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Hey all. Been here on and off but had to create new account.
Recently bought a 94 Duster with a 2.5 and automatic.

Did a compression test and readings range from 118 to 122psi. Pretty consistent for 108,xxx milea but I'd like to know what the "new" numbers were. I was thinking new would be around 135-140psi. Can anyone help me out? A google search brought me nothing.
 

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Imperial....thanks for that! Lots of great info! I'm still in pretty good shape compression wise. Sadly, no info on the standard measurement when new. Curious how much lower it is now than it was when new, at my current readings.
 

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Ive never had a car where a compression gauge measured 135-140. I think you readings are pretty equal to what you'd get if you went back in time and tested it when new.
 
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I've actually seen compression readings go up, not down from new. Carbon build-up in the combustion chambers will raise compression.
This can vary with fuel quality, past driving habits and general engine health, etc.
If you perform a 'wet' compression test, you could compare the numbers. This is a moot point as you've already established that the engine is within specs and probably healthy.
 

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Good info to know. Being they're all reading close to 120, I wasn't too worried. More curious than anything.
This engine seems to run pretty well and strong when first started but, as it warms up, it develops a worsening miss and was initially worried that a passage may be opening up as the heat rises but a quick 3 switch with the key gave me an O2 sensor code (51, IIRC), so I've ordered one. $22 and change through Rockauto for a Denso unit, $26 and change for a Bosch. $47 at my local parts store!!!! (Don't even remember the brand of that one...LoL)

Thanks again for the assistance!!
 

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If compression was 9.5:1 when new, then you could expect roughly 140 psi, although static and dynamic compression are two different things.
My TBI cars have been about 130 psi at 250K-300K miles.
 

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NEVER use Bosch O2 sensors. They don't work as well - they have 4 longitudinal slits on the sensor, which doesn't allow great sampling depending on where it faces when it stops rotation as you install it. Denso and NGK have 32 circumferential holes, so no matter how it faces, it gets LOTS of sampling.
The other thing is that the Bosch sensor body is 1/8" longer then Denso, and you cannot get an O2 socket over it to unscrew, and still get full bite on the hex at the base. It will then slip and round off the hex, and trap the sensor in the manifold. You won't know when installing it, but when you go to remove it....
 
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