hey everyone,

 

i have a 97 legacy gt 2.5 4at.....when im cruising on the highway and the car gets to around 3000-3500rpm....the engine gets really loud then it goes quiet again.....what does that mean....knock sensor?

4 Cylinder Engines have a boom effect. There is a RPM where they suddenly get loud, then get quiet. Its complicated harmonics in the intake and exhaust system.

If this just started look at the intake and exhaust system, make sure nothing is broken or loose. Make sure there are no clogs.

 

nipper

ok.....i just got a k&n filter a little while back maybe thats it

ok.....i just got a k&n filter a little while back maybe thats it

 

BINGO!

 

nipper

so is it a bad thing?

I dont like aftermarket air filters. They can contimnate the sensative electronics by letting much more dirt through then OE, and i consider them a useless expense on a daily driver.

They get more flow by having larger pores, so more dirt gets by. Its even worse if they are oiled filters. This is not good for an engine that gets over 200,000 of life from a stock air filter (subaru has to be doing something right).

Now this is just basic engine physics, not a bad thing, just unacceptable in the NVH that todays drivers demands.

If you want to confirm this, put the old filter back on.

 

nipper

meh i think the rpms shoot up a bit quicker with this filter...it was actually a birthday present im happy with it...i still have to check that knock sensor to see if its cracked

I dont like aftermarket air filters. They can contimnate the sensative electronics by letting much more dirt through then OE, and i consider them a useless expense on a daily driver.

They get more flow by having larger pores, so more dirt gets by. Its even worse if they are oiled filters. This is not good for an engine that gets over 200,000 of life from a stock air filter (subaru has to be doing something right).

Now this is just basic engine physics, not a bad thing, just unacceptable in the NVH that todays drivers demands.

If you want to confirm this, put the old filter back on.

 

nipper

 

I think I killed my old Roo with one I purchased. It was running fine for the longest time...added one of these, then a few months later the head gasket blew. On a 2.2 no less.