J240ZTurbo Posted January 25, 2012 Share Posted January 25, 2012 (edited) Hi guys, well I got a nice low miles 280zxt auto few weeks ago and started playing with, the previous owner told me that it sat for a long time, I put some oil on the cylinders before firing her up, and she did for a minute or two with lots of back firing do to old gas, so I decide to take some of the old stuff to the trash and, got my self some new plugs, filter , a nice fuel rail ect, from here I notice that some of the old injectors where not firing up, so I got new injector. So here is the question , today after a month I decide let me do a compression test on this girl , all cylinders came up to 150-155 with no problem exept for #6 this one came up to 120 . I can tell she sat for a very long time, but does anyone know why this is happening will it fixed by itself once she goes on the road? Please help worry here! Juan Edited January 25, 2012 by J240ZTurbo Quote Link to comment Share on other sites More sharing options...
stravi757 Posted January 25, 2012 Share Posted January 25, 2012 That compression seems too high, I wouldn't be surprised to find excessive carbon buildup on the valves and pistons. As for the 120psi cylinder, did you check the valve clearance on it? Quote Link to comment Share on other sites More sharing options...
NewZed Posted January 25, 2012 Share Posted January 25, 2012 142 psi is the standard. The gauge used can have an effect. Did you do a cold test or fire it up and let it run for a while first? Quote Link to comment Share on other sites More sharing options...
J240ZTurbo Posted January 25, 2012 Author Share Posted January 25, 2012 These numbers are cold test Quote Link to comment Share on other sites More sharing options...
Gollum Posted January 25, 2012 Share Posted January 25, 2012 If the low miles are accurate, then it might not be out of range at all. If it were a 150k motor I'd be curious as to the high results on a cold motor, but not a reason to be concerned about. Test variances are more important than actual numbers in my opinion anyways. I'd be happy with anything between 120-160, but a variance of more than 10% between cylinders would have me searching. Check valve clearance if that checks out, perform a leak down. Then if it seems like there's a leak do the oil squirt test (compression test, add oil into cylinder, check again, compare). Quote Link to comment Share on other sites More sharing options...
beermanpete Posted January 26, 2012 Share Posted January 26, 2012 You said the engine was unused for a long time. The rings could be stuck due to disuse. How much have you actually driven the car (in miles)? It is possible that it will improve after driving for a while (hundreds of miles). Go beat the *%#! out of it and see if it gets better. Quote Link to comment Share on other sites More sharing options...
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