2004-2021 Subaru WRX STI Compression test guide // **EASIEST WAY**

Today we'll be walking through how to do a compression test on a 2009 Subaru WRX STI. This process is the same no matter what year STI you have!
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Netrum & Halvorsen - Shivers

[@loadb5985]

Unplugging the crank sensor is my preferred way of doing vs. the fuel pump fuse

[@Hustler_state]

Did you ever figure out anymore about this? Just curius ive had very similar lower consistnt numbers across all the cylinder on a cold engine, but im getting like puffs of smoke upon a cold start like a bad turbo seal, replaced tubo same, replaced pcv twice, same, all new valves were done and all new pistons and machined seals all of it. So im trying to understand if it was shitty mechanic with the valves or something with the crank case oressure or what.

[@leandropim]

(16 sti) My engine is shaking and i tested the cylinders, the cylinder 2 is low (60psi) but i tested the injector of cylinder 2 and it is leaking, sorry my poor english, but what do you think about the engine, a leaking injector can cause low psi cylinder?

[@SubOptimal_]

sounds like you need a new motor man

[@jorclon]

How bad is the shake?

[@zakiramjan9822]

excessive fuel can wash out the cylinder. That's why it lost compression. Could be the rings or the crosshatch marks are gone.

[@michaelcarter3149]

60 is pretty bad, unfortunately I have that beat on my 04. 30 psi on cylinder 4, all others 120. Just going with a jdm swap and build the old motor if it's still good.

[@thedigitalidiot]

Do you have to floor the accelerator when cranking or is that only for the older stis?

[@jackemarleeyoung]

Its safer to pull the fuel pump fuse and unplug the crank position sensor. Some have had the engine start and redline on occasion by trying to do a flood start.

[@Lumlums]

You know what I got the same numbers with my harbor freight tester and I wonder if it’s the tester showing low??? Or if all my cylinder are low.

[@OldieProductions]

I don’t remember where I bought my tester, I wanna say advance auto parts or one of the larger auto parts stores. I’ve used it on a few Subarus and have had somewhat normal results from most of them. I think this car having such high mileage the numbers make sense.

[@AutoExpectations]

Stock block can hold every bit of 600 whp. 500 safety.

[@thintz]

KNOCK KNOCK WHO'S THERE? iT'S ROD ROD KNOCK

[@smithwrx5910]

spun bearing?!

[@nathanacuna]

Nice dIy, tear down would be a lot of fun!

[@OldieProductions]

Will be coming soon fingers crossed!

[@MichaelPSmith-mp1fk]

What ended up being the verdict? Also, how would you do wet compression test with a boxer?

[@OldieProductions]

@@MichaelPSmith-mp1fk No verdict yet, haven't pulled the engine.

[@BoostedFA]

Fun my ass... its a ringland failure.. time to tear the car apart. 😒

[@OldieProductions]

@@BoostedFA Some of us enjoy doing teardowns and rebuilds. I'm not 100% certain that it's ringland failure in this case, because the car has near perfect compression across the board. If one cylinder had way less or no compression at all that would indicate ringland failure. I'm 99% positive this car has rod bearing failure, hence why it's knocking so loudly.

[@brandonsalas6552]

Simple answer it wasnt taken care of in mechanics eyes maybe speed hungry kid’s opinion of taking care of

[@goatlocker219]

Not necessarily. Our STI's ringlands failed at 69k. It was not modified and only driven by my wife and I and we're both over 40. It's just a terrible engine and there are a number of lawsuits because of it.

[@brandonsalas6552]

Ouch poor thing sounds hurt 🙁