Chocador

iTrader: (3)

Hi there.
Recently changed the plugs on my 00 type r limited impreza and noted the plugs on cylinders 2/4 (passenger side) were a tad damp,darker brown than the opposite cylinder plugs and fuel could be smelt on them.
After firing it up for the first time in a few months I noticed it still seemed to have a misfire at idle so decided to do a compression test.
I did it stone cold and got exactly 70psi on every cylinder.
I added a few squirts of oil and got 77 psi,I would have expected it to be a lot more.
I do not have a connection to do a leak down test but when holding the pressure in the cylinders the pressure remained stable.
The car has done 69'000 miles,does not use or lose any oil,has roughly 85psi oil pressure,use no water,does not smoke,rattle,knock etc.
Starts on the button and pulls like a train right to the redline so is in rude health.
Possibly I am imagining things as with the boxer engine and large bore exhaust it sounds rough anyway but the plug colour difference and possible misfire have got me and my wallet worried.
So my questions are
1,should the engine be at operating temp when doing a compression test
2,what pressure do you build the individual cylinders up to when doing a leak down test
3,what's the expected cylinder pressure of a good engine-130 psi with a difference of 5% between cylinders?
Just to add the car is mostly standard bar a jap speed decatbexhaust with a subtle magnex silencer.
Any help would be great.ta,lee

crazyspeedfreakz

iTrader: (92)

I'm fairly sure that I read somewhere that engine should be up to temp when
Doing compression test.... I'm sure somone more informed will no but there are plenty
Of threads on compression tests out there...

rob84

iTrader: (5)

usually a hot engine with the throttle open fully

AS Performance

iTrader: (4)

regardless you wouldn't expect to see 70psi.......

suspect as they are all the same its a faulty gauge or you have carried out the test incorrectly??

Chocador

iTrader: (3)

Checked the timing marks and they didn't look right as the marks on the belt were not lining up with anything so timed it up and the marks were not bang on.
Took the tensioner and belt off,timed it up perfect so all marks and marks on belt were bang on,released the tensioner and it pulled the slack out of the belt and moved the crank round so its half a tooth out of time going by the parks on the Crank cog and the mark on the casing under the position sensor.
Not done another compression test yet as I was using a friends gauge,bought myself a kit today and if there's still a drop ill buy a leak down tester.
Pic of mark to follow

SiHethers

On a used belt the marks on belt won't line up with those on pulleys as the belt stretches with use (that's why there's a tensioner). To check cam timing you only need to rotate the engine until crank and cam pulley marks line up (or not if one of cams has jumped a tooth).

I would not use the engine until you can fit a new belt, when reusing an old belt you need to line up pulleys then put new marks on old belt.

Hope this makes sense

Chocador

iTrader: (3)

It is a brand new belt,pulleys and tensioner.
Got it lined up with all timing marks now and when cylinders 2/4 and crank are timed up cylinders 1/3 are out around half a tooth.
Bought a leak tester today so when it arrives ill get some results.

madscoob

iTrader: (3)

clamp the passenger side pulleys before releasing the tensioner, then remove clamp after

Chocador

iTrader: (3)

Once the engine makes 1 full revolution and I line the timing marks up on the crank and cylinders 1/3 then 2/4 will be out as all the slack will be taken up by the tensioner.

merlin24

iTrader: (1)

Quite common to see the cam timing to be half a tooth out - can be due to a number of contributing factors eg pattern belt, crank keyway/crank pulley worn, heads skimmed, block skimmed etc etc.

You also need to rotate the engine clockwise 2 revolutions to bring the timing marks back together.

Mick