Horrible compression test results

[phantom_19]

Hi

After smoking at idle and high rpm for about 4 months I decided to buy a compression tester.
For cylinders 1-3-4-2 the results were all about 120 psi the lowest was 118 psi.

When I looked into the spark plug holes I saw that the pistons were covered in carbon or some other kind of black residue.
We have run the car with 880PTE at idle when we started it up, but without tuning in the injectors. Now that we have ECMlink we can.

At my last oil change I smelled a little bit of gasoline.
What is my best bet right now? My dad is on vacation in the USA. Could I ask him to bring stuff so we can fix this?

How would you?

 

[RvlutionMtrsprt]

Did you try pouring a little oil in the cylinders to see if it upped the compression? Might want to perform a leak down test to see where you are losing compression before you try to fix it. It's also quite possible that you don't have anything wrong. I had a car test 100psi across the board on a cold motor with a weak battery. I took a chance and bought it anyway. Put a fresh battery in and got the motor warmed up and it tested 150psi across the board (7.8:1 pistons with 160k miles). Also, are you depressing the gas pedal to wide open throttle while performing the test? Do some more diagnostics before jumping the gun on a rebuild. I would also check the timing to make sure mechanical timing hasn't jumped.

 

[phantom_19]

Did you try pouring a little oil in the cylinders to see if it upped the compression? Might want to perform a leak down test to see where you are losing compression before you try to fix it. It's also quite possible that you don't have anything wrong. I had a car test 100psi across the board on a cold motor with a weak battery. I took a chance and bought it anyway. Put a fresh battery in and got the motor warmed up and it tested 150psi across the board (7.8:1 pistons with 160k miles). Also, are you depressing the gas pedal to wide open throttle while performing the test? Do some more diagnostics before jumping the gun on a rebuild. I would also check the timing to make sure mechanical timing hasn't jumped.

Hi

No it seems I did it wrong. It was a cold start. And I didnt have the throttle open.I will retry but i doubt it will pick up 30 psi.
I unplugged the fuel pump too. Is that also bad?

 

[undefined0000]

Unplugging the fuel pump and full throttle would have the same effect. Full throttle at start-up puts the system in a "drain" mode.

 

[phantom_19]

I just tried all that was recommended. It gave me 120 across the board. What about the carbon build up?
I havent tried adding a drop of oil yet.

 

[My1GLaser]

Excessive carbon build-up will make the compression test higher and give a false indication of the health of the motor. Before I rebuilt my motor 5 years ago, the compression was 155 across the board on a 145k mile stock 6 bolt with cracked ringlands and rings that came out in 3 pieces. Needless to say it was probably reading 30 psi higher than it should have been! I realized this after a complete disassembly. The carbon was thick!!!

 

[phantom_19]

Excessive carbon build-up will make the compression test higher and give a false indication of the health of the motor. Before I rebuilt my motor 5 years ago, the compression was 155 across the board on a 145k mile stock 6 bolt with cracked ringlands and rings that came out in 3 pieces. Needless to say it was probably reading 30 psi higher than it should have been! I realized this after a complete disassembly. The carbon was thick!!!

Then I think the motor was put together really bad. When my dad comes back from vacation in USA i'll tell him the results. Do you think I should ask for him to buy piston rings at Autozone or something?

 

[nickk90]

I'd let the engine warm up all the way and make sure you have the throttle wife opened you would be suprised.

 

[phantom_19]

I'd let the engine warm up all the way and make sure you have the throttle wife opened you would be suprised.

Engine was warm and throttle was open.

 

[Calan]

http://www.dsmtuners.com/forums/articles-engine-fuel/338152-compression-leak-down-testing.html

Is this a new motor? If so, what method did you use to break it in?

 

[WES_393]

I don't think you've done the test wrong, I think it's obvious something is not sealing. Before tearing into the block, run a leak down test. This will tell you what is leaking so you can be better prepared for the repairs.

http://www.dsmtuners.com/forums/articles-engine-fuel/338152-compression-leak-down-testing.html

Edit- Calan beat me to it.

 

[phantom_19]

http://www.dsmtuners.com/forums/articles-engine-fuel/338152-compression-leak-down-testing.html

Is this a new motor? If so, what method did you use to break it in?

The engine has been in the car for 4 years. It went through a blown 14b turbo with oil in the IC system we haven't cleaned it or rebuilt the engine since. We upgraded a few things and started it again. The engine has basically been idling and rev while getting a tune on ECM. We haven't driven it on the street since the 14b blew. Now we have a OEM 16G

 

[BLOHS7844]

Carbon buildup could prevent the valves from fully sealing. Did you ever pour oil in the cylinder like was recommended? That will tell you if your rings are bad

 

[phantom_19]

Carbon buildup could prevent the valves from fully sealing. Did you ever pour oil in the cylinder like was recommended? That will tell you if your rings are bad

I didnt do it yet. On a side note. I do remember the day before yesterday, when I was refilling the coolant that I saw mini bubbles coming up(car running) from the waternek on the engine side, not the radiator. Ill confirm it later on today.
As for the oil, how many drops or teaspoons or whatever should I drop in there.
And is it not strange that all 4 cylinders test 120psi? What could the connection be?

 

[nickk90]

Does it have cams by chance? Aftermarket cams are going to lower the result of a compression test

 

[boost97gst]

Seafoam

 

[curt-s]

Just one teaspoon should be fine.

Just make sure it doesn't settle into the dish of the piston and stay there, otherwise it won't do any good at all except falsely raise your compression because you've now removed some of the open cavity of the dish.

You need to get the oil onto the walls of the cylinder and onto the rings.

 

[RRussell888]

2.4 L mitsubishi galant- OK, here is a real weird one that I need help with - My wife ran the car out of gas and pulled h2o into the fuel system. I added 1.5 gal gas to the tank and 2 bottles of gas h20 remover, I pulled the fuel line from the fuel injector rail/manifold and purged from the tank till no h20. Then we pulled plugs and found oil in the wells, so we replaced the valve cover gaskets, and plug wires. The timing belt and valvetrain looked OK ( as best as you can tell by a visual ) for 120k miles. I couldnt figure out how to purge the h20 downstream of the rail and knew this would contaminate the new plugs. It did, and I figured we would have to change plugs a few times to get it running. We primed directly into two cylinders and it fired but then quit and we couldnt get nothing. We pulled plugs and I had my son crank it and we only have compression on cylinders 1 and 3 ??? HELP