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2.5 WRX STI SUDDEN ENGINE KNOCK
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Old 22 Jun 2017, 01:48 PM   #1 (permalink)
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2.5 WRX STI SUDDEN ENGINE KNOCK

I drove to work the other day, everything seemed normal. Started her up for the homeward journey and there was a momentary knocking as the engine kicked in.
I blipped the throttle a couple of times and the engine sounded okay. So I set off. As the engine warmed up, it started to knock again. I could rev up slowly, but when I lifted off, it knocked. Then the management light came on, it went into limp mode, the cruise control and sports lights were flashing.
Basically, it got worse, to the point where I couldn't rev over 2000rpm without it knocking.

Has anyone got any optimistic thoughts?
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Old 23 Jun 2017, 08:30 AM   #2 (permalink)
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Re: 2.5 WRX STI SUDDEN ENGINE KNOCK

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Originally Posted by beejay820 View Post
I drove to work the other day, everything seemed normal. Started her up for the homeward journey and there was a momentary knocking as the engine kicked in.
I blipped the throttle a couple of times and the engine sounded okay. So I set off. As the engine warmed up, it started to knock again. I could rev up slowly, but when I lifted off, it knocked. Then the management light came on, it went into limp mode, the cruise control and sports lights were flashing.
Basically, it got worse, to the point where I couldn't rev over 2000rpm without it knocking.

Has anyone got any optimistic thoughts?
Read the code, its so much easier then the Crystal Ball method lol lol
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Old 23 Jun 2017, 07:54 PM   #3 (permalink)
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Re: 2.5 WRX STI SUDDEN ENGINE KNOCK

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Originally Posted by bugeye_bob View Post
Read the code, its so much easier then the Crystal Ball method lol lol
Hi Bob thank you for your reply.
I had someone with a code reader over to look at the car: It's showing a cam timing error on one bank. The guy said it could be some sort of solenoid gone down which varies the timing, but he's not familiar with new age Subarus.

Someone told me, it's very rare for the timing to go out and it shouldn't knock loudly if it did, do you have any thoughts on that?
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Old 25 Jun 2017, 07:50 AM   #4 (permalink)
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Re: 2.5 WRX STI SUDDEN ENGINE KNOCK

When was the last oil change ?
what was the actual code ?
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Old 26 Jun 2017, 09:13 AM   #5 (permalink)
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Re: 2.5 WRX STI SUDDEN ENGINE KNOCK

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When was the last oil change ?
what was the actual code ?
Hello again Bob.
I don't know if the code had a reference, the guy's diagnostic reader told him there was a cam timing error on a particular bank.

I bought the car about 10 months ago with 28k miles. It's now done 31k and I had the oil changed about 1500 miles/4 months ago.

The engine was quiet, with no rattles or knocks and I average 26 - 27mpg, so I don't thrash it around. I do take it to the limiter sometimes though, otherwise why have one?
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Old 26 Jun 2017, 11:39 AM   #6 (permalink)
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Re: 2.5 WRX STI SUDDEN ENGINE KNOCK

they have filters on the AVCS, these can clog up if oil changes arent frequent.
as an idea of what Im on about.

('03-'05) consensus on removing AVCS filters? - Subaru Forester Owners Forum

This is as long as its not the dreaded bottom end knock ?

get it to a decent code reader, the code is typically stored in historical codes, even if it has been cleared.
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Last edited by bugeye_bob; 26 Jun 2017 at 11:41 AM.
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Old 08 Jul 2017, 10:35 AM   #7 (permalink)
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Re: 2.5 WRX STI SUDDEN ENGINE KNOCK

I was going to take it to Chevron, but I was put off because they told me they would probably use a third party to do the engine rebuild if necessary and I've heard some not good reports about misdiagnosis and very tardy turn around. So I've put it with someone local who's experienced in Subarus and I trust.
However, it seems that diagnosis of the problem is not straight forward. What I don't understand is why this problem set off the engine fault system and was logged as a cam timing error. Also, all crank bearing knocks I've experienced have made themselves evident when the engine is revved up to, say 3000rpm, when under load. My engine knocks after its revved up and the accelerator is released.
I am expecting the worst and I feel the noise is a little heavy to be anything other than rod bearing, but why the cam timing fault? The car has only done 30k and certainly seemed very quiet prior to this. Is there a definitive way of diagnosing big end bearing failure? I'm just a bit loathed to sanction a strip down on a "sounds like" one.
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