Many tune up things to consider here but let's look at compression and engine mileage first.
Compression testing the cylinders:
It's really not necessary to know exactly what you should have but 125+ is a good figure to start out w/.
Pull all spark plugs so engine turns freely. Test all cylinders and write down figures. They should vary little unless you have a duff cylinder. Now go back to each cylinder and do a 'wet' test. Spray wd40 or equivalant in that cylinder you are testing only. Connect compression gauge again and write down what you now have. I believe these should be about 125-145 psi. readings for a good engine.
IF:
> the first readings are better than the second ones your rings are bad. By putting that spray of lub. into each cylinder it helps to seal the rings a little better than they are. :o
> The second readings are better then it's your guides and seals are bad.
Your favorite mode of transportation has lost some of its "zip"? You think its time for a tune up and maybe you have had your engine tuned up but it still doesn't have the performance it used to have. Maybe its just a little "slow & nervous" when idling. There are several things that can be the cause: bad spark plugs, bad plug wires, worn distributor, leaking valves, or worn or broken piston rings and the list goes on. Its time for a compression test to determine if you have bad piston rings or leaky valves. The pounds per square inch of compression varies with each engine. If you want to know the compression specs for your vehicle, consult your shop manual. To run a compression test, you need a few basic tools. First and foremost is a compression tester. With your tester, check each cylinder and record the results. There should not be over 20% variance between the highest and lowest reading. If there is a greater variance, you may have internal engine problems. To further isolate the problem, run a "wet compression check". This is done by squirting a some oil in each cylinder (I use about a teaspoon per cylinder). If the compression comes up to specs with the wet check, you have worn or damaged rings and are looking at engine rebuild. :rolleyes: :mad: If the compression doesn't change, you have valve problems and usually can solve your issues with a valve job.
:rolleyes: However, bad valves and worn or damaged rings can be partners. So, when you pull the cylinder heads, check for ring grooves, cylinder cross honing marks and other signs of cylinder/piston damage/wear. You should also consider the mileage on the engine. If it has high mileage, many times a valve job will cause the engine to start using oil. If there is evidence of wear in the cylinders you might want to re-ring the engine as well. The compression test may not help you pinpoint exactly what the problem is, but it will help you narrow down the possibilities. And for that alone, it's worth doing!
I think I got this right, autoshop 101
