Loud Knock in Engine but no check engine light is on.

if there is aloud knock try to seeif it comes form a certain area. short out pluge wires by disconnecting them one at a time and see if knock goes away if it does then it's cylinder and it may be a rod bearing knock. or if at top pull a valve cover and look for a cam follower/camshaft problem.

I did pull each plug wire being a old school mechanic, and the knock never went away before reading your post. I will pull the valve cover and see what I find.. I think the noise is coming from the top. The guy I bought the car from brother is a Subaru Tech and said it was a rod knock.. maybe I will get lucky on this car. Thanks, Kdzee

if it's a rod knock it will drop oil pressure at idle or be low

No drop in oil pressure. I pulled the valve covers on both engines and the chain is real super loose on the 2002 Aerio and tight on the SX4. With 104,000 miles it's probably time to change the chain. Luckily their was no damage to the gears or the chain came loose. Now is this tensioner adjustable?

doesn't look like it as it says to move intake cam backwardsto relieve pressure. besides if you get a chain kit a new one should be with it.

Thanks, I will get a timing chain kit and change everything.

I have the timing cover off..I will inspect tomorrow..

I am replying to this old post. Car is still sitting because I have been working on the road. Yes the oil pressure drops at idle and also the knock changes when I pull one of the plug wires off. When I did this test before it was at idle, now I pulled the plug wires off at around 2,000 rpm's

if oil pressure drops and knock changes when plug wire is pulled then it's probably an internal problem like a rod bearing/main or maybe piston. if you pull oil pan and see one of the rods blue or a lot of side play in it that is the one to pull the cap off of as it's probably destroyed or well on it's way. if crank isn't hurt like still very smooth you might get away with just a bearing but normally that isn't the case.

I will drop the oil pan to see what I have. I have another bad 2.0L engine with a upper end problem, if lucky the crank and rods are good. I believe a valve hit a piston on that one. This was a old post, and want to get this Aerio running for the new year, 2015. Thanks for your help, I'm motivated.