1995 3.0 V6 low compression on 5th cylinder

[szfarc]

Hi!

Please, give me some advices what to do.
I have bought 4runner 3.0 V6 with rough idle. The engine has low compression on 5th cylinder (right head, nearest passenger). The compression is 3kg/cm^2 (42psi)
After adding some oil 5kg/cm^2. (71psi)

Car mileage is 130k miles. Mileage is low and i can not believe that the engine is broken. Is it possible ?


I'm not sure what is damaged. Is it possible that the valve is burned ?
Is it possible that the piston or cylinder is worn-out ?

 

[DeclansDaddy]

Could be a lot of things but pretty much sounds like a head removal is in order. If oil makes it jump up I'd say probably not a valve, more of a ring problem. #5&6 cylinders are famous for head gasket problems as well but I don't know if oil would help that. 130k is low but things happen and who knows how it was maintenenced. Best of luck.

 

[Sharpie330]

Need to do a leak down test to find out where is it leaking.

 

[9494runner]

Have exactly the same problem as you, except for the oil improving compression, 85 PSI in Cyl 5, between 125-140 cyls 1,2,3,4,6 . Codes 41 and 52 which is TPS and Knock sensor wire, also lean and rich code(cant remember # off the top) Diagnosis is a burnt valve, dead tps, and knock wire is torched and brittle, she has just a tad bit of suction off the tail pipe.:barf:

engine rebuilt by POS owner, I mean PO, and she was bored out already. My 3.0 is donezo, not worth rebuilding.

Check you coolant level and oil level, color, smell. Fluid on the floor? also if shes burning coolant it will smell. What do your plugs look like, how does she sound (ping knock tick?) has this gotten worse or changed. how is your power? hesitant? what codes do you have, jumping the daig terminals WILL NOT tell you the complete story. at 42 psi you need to rebuild. if you rebuild, DONT SKIMP on replacement parts, do it completely TOP AND BOTTOM if you can afford too, our bottom end usually is rock solid. Pretty sure my PO did not replace valves or anything :smow:. he did timing, heads and gasket, ended up burning a valve and my gasket is still holding great.

3.0 is notorious for burning valves and throwing head gaskets, there are tons of threads about why/how/prevent this in the future

my .02, answering these questions will steer you toward a diagnosis but I am with Sharpie, a leak down test IS DEFF in order, combined with codes and your compression check you should have close to a definitive answer.

 

[mikekfr]

Just 2 pennies but go ahead & replace the head gaskets before you HAVE to replace them, and other stuff to boot. Preventative stuff is good. How about a pic of your 4runner? I never get tired of asking to see other 4runners !!

 

[szfarc]

According to your answers i need to do leak down test. I'm in the middle of gathering parts to do this test.

Please, check if my thinking is correct:
I have air compressor. I need to connect it to spark plug hole and pump pressure into the 5th cylinder. After that i will hear leaking air from the exhaust, throttle or oil filler hole. Am i right ?

For a comparison i measured compression on 6th cylinder and it is about 152psi. I will measure all the cylinders in a few days and share results with you.

I have just bought its car. It is 1995 3.0 V6. It has 130k miles. Coolant had very rusty color. I have replaced coolant and radiator . I do not know if it is connected with my low compression. Sometimes i have got lean and rich code. Engine has very rough idle. It has no power. Engine is not burning oil.

I need to be 100% sure if it is only head removal and regeneration job.

 

[szfarc]

Update!

I have made compression test. According to the factory service manual. Warm engine. All sparks taken off. Battery was fully charged.

Here are the measurements:

Right head:
1cyl - 12.5kg/cm3 (176psi)
3cyl - 12.6kg/cm3 (180psi)
5cyl - 8kg/cm3 (112psi) !!Oil test 8.5kg/cm3 (124psi)!! Insignificant difference within the range of the measurement error.
Rings ok!! :bounce:

Left head:
2cyl 11.6kg/cm3 (165psi)
4cyl 11.6kg/cm3 (165psi)
6cyl 12kg/cm3 (175psi)


Factory values:
Compression pressure:
1.177 kPa (12.0 kgf/cm2, 171 psi)
Minimum pressure:
981 kPa (10.0 kgf/cm2, 142 psi)
Difference between each cylinder:
98 kPa (1.0 kgf/cm2, 14 psi) or less


What do you think about the condition of my motor ?
It has 130k miles on the odometer. Not burning oil or coolant.
I'm not able to do leakage test I must judge according to the compression test and oil in the cylinder test.
Can i be sure that the rings are ok, but the valve or gasket on 5cyl is burned?

I want to rebuild both heads with Toyota parts.

 

[szfarc]

Someone ?

What do you think about the condition of my motor ?

 

[whitetrooper]

Hello,
I like to know what you decided to do with your engine. Did you do a valve job on your engine?
Please let me know

Thank you

 

[AuSeeker]

Hello,
I like to know what you decided to do with your engine. Did you do a valve job on your engine?
Please let me know

Thank you

This topic is 9 years old and according to his profile the OP has been back on the forum in 7 1/2 years, you will not get a reply from him!! :nono: