What my compression test means

[alinski]

Hi-Considering a couple of rather abrupt answers to a similar question I hesitate here but will try anyway. Have an '86 with 2.3L, EFI, 5speed, manual, and 180,000 miles-hope that's enough info.
Today I changed plugs and did a compression test, which I do every couple of years just to ease my mind. Did not disable fuel inj., blocked throttle wide open, warm engine and all 4 plugs had been pulled. I'm just wondering if the following gives anyone enough info to tell me if I should be concerned: results were 175, 160, 155, 185. The 3rd cylinder has been a little low before but in a post here someone said the values should be within 10% of each other! The truck runs just great, almost always has, with no misses. The idle may be a tad rough, but barely off.
Should I worry and what are normal numbers for the test? Thanks

 

[BogusSVO]

with that milage your fine, but 3 is a tad low, and yes you should be with in 10% from Hi to Low

you may want to try doing a wet test.. squrit some oil in the cylider and see if the compression comes up

with #2 bing close to #3 the gasket may be eroding and causing a slight compression leak.

 

[alinski]

Ok, thanks for your help! My manual says 20% but either way it's a little low. You can tell from the age and the mileage that I baby it so hopefully it will be fine for a while. Thanks again.

 

[BogusSVO]

i ment to ask.. to you have some tic from the engine? if so you may have some cam lobe wear if thats it, then the valve will not be open as far and can give lower compression... I have the stock roller cam in all my 2.3

 

[alinski]

Actually I do and have had it for a long time. When the engine is cold, it's noticeable but after it warms up it, usually though not always, disappears. In the past I have added a valve lifter quieter and it helps a lot. I'm not a mechanic of course, can just do minor tune-ups, replace breaks, etc. but I thought it was a sound of worn valve lifters and really couldn't afford to do anything about it until it became worse..

 

[scotts90ranger]

changing the lash adjusters is pretty simple actually, but VERY intimidating the first time, if you do do it grab a ranger roller cam from the junk yard to swap in place of the flat tappet cam you have... the lash adjusters are about $8 each, so it's about $70 to do them all, once you have the valve cover off take a couple pry bars and pry the valves down until you can pull the rockers out one by one, once they're all out remove the locking tab on the back of the rear bearing support by this time you will want to have the timing belt off and the radiator out so you can slide the cam out (no need to take the cam pulley off unless it gets in the way of pulling it out in the truck) then reassemble. if you are this far into it, spend the $12 on a set of valve stem seals, if you are lucky your compression tester will fit your air compressor fittings, a standard valve spring comperssor won't work for these things, you either need the special over head cam spring compressor tool or a couple pry bars with the cam in place... give the spring retainers a wack with a rubber hammer before attempting to get them off to loosen them.

 

[alinski]

Thanks Scott but it's a bit much for me, right now anyway. Maybe one day when I'm feeling brave/stupid, or ambitious I'll give your idea a shot. Thanks for the time spent on the detail!

 

[scotts90ranger]

if it's just a minor tick I wouldn't worry about it too much anyway... and the compression is low, but close enough, it'll run fine for a while.

 

[BogusSVO]

look on the cam lobes for excessive wear, and yess the RR cam would be the way to go.. even being your first time, you can do it in a day.