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Discussion Starter · #1 ·
Hello, I'm a new member here and 2 weeks ago my outback has started knocking. I took it to a shop to check the timing belt tensioner, since it was timing and involved removing the main pully I didn't want to mess with it. I took it back before they kept diagnosing, took it to another shop and the mechanic said strictly based off of the pitch and where it was coming from it was very likely a bad wrist pin. I heard your engine would seize up or lose power if it was a spun bearing. For those 2 weeks the car was running I have been driving the car as it is my only car. I don't feel any loss of power, you can hear it at idle but only really gets noticeable once past 2.5k rpm and holding the rpm speed while driving. Also suddenly gets loud once throttle is let off but goes back to "normal". When driving uphill or downhill, particularly on the highway the knock is completely gone until the road flattens out again. If given a significant amount of throttle no knock can be heard as well. If given full throttle from 5k-redline it knocks a little but not too loud.Does anyone know what this could be? I don't currently have the money for an engine rebuild and it drives perfectly fine other than being noisy. Could I continue to drive it how it is?

Thanks so much in advance
 

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2020 Onyx
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Is there any way for you to post a link to a video of the sound? Both outside with the car stationary and while driving? Without hearing it saying that your engine makes knocking noises is very difficult to think about.

I took it to a shop to check the timing belt tensioner, since it was timing and involved removing the main pully I didn't want to mess with it. I took it back before they kept diagnosing, took it to another shop and the mechanic said strictly based off of the pitch and where it was coming from it was very likely a bad wrist pin.
It's really not clear what happened here. What makes you say it was timing? Did you use a scan tool and found high knock counts? If so have you ruled out false knock?
 

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Did the first shop change the tensioner or no? It sounds like you got the car back before they could check?
 

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If it may be a noisy wrist pin you SHOULD NOT be revving out to red line as if it is indeed a noisy wrist pin, you could grenade your engine!

Until you have an accurate diagnosis you need to drive your vehicle gently especially if you need it to last. An unhealthy engine, if driven gently, can last a very long time.

I would change the engine oil and filter using a quality oil. If your engine is a high mileage engine it would be wise to consider a quality high mileage engine oil as this will give added protection. It may be wise to start doing engine oil changes on the severe schedule which is around every 3,000 miles as this will ensure the engine has good lubrication with little or low contamination of the oil.

There are other possible reasons for knocking in the engine such as a failing rod bearing. If the rod bearings are starved of oil from low oil level or poor quality oil (old oil or cheap oil) then they can get premature wear allowing the two connecting rods on the same crankshaft journal to “knock” against each other. If you run the engine at high revs with failing today bearings you will do more damage.

Seagrass
 

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Discussion Starter · #5 ·
Is there any way for you to post a link to a video of the sound? Both outside with the car stationary and while driving? Without hearing it saying that your engine makes knocking noises is very difficult to think about.



It's really not clear what happened here. What makes you say it was timing? Did you use a scan tool and found high knock counts? If so have you ruled out false knock?
I will try to get a video up as soon as I can. It wasn't the belt tensioner so I took it back. I didn't use scan tool because no CEL but I'll get it scanned tomorrow.
 

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Discussion Starter · #7 ·
If it may be a noisy wrist pin you SHOULD NOT be revving out to red line as if it is indeed a noisy wrist pin, you could grenade your engine!

Until you have an accurate diagnosis you need to drive your vehicle gently especially if you need it to last. An unhealthy engine, if driven gently, can last a very long time.

I would change the engine oil and filter using a quality oil. If your engine is a high mileage engine it would be wise to consider a quality high mileage engine oil as this will give added protection. It may be wise to start doing engine oil changes on the severe schedule which is around every 3,000 miles as this will ensure the engine has good lubrication with little or low contamination of the oil.

There are other possible reasons for knocking in the engine such as a failing rod bearing. If the rod bearings are starved of oil from low oil level or poor quality oil (old oil or cheap oil) then they can get premature wear allowing the two connecting rods on the same crankshaft journal to “knock” against each other. If you run the engine at high revs with failing today bearings you will do more damage.

Seagrass
I did an oil change right away and it looked normal to me. I use royal purple at the moment
 

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That is definitely a knock sadly. You should not Rev it to hard unless it's an emergency. Question now is which cylinder, likely 4, unplug the plug wire or fuel injector connector and see which cylinder causes it to stop(1 at a time).
 

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Discussion Starter · #10 ·
That is definitely a knock sadly. You should not Rev it to hard unless it's an emergency. Question now is which cylinder, likely 4, unplug the plug wire or fuel injector connector and see which cylinder causes it to stop(1 at a time).
So i did try that. I don't know the cylinder numbers but it was definitely one of the driver side ones. I unplugged it, the car bogged but it came back. I did for both of them individually ofc.
 

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Definitely sounds like a rod knock to me.

As I said previously if you drive gently it could/should last quite some time BUT it is a ticking time bomb and it will eventually fail.

I believe Royal Purple is a good choice of oil in this case, keep checking your oil level and replace oil on severe schedule (3,000 miles) and hopefully it will get you to the time that you can afford to fix it.

Seagrass
 
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