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Compression test results need to be verified
1. is the tester good? Always use 2x testers because one will say 130 the other will say 150
2. did you do the test properly?
A. The engine needs to spin some minimum RPM to create the compression, so Battery need to be full and powerful
B. All plugs out
C. throttle body wide open
D. other factors I probably forgot?
3. test should be done DRY + COLD, then WET + COLD, then HOT and compare
4. Write down the numbers using a decimal, i.e. 130.5, 132.3, 137.9, etc...
5. repeat the test to be sure it went well
6. How many times did you let the engine spin? It typically takes at least 6x revolutions to 10x revolutions (some even number) to get the real final results. One revolution or two won't cut it.
My recommendation is repeat the test under these conditions and use 2x different testers (everything I posted about)
Finally, if you find that the compression is only 130~psi then it means the engine is high mileage, perhaps 200,000+ miles. Otherwise, the cylinder ring and bore was worn prematurely, which I have seen happen to engines where an atmospheric bypass (blow off) valve was used with a maf sensor. When you shift with the atmospheric blow off the maf briefly washes the cylinders down with fuel, ruining the oil film and causing excess wear.
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