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Low compression help

 
Old 05-14-2019, 10:03 AM
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Default Low compression help

Hey guys just joined the community and bought an s2k. 2005 ap2 with 130k miles for around 10k. The reason why its a little lower is because it has low compression in cylinder 2 and 3. I tested the car before I bought it but as of right now there have been no CEL or any problems. had the test done at ballade in LA which im now told isnt too reputable anymore but nonetheless these are the number
#1: 220
#2: 160
#3: 170
#4: 220
I havent had any problems yet but the car does burn oil. Not super fast by any means but it does. I’ve heard lot of people say compression should be even across all cylinders but ive also heard that bad compression is just bad compression. I need to do a leakdown that I know for sure, but is there anything that could cause this that I should fix before it? In 2015 this car got valves replaced, valve guides, head bolts, head gasket, spark plugs, and a coil pack kit. Its been 4 years and I dont know if that info helps but lemme know. Im new to this community and cars in general and I’d love some input thanks !
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Old 05-14-2019, 11:19 AM
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Based on the paper you show, it's hard to tell what the leakdown numbers are showing. Is that 57% or 5.7% leakdown on #1? Same for #3 - 4.2% or 42%? Looking at the compression for #1, I'm skeptical that references 57% leakdown as it would be unlikely to read 220PSI if that were the case. But if it were 5.7% for 1, then that calls #3 to question as a 4.2% leakdown is quite good and the compression discrepancy doesn't make sense or there was a testing/gauge error.

Either way, I would want to verify and get a baseline for myself. I would personally re-run the compression test just to see what readings you get. If you still see similar compression drops on #2 & #3, then I would do a leakdown after to determine what the issue is. It is very simple and compression gauges are pretty affordable.

Remove the coils/spark plugs. Remove Fuel pump fuse or injector clips. Screw in tester, have an assistant depress the throttle fully, and crank the engine until your gauge tops off. I make a mental note of how many compression cycles it took to top off as a comparison from cylinder to cylinder. I recommend doing the test while the engine is at/near operating temps, but some do it cold. Whatever you choose, just keep in mind the readings may change so for an accurate baseline, keep your testing method the same.

Both your statements are actually correct. We do want to see consistent compression numbers across all cylinders. And low compression is low compression. Gauges have their own variance, unless otherwise calibrated, and your testing altitude, operating temps, etc will change your readings. However in this case, we do see there is a large discrepancy in your numbers which warrants a deeper look.

There are number of things that may affect your compression/leakdown numbers:
1) Ring wear - If you dont have a leakdown tester, a shade tree method is to pour a cap full of oil down the bore and run another compression test - if your number significantly improves, that may indicate ring/bore wear
2) Bore wear/damage - same as above
3) Valve clearance - only way to tell is via leak down or checking to ensure your valve lash is in spec
4) Worn valve or valve seats - leakdown to determine
5) Head gasket issues - you'll likely see oil/coolant mixing issues if this were the case
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Old 05-14-2019, 02:42 PM
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So, ballade fixed low compression 4 years ago, and now ballade measures low compression again, and doesn't have an idea of whats wrong?
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Old 05-14-2019, 04:20 PM
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Only 14K miles since that major fix? Something definitely seems to be missing here.

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