When I start the car, I hear and feel a knock somewhere in the back of the engine or in the exhaust. Took it to a mechanic, he got it up in the air and couldn't find anything wrong. Everything is tight and he said it might be the torque of the engine doing it. I have an 03.5 6mt; is this a common problem?

 

I have the same issue, and i have an 03 5at..I havent had it checked out yet, so im wondering too

 

there is a tsb for ticking, thumping or knocking noise from the engine. it covers 03-06 both coupe and sedan. (ITB06-012) It states the noise is coming from the fuel damper hose which is on the passenger side of the motor. I would start it up with the hood up and check to see if the noise is coming from there. Of course there are many things the noise could be coming from but stay away from a mechanic that says the torque is making the noise. You can download the bulletin from infinitihelp.com Just register and you can download 1 per day. Does the noise go away when driving or at a certain rpm?

 

wow i just noticed mines doing this too, sounds almost like the engines hitting the hood when it first starts up

 

I only notice it on start-up, other than that i never hear it. I see this must be a common problem.

 

Actually there's no noise to speak of; speaking in idiot terms, it feels like the exhaust is hitting the area underneath the pedals. The idea that it is torque-related actually makes sense; it's just one knock right when the engine starts. Something must be loose, but I can't figure out what it is.

 

I have an 03 AT sedan and just started to notice it. A man came up to me and told me my exhaust is lose and I thought he was crazy. I started to pay attention and noticed its a hard grind on a cold start up near the rear of the car. I have a full Stillen exhaust & filter on it, could it be that? I've had it for over a year now & the noise just started.

 

I have had this on both my sedans. Personally i dont think is anything could be just cold on start up.

 

I think I have this problem too. I have an 06 5AT sedan and it seems more pronounced when the car has sat overnight or during the cold season. When I turn the key, as soon as it starts, I hear a thunk or knock. It's really quick. It sounds almost like its in the lower steering column almost or behind the lower part of the engine. I have taken it to infiniti and they "cannot reproduce the problem"

 

This is my problem as well!! I have had my 04 at the dealer 5-6 times for this. The tech can hear it, but cant find the issue..... They gave me there 04 loaner the last time and it was doing the same dam thing, that was when I gave up the hunt. Having a mechanical back ground as it was my profession for a while, I have chalked this up to play in the motor mount/s. I have heard that they have fluid in them (could be wrong about this part), so when the car is cold, the extra torque from starting a cold engine jolts the resting mount and you get a clunk. The tech's at this particular dealer agree 100%. I have never been concerned about the sound, just originally thought I had a bad mount.....

 

i get it also normaly when the car has sat over night or for a few hours lol idk wat it is???

 

My 03 has done this since the day I bought it used over 5 years ago. It happens randomly. I'm not worried about it because it's never gotten worse and the mounts are still very solid.

 

03.5 5at sedan here, i have the same Knock on cold start only. im thinking its a common G issue and should not be worried about.

 

06 6mt here and i don't think i ever noticed it on my car but i guess in the morning ill have to listen for it ...

 

Old Thread but, has anyone found any new info on this?
I felt it today for the first time. Felt like something clunk'd against the brake pedal area. I also hear sometimes a clunk but only right after starting the car and moving maybe 100 feet. If I just sit and idle it doesnt happen. When you say WTF was that to your car, it makes you worry.