Low Compression On One Cylinder

[perdaniel]

Yesterday I did a compression test on my 2001 D4 which has 230.000 km (143.000 miles) on the clock. On cylinders 1,2 and 4 I got between 13.5 kg/cm2 (192 psi) and 14.2 kg/cm2 (202psi), but on cylinder 3 I only got 9.5 kg/cm2 (135 psi). Afterwards I read that you could do a wet compression test by adding oil to the cylinder to determine if the problem was in the valves or in the cylinder itself. I was a bit put off by the amount of oil the web page I was on recommended: 2 ounces. Isn't that 60 cc? That seems a bit much on a high compression engine with less that 500 cc per cylinder. Does anyone here know how much oil I should use on a 1AZ-FSE engine, and if there are known problems with the valves or cylinders in this engine?

[perdaniel]

Never mind, I found the answer in my Haynes manual: 5 ml. Maybe I should have checked there first: facepalm.

[TomdeGuerre]

Let's hope you get no difference with the wet compression test, that way it's likely to be just a valve.

If oil restores the compression reading then it's likely to be the piston rings / cylinder bore worn.

[cmia]

Valve guides..

must be a reason why hes testing compression.. maybe blue smoke.

[perdaniel]

I haven't noticed any blue smoke, but I have had problems with oxygen sensors with failed heater circuits. I have also been wondering if the engine really is producing the 150 PS it is supposed to. It has also been using a little more fuel than think it should. After reading a bit more about compression testing, I am wondering if I let the engine cool to much before performing the compression test (there was some heat left in the engine, but it wasn't exactly hot). I didn't disable the fuel injection either, and from what I have read that may also have influenced the values.

[cmia]

I haven't noticed any blue smoke, but I have had problems with oxygen sensors with failed heater circuits. I have also been wondering if the engine really is producing the 150 PS it is supposed to. It has also been using a little more fuel than think it should. After reading a bit more about compression testing, I am wondering if I let the engine cool to much before performing the compression test (there was some heat left in the engine, but it wasn't exactly hot). I didn't disable the fuel injection either, and from what I have read that may also have influenced the values.

correct..

you will get inconsistent results.

bad mpg..

MAF / o2 sensors

air filters..

stuff like that.,.

[perdaniel]

I haven't noticed any blue smoke, but I have had problems with oxygen sensors with failed heater circuits. I have also been wondering if the engine really is producing the 150 PS it is supposed to. It has also been using a little more fuel than think it should. After reading a bit more about compression testing, I am wondering if I let the engine cool to much before performing the compression test (there was some heat left in the engine, but it wasn't exactly hot). I didn't disable the fuel injection either, and from what I have read that may also have influenced the values.

correct..

you will get inconsistent results.

bad mpg..

MAF / o2 sensors

air filters..

stuff like that.,.

IIRC I don't have a MAF sensor on my car (2001 Avensis with 1AZ-FSE engine), but the heater circuits on the O2 sensors have been failing so often that I have lost count of how many times I have replaced them.

[kazzah Zeph]

😀

[kazzah Zeph]

i also did a compression test on my 1AZ-FE and the result is as follows; cylinder 1, 125psi, 2. 124psi, 3.110psi and 4. 126psi, i need help because my mechanic said the engine is weak though i have no issues with it yet. is it true any body with experience?