[2000rolla]

today the temperature suddenly dropped by a lot and my engine noises started to get louder

the noise sounds like a rod knock, but i don't think it is. i don't know if oil has anything to do with it, but it's my first time since last summer i putted 10w-30 oil in the car (used 5w-30 during winter)

here's the description:
in the morning i started the car, it turned right over.the knock isn't very noticeable, somewhat of a quiet knock in the back ground. i revved the engine...the engine sound would completely cover the knock, but when i put a screw driver to one of the intake tube, i can still hear the sound. it does seems like that the frequency of the knock increases with the speed. i'm pretty positive that it is coming from the engine, but i couldn't locate which cylinder it's coming from. then when i shifted the gear into reverse (or drive) with the brake pressed the engine is put under load, and the noise become loud and clear. it's like "knock..knock..knock" not very fast knock but rhythmic. during driving, the noise only comes out when the engine is under load ie. accelerating (even the slightest push on the gas makes the noise come out, but the noise completely disappears when i let go of the gas pedal)

when the temperature is hot, the noise would hardly be there. today it dropped close to freezing, the noise stayed for a good while. i don't think it's piston slap, since the noise is still there even when the engine is at full temperature, but it will eventually quiet down after about 5 miles of driving.

the knock sounds almost like a spun bearing, but it only comes out when the engine is under load in cold weather. i recently replaced the exhaust gasket, but i didn't have the exhaust manifold machined. between cylinder 2 and 3 there is a gap between the manifold and the gasket. i could slide a piece of paper in. the gap is only in the area between cylinder 2 and 3 exhaust port. i don't think it's leaking exhaust because the piece of paper will not slide in between the exhaust port and the exhaust tube.

any ideas and suggestions on where i should look for would be much appreciated.

 

[1jzdreamer]

Have you gone through a tank of gas yet? I have had a similar situation and it was just a tank of bad gas. I was the last to fill up at a station that was about to be out of gas, and there was water in the bottom of the tank and it seems thats what I paid for. I drained the tank, and went back to the station, and on the fresh tank "that they gave me for free" no knocking/pinging.

 

[2000rolla]

it's not pinging from detonation

it's definitely a knocking. sounds just like a rod knock, and it's very rhythmic speeds up and slow down with the engine speed, but it only comes out when the engine is under a load (even light load) and fades out if my foot is off the gas pedal. it doesn't sound like the random ping from detonation at all.

 

[toyomoho]

Crank or rod bearing knock would get louder under an engine load.

If you suspect rod knock during that period of time when the noise is loudest unplug each spark plug or remove an injector plug wire. If rod bearing knock the noise will go away as it is no longer under load.

Changing the 10w-30 should not have cause a problem.

Might also be upper drive train noise under the valve cover.

You a section of hose as a stethoscope to localize the noise area.

 

[2000rolla]

Crank or rod bearing knock would get louder under an engine load.

If you suspect rod knock during that period of time when the noise is loudest unplug each spark plug or remove an injector plug wire. If rod bearing knock the noise will go away as it is no longer under load.

Changing the 10w-30 should not have cause a problem.

Might also be upper drive train noise under the valve cover.

You a section of hose as a stethoscope to localize the noise area.

the only reason i suspected it to be something else is that the knock is there all the time until driven for a while. doesn't rod knock occur in a lower rpm range and would be audible even when the engine is idling?

the knock is barely noticeable when idling, unless you press the gas pedal while driving it's hard to tell that anything is wrong with the car. it's kinda hard to do the test you described as the knock only occurs when i'm driving on the road. at idle, i can barely hear anything.

 

[2000rolla]

i drove the car again today. the noise is still very noticeable when the engine is cold

the knock at acceleration is still there when the engine reaches full temperature, but it became a lot quieter and faded into the background

here's the strange thing. after i got home, i shifted the car into park, and revved the engine. it sounds just like a new engine, no noise what's ever. when cruising on the road there's no knock either (unless it's a hill) but as soon as the engine is under load you can hear the knock

what can this be?!?!?!

 

[blb]

i drove the car again today. the noise is still very noticeable when the engine is cold

the knock at acceleration is still there when the engine reaches full temperature, but it became a lot quieter and faded into the background

here's the strange thing. after i got home, i shifted the car into park, and revved the engine. it sounds just like a new engine, no noise what's ever. when cruising on the road there's no knock either (unless it's a hill) but as soon as the engine is under load you can hear the knock

what can this be?!?!?!

Check to make sure the torque converter bolts are tight and report back with what you find.

 

[2000rolla]

Check to make sure the torque converter bolts are tight and report back with what you find.

I'm won't have time to get under the hood until friday.

meanwhile, is it hard to get to the bolt and check it? can you give me some directions?

thanks in advance

i looked on the internet about loose torque converter bolts. the sounds are similar.

 

[huangxin]

wouldn't loose converter bolts become quieter as you put the engine under load?

 

[2000rolla]

well...i got my hopes up for nothing...

pried open the torque converter inspection cover. every bolt on there is tight (didn't have a torque wrench with me, but none of them were moving)

is there anything else that might cause the knocking in my engine?