240sx with low compression rating!
Posted 8/28/08
well my bud just bought a 89 240sx, he called me over to check it out. i did a compression test. well the psi test came out to be
120, in cylinder 1, 130 in cylinder2, 120 in cylinder3 and, 130 in cylinder 4. i havnt seen so slow ratings, so my thoughts are.

1.valves are shit.

2. pistons are going bad,

3.ring/worn cylinder problem.

any takes on what could be. plzz no smart ass reply's, this for the people that might know a few things. thanks
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26 / M / SoCal
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Posted 8/28/08
buy a honda. problem solved. how many miles r on the engine?
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Posted 8/28/08 , edited 8/28/08
Sounds like worn out rings to me. How many miles are on the car. And pistons dont wear out to affect compression. You really truly have to do a leakdown test to find out.

Pour a cap full of oil in each cylinder and see if compression comes up dramatically. If not than its the seats.
Posted 8/28/08 , edited 8/28/08
the motor has or should i say it reads just about a lil more than 100k, but it might be more cause the cluster was changed to a none-electrical one, but i did pour down some oil before starting it up. still reads 120-130psi
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Posted 8/28/08
What procedure did you use when testing the compression. In my experience the KA24 is a very stout motor, unless is was severely mistreated, there is no reason it should have compression that low. There is a very specific way compression must be tested, if you don't do everything is a specific fashion, your numbers will be off.

Was the engine at operating temp when the test was performed?

Were all 4 or the spark plugs removed during the test?

Was the throttle being held wide open while the engine was being cranked?

If any one of those steps was skipped while you were performing the test, your numbers could be greatly skewed.
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Posted 8/29/08
Pulling the plugs doesnt really matter as much to make a real difference in the numbers. If you've tried oil than it should just be the valve seats. If oil did nothing than the next culprit is your valve not sealing 100%. Really doing a leakdown test will give you your correct answer. HG's are sometimes in the equation but most of the time not really. But when doing the compression you must have the throttle body open.

If your original cluster was changed than thats a clear indication that you cannot trust the miles it says on there.
Posted 8/29/08
No personal threads please...I would advise you to start a more general Car help thread where people can post there problems and queries for other people to answer =]

~locked
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