[STIeffekz]

hopefully someone can help me out with this, its driving me crazy.

well i was driving home from my gfs house last night, when i get home i get outta the car to open the garage door, it was late so it was really quiet out so i could hear every single piece of engine noise. Well as i was walking back to my car i hear a really faint knocking sound from then engine i drive the car into the garage and open up the hood while the car is on.

listening around i could hear a really faint knocking noise like metal on metal making a tap tap tap noise, aside from all the ticking the engine makes, this noise was distinct, it was really faint though, if it was during the day time with all the traffic and all i probably wouldnt even hear the knocking noise unless i listen really carefully.

I got paranoid so i quickly took out my v2 accessport and unmarried the map, after i unmarried the stage 2 91 oct v111 map i reset the ecu by taking off the negative battery terminal and pump the brakes a few times. Then i reload the same stage 2 91 oct map.

after everything i turn the car back on and still hear a knocking noise, only it was even fainter than before...or maybe it was just me.... well anyways i took the car out to drive around the block, and i end up at chevron. i pop the hood at chevron and still hear the knock noise, its really really faint though, when i get closer to where the turbo is i hear it a little better, so it does kinda seem like its comming from the block, again its a really faint knocking sound.

i check oil level and everything and it all seems fine and full. So i drive home. While driving home i decided to give some boost, not a lot, i went from third gear at 3k rpm to 4.5k rpm and let off, so thats barely giving anything, when i get home the knocking sound is still there. Really soft and hard to hear unless you are carefully listening to it. At that point i gave up and called it a night, it was already almost 2 AM, and i decided to just jump on here and see if anyone has opinions.

the car is a 2004 STI with 25,900 miles. mods are full tbe and a cobb ap v2, always filled with chevron 92 octane, and once with shell 92 oct. Oil level is always full and the car doesnt burn any oil at all, always changed with mobil 1 10w30. The only thing i did the other day was switch my intake back to stock, i went from a k&n typhoon intake back to a stock intake with a fram drop in air filter. Hopefully the stock intake isnt the problem, i mean can a intake really cause knock issues?

The car pulls strong and theres no CEL, also i cant hear the knock while driving or if im in the car at a complete stop, only if its really quiet and im standing over the engine bay. Maybe im just paranoid and the noise was always there and is normal but i never took notice of it till now?

Another thing is can gas get old? my car is not a daily driver, i drive maybe 100-150 miles in a month, and since it just sits, can the octane rating start to lower? if it does maybe thats causing the "knocking" issue that i have? and can i jsut solve it by filling it up with some newer gas?

what do you guys think? thanks in advance for any help and the time taken to read this post.

[aoisubaru]

Do you hear it only when the car is idle? Can you hear it when you are driving? Does the knocking sound different depending on what RPM you are at?

[LSE]

I would data log it. just keep in mind our engines are pretty noisy. maybe you can post an audio clip?

[lapinga]

maybe you left a tool when you change the intake

[STIeffekz]

Originally Posted by aoisubaru

Do you hear it only when the car is idle? Can you hear it when you are driving? Does the knocking sound different depending on what RPM you are at?

yes i only hear it at idle, i cant hear it while driving or while im sittin inside the car, only when im over the engine bay and listening really carefully for it

[Tweeter]

Sounds like rod knock or you're just paranoid.

Post up a video clip if you can.

[STIeffekz]

Originally Posted by Tweeter

Sounds like rod knock or you're just paranoid.

Post up a video clip if you can.

i dont think a video clip will do any good, only because the knocking noise is really faint, and it only happens when the engine is at operating temperature with the idle at around 6 - 700

when the engine is cold the rpms are higher making the engine noise higher so i cant hear the knock at all.

its funny though if it is rod knock wouldnt my car feel different at all? like slower or wouldnt it trigger a CEL? i mean the car feels strong and theres no CEL, so what could it be?

can gas lose its octane rating if its been just sitting in the car? i drive the car rarely, and a full tank of gas last me a month, so can that gas thats in my car start to lose its octane rating if its just sitting in the gas tank for so long?

[aoisubaru]

Originally Posted by STIeffekz

yes i only hear it at idle, i cant hear it while driving or while im sittin inside the car, only when im over the engine bay and listening really carefully for it

Well, if its not kicking on CEL and the car is now losing its power, I wouldnt be concerned much, but I can be wrong. It could be something as some rattle from underneath the car. Maybe a heatshield.

[WRX4ME LE 482]

I wouldnt expect rod knock at 25000 miles.

Im guessing something loose, or like somebody said above, a tool was left/dropped off in the engine somewhere.

One thing's for sure. If it's rod knock. Itll get ALOT worse...

[Rootus]

Originally Posted by STIeffekz

knocking noise is really faint, and it only happens when the engine is at operating temperature with the idle at around 6 - 700

Knocking or ticking? If it's a deep knocking sound, that may be worth checking out. If it's higher pitched, more of a tick, it's normal. Or at least, mine has a tick only audible fully warmed up at low idle that's existed since I bought the car, almost 3 years and 50K miles ago. Many track days and miles later, it would be dead by now if it were something bad. These boxer engines make all kinds of little ticks, knocks, and **** like that. On top of that the stock manifold makes the exhaust resonate and cause yet more sounds that are easy to mistake for engine noises when you're feeling a bit paranoid.

its funny though if it is rod knock wouldnt my car feel different at all? like slower or wouldnt it trigger a CEL? i mean the car feels strong and theres no CEL, so what could it be?

If you're worried about bearing knock, listen for it right when the engine fires up, that's where you'll hear it first.

[STIeffekz]

Originally Posted by Rootus

Knocking or ticking? If it's a deep knocking sound, that may be worth checking out. If it's higher pitched, more of a tick, it's normal. Or at least, mine has a tick only audible fully warmed up at low idle that's existed since I bought the car, almost 3 years and 50K miles ago. Many track days and miles later, it would be dead by now if it were something bad. These boxer engines make all kinds of little ticks, knocks, and **** like that. On top of that the stock manifold makes the exhaust resonate and cause yet more sounds that are easy to mistake for engine noises when you're feeling a bit paranoid.

If you're worried about bearing knock, listen for it right when the engine fires up, that's where you'll hear it first.

hmm maybe you guys are right and im just being really paranoid, but does anyone know if gas octane rating starts to lower if its just sitting in the gas tank for lets say a month?

[Rootus]

Originally Posted by STIeffekz

hmm maybe you guys are right and im just being really paranoid, but does anyone know if gas octane rating starts to lower if its just sitting in the gas tank for lets say a month?

A month ain't that long, it's likely just fine. In any case pinging is not something that occurs at idle.

[CGMDan]

engine knock will occur under load. So low rpm high throttle input would cause the most knock. When its bad it sounds like someone threw a bunch of rocks into your motor.
What your describing doesn't sound like engine knock at all.

[Tweeter]

Loose belt maybe.