-Really- low compression numbers

[Shigun]

According to the guide I saw for checking the compression, I should be getting low 200s. My compression numbers are as followed: (1 - 4, 1 being closest to passenger side) 155 - 150 - 120 - 115

Now, I know I can put some oil into the cylinders to see if their numbers increase possibly, given that its a certain problem, however would that cause an increase of that much? What could possibly have my numbers so low (and varied, in the case of 3 and 4)?

 

[BrokenTsi]

low 200's? what guide are you reading?

Number 1 and 2 are fine. 3 and 4 have problems. Run the car, get it hot, do the compression check with 3 and 4 again and make sure you hold the gas pedal down while cranking. Let me know what you get. I'll wait.

 

[Shigun]

low 200's? what guide are you reading?

Number 1 and 2 are fine. 3 and 4 have problems. Run the car, get it hot, do the compression check with 3 and 4 again and make sure you hold the gas pedal down while cranking. Let me know what you get. I'll wait.

Ya, sorry, I was looking at a guide for a 2G 420a engine and never actually *caught* that part, just the compression test bit. I will have to do the other bit of the compression test tomorrow for you, as it is raining rather rough outside right now.

 

[Talesin]

Yeah, 150 is respectable for the 1G 4g63t. The 2G will read higher, and the N/T will read MUCH higher. And you should never do a compression test cold, unless you're tracking down a running-while-cold issue (like a mis-sealing valve in the morning) and not to check general cylinder health. Drive it around for a good half hour, boost it a bit even. Wear gloves when you take the plugs out, as they'll be pretty hot.

You count the cylinders from the timing belt over. #1 is closest to the driver, #4 is passenger side.

 

[boostnbuds]

and uhh disconnect connect the fuel system to keep from washing out the cylinders that will lower them a bit, not to say you dont have an issue they should still be more even throughout. Do a wet compression test to rule out a piston ring issue.

 

[Talesin]

You pull the MPI relay fusible link on the positive battery cable when you're doing a compression test anyway. MPI relay is what turns on the fuel pump, so no power means no fuel. :b
Still sounds like he just did the comp test cold... don't usually hear of two going low right next to each other with a properly warmed-up comp test, unless it's a bad headgasket allowing a leak between the two.

 

[Shigun]

You pull the MPI relay fusible link on the positive battery cable when you're doing a compression test anyway. MPI relay is what turns on the fuel pump, so no power means no fuel. :b
Still sounds like he just did the comp test cold... don't usually hear of two going low right next to each other with a properly warmed-up comp test, unless it's a bad headgasket allowing a leak between the two.

I tried to do it fairly warm, though it took me several minutes of researching what I needed to disconnect and all, and even then I don't think I disconnected the right things, because I was going on a guide for a 420a engine, which I did not notice until today when I looked back at it.

I will try again tomorrow after work, warm the car up and drive it to the end of the road and back, pushing it a bit to get it warmed up fully, then pull out what I need to and check the compression backwards this time, just to be sure it wasn't a thing of cold numbers.

 

[spyderturbo007]

Here is a compression test walk-thru......With pictures!!

 

[paper_clip_boy]

As long as #1 Cylinder isnt reading 92psi when its hot, your fine . Scary that 111psi was my best reading.

 

[dareisstupid]

3 and 4 are the leanest so if your number don't improve it looks like its the rings. Its better to notice them going bad now then after you put a big turbo and injectors on it and burn them up real bad.