When I start my car cold, around 80% of time I hear this knocking sound under the hood at the end of the start up, but the sound is usually not there if I turn the car off and start again, or the engine is still warm, so sort of a random event, but I definitely notice it more when I start up the car cold. Should I look into this issue?

 

Does it disappear after a few seconds? If so, mine does that and it's from all the oil still being in the pan. It's either the lifters that need to be filled or the dry pistons slapping on the walls, but once you get the oil circulating, it's all good.

 

well, it was a single knocking sound, I don't hear it after the car is running...

 

I'm going to venture out and say you should be worried about having a lemon

 

be concerned, be very concered

 

haha... can you be a bit more specific though, I am cool if it's just sarcasm, but if you guys are serious, I'll need to consider about this, cuz I bought it with 3 k miles on it, so, it's not really out of pic for a lemon...

 

Check your oil level lately?

 

yeah, just did a couple of days ago, both the level and oil appearance looked fine

 

My 3000GT made a knocking sound after starting in the cold sometimes, but it had 130,000 miles and was "out of shape". Sold it before I looked into it but I would be pretty concerned if it was happeneing in a new whip...

 

Mine usually starts with a single knock. Not a clack-clack, just one quick knock on a cold start. Never bothered me much but I noticed it. If it were engine, it would be there and probably get worse with RPM. This is like one quick knock and gone on a cold start. I'm with you. I only have 30K on the car.

 

take it to the stealership or pepboys=]

 

It is the timing chain. The tensioner operates on oil pressure providing force on a small piston, which in turn pushes on the chain, stretching it. When the car sits overnight, the oil leaks out of the tensioner, which relieves the pressure on the tining chain, thus causing a knocking noise when starting the engine until oil pressure builds up, pushing the tensioner and stretching the chain, removing any slack from it. When the car is new, you may not have this condition, however as the engine operates several thousand miles, the timing chain will stretch, allowing it to perhaps come into contact with other parts inside the timing chain cover, until the tentioner stretches it.

 

if you hear a rat-a-tat-a-tat for a few seconds, that's "lifter noise". You should not be hearing that for that long when your engine is cold. My dealer replaced my engine for an OC issue because of this - it was the 1st symptom that led them to start checking my oil at 1,000 mi intervals. agree on checking your oil level - my car did it because it was consuming oil, and even the slightest drop in level caused it to do that on startup cold. I have a 05 G 6mt which is notorious for oil consumption - not sure what you're driving

 

I drive a 07 AT, with only 4 k miles on it, it would be more reasonable if it has like over 80k miles. But yeah, thanks for all the feedbacks, I have officially pulled my G from the road and will take it to the dealership for a check up, along with this annoying grinding noise with the axle (suspect it's a wheel bearing issue, based on some of the posts I've seen so far)... so many problems with this new car... ... maybe I indeed got a lemon?

 

Makes sense about timing chain. I can say my quick knock on start up is "not" a heavy metallic deep sound like a piston, it's not a oil starved lifter sound. Mine is only on initial start up, cold engine and truth be told, it sounds like something under the hood rather than something inside the engine. It's a single knock and nothing repeating and ONLY when the engine first second of the engine when engaging.