Hi every 1
I have an evo 8
Mods
Gsc s1cams
Witth normal bolt on and running stock turbo and a tuned

Having idle issue with a 4th cylinder compression at20psi . I changed the plugs, wires, crank and cam sensor, clean and checked the iac, and maf. Did the timing yesterday everything is tdc and still having issues.
Can someone shine some light on my issue plz

 

You are saying that on a compression test Cyl 4 is at 20?? Assuming you performed compression test properly. That's your issue

What are you seeing in the other Cyl's?

 

Cylinder 123 has 170psi and 4 only at 20 psi

 

Did you do a wet test or dry test?

 

sounds to me the rings are shot on cylinder 4 or you have a blown head gasket, how many miles on the car??

 

its at 140,000 i did dry test

 

Do a leak down test so that you can see where the loss is happening. Could be some bent valves. The leak down will help you know.

 

If you do not know what a wet test is, put a cap full of oil in the low cylinder and redo the test and see if the compression goes up... if it does it is your rings, if not then either headgasket or valves or something in the head... which is what a leak down will tell you...

 

Get ready to take the engine apart. Like Freddie said, do a leak down test to help pinpoint the issue. But regardless, it's coming apart. Good luck.

 

Sounds like you have a Subaru lol.

Thats your problem though. Your pretty much running on 4 cylinders. Do a leak down.

 

okay took the head apart broken valve. i guess its time for a rebuild...

 

That's a bummer. Any exciting plans running through your head or just bringing her back?

 

times are bad now just need a car to drive. not sure how bad it is. looks like the spring broke and the valve was stuck down. and the other valve look warp. gonna take it to the machine shop to see how bad it is.

 

ah dam sorry to hear the valve broke on ya, just had a similar compression on cylinder 2 of my little 4 cylinder beater honda, 170 40 170 170, figured the motor was done because i am not tearing it apart, way to old and rusted to be worth my time, so did a little steam cleaning and sea foam through that old carborator and to my surprise got the compression back, the old hunk a junk needed the carbon broken up on those valves and she reseated

running well again so i was gonna suggest the old water and 2k rpms trick to see if you could get the compression back

good luck on the rebuild and keeping the bill down at the machine shop