns out you guys were right one of the hoses on the gauge was munted ad was limiting the pressure. But know after fixing it I’m getting 150 psi on all but one cylinder which is at 90psi. So something has f**ked it’s self probably ringland.

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Now you shouldn't trust your technique. There's no way that it would have been ~110 before with a dud tester and now gone down to 90.

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23 minutes ago, GTSBoy said:

Now you shouldn't trust your technique. There's no way that it would have been ~110 before with a dud tester and now gone down to 90.

As above. 
sounds like you are really keen to rebuild this motor!

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You will know, I mean know if you have permanently dropped a cylinder.

Anyway the options are:

1) Rebuild the motor
2) Enjoy motor until 1)

So...

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19 hours ago, Ben C34 said:

Ignore results continue to drive  

 

I second this notion. When my last 2.6 started to drop compression I turned up the boost... Thing ran for another 80,000kms till I sold it.

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1 hour ago, Selli160 said:

or get ready to rebuild the engine

No.....go back and read what I said. I find it very difficult to believe that your results are consistent. Try again before making any decisions. Also, a leakdown test is more informative than simple compression testing.

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