Need Help - Rattle during acceleration
 

Hey guys,

I have a G37 sedan that started experiencing a rattling noise while accelerating from a stop. It doesn't always happen, but when it does, it's always while in 1st gear and stops as soon as it shifts into 2nd. It's been to the dealer twice to investigate. The first time, they couldn't reproduce the problem. The second time, they said it was engine knock and retarded the timing by 2 degrees. Unfortunately, it's still happening. Has anyone had any issues like this? The clip below was recorded from inside the car with the driver's window down. The rattle happens around the 8 second mark.

never had that in the G, but sounds like knocking, so maybe the timing needs to go another 2..? what grade fuel are you using? honestly, it sounded like some of the older cars i had and the lifters needed adjustment, but i am not aware of the G, sure some pro on hear will give better advice- are you still under warranty by chance?

Is the car pictured in the video supposed to be the one that is making the rattle, because it's not moving at all. :confused2:

If the noise is present while revving the engine in park, then it should be very easy to determine the source. :dunno:

I have always used premium fuel, and yes, the car pictured is the one making the noise. What you're watching isn't really a video per se. It's an audio recording converted to video format so I could upload it to youtube. I just attached a still photo for something to look at :coolio:. It was recorded during a normal acceleration from a dead stop.

To your point, I have tried revving the engine in park to make the noise, but it never happens.

Sure sounds like knocking to me. Retarding the timing 2 degrees is a bubba band aid fix as they did not figure out WHY it is happening.

Knock or pinging can occur for many reasons and it is unlikely you will hear it with no load on the engine. The engine's computer adjusts timing and Air Fuel mixture for optimum performance and fuel economy based on a bunch of inputs. If any of these inputs are not right, the computer can screw up the timing leading to spark knock.

A failed knock sensor should cause a code but I would start there. You have no codes being displayed, right??

Here's a good article for you to read
http://www.wellsve.com/sft503/counterp_v4_i4_2000.pdf


WHat's interesting is that it only does it in first gear. That's something to think about. Modern engines knock here and there but yours is pretty pronounced.

Brian

One more note on knock sensor. THe engineers creating timing algorithms based on all of the inputs but they know it will be imperfect so one or two knock sensors exist on the engine. It's there to account for the imperfections in the timing maps. If it senses a knock it retards the timing. With the CONSULT tool, they should be able to see the timing be knocked down (probably to 0 degrees) when the knocking is happening. If the computer retards the spark during knock and it's still there then it's going to be a lot harder to diagnose..... if you have no codes.

It seems to me that if it truly is just knock, then the OP should readily be able to reproduce it in in a higher gear by lugging the motor. Attemptng hard acceleration or climbing a steep grade while in a manually selected gear that is too high (initially) for the current RPMs should be more than able to do it. First gear has enormous mechanical advantage given the torque of these motors, so if it is truly knocking in first, then most any gear, and especially the higher gears should incur far greater engine loads.

Besides ignition timing, I'm wondering if there is possibly a problem with the cam/variable-valve timing control.

.02

It sounds like metal rattling which right away I'm thinking the heat shield. But then not sure why only happen from 1-2 and not the rest. I guess just make sure nothing is loose in your undercarriage.

My 2011 X is doing the same thing at 1500 RPMs. Always at 1500 RPMs and I can duplicate this noise in both park and drive. However it is not as loud if revving in park.

I have an oil change coming up soon and will let the dealer take a look at it.

Hope it's something easy to fix.

Thanks for making this thread. I have this noise on my '11 X as well. My car runs fine and I do not hear this noise all the time, but I'd still like to know what it is. I have not been able to produce this sound in park, only in 1st at around 1,500 while pulling off from a stop. Was getting worried because we had a Sentra that was doing this and it ended up having low compression in once cylinder. The sentra would vibrate and run very rough, though, and the noise could be easily reproduced. The sentra eventually went to the boneyard.:icon09:

The first time I heard the noise I thought it wasn't my car. I heard it yesterday in a parking lot and there were no other cars, so I have accepted that it is coming from my car :(

I would take it in to the dealership since I have the extended warranty, but it happens so rarely that I feel they won't be able to reproduce it and will send me on my way.

I recall reading about a tsb for failed cats. Something inside gets loose and rattles.

I thought it might have been my cats as well. I replaced them with HFC's, and I still hear the rattle every once in a while. On a side note, the gains from the HFCs are great :eek3:

The dealer said it was coming from the drivers side catalytic converter. So they replaced it under the warranty.

I haven't heard the noise since but now I'm wondering if the passenger side cat will eventually make this noise?

Thanks for following up, and I'm glad you got it fixed. If you hear it again I suppose you can have the other one replaced. I'm not sure what my noise could be since I have already replaced the cats. Hopefully it's just some kind of shield. I wish I could easily reproduce it to troubleshoot it some more. If it gets more persistent I will report back.

Give it some time as it may begin to rattle while in park as well. Mind didn't at first - it took a few months. It just won't be near as loud as the audio clip above.

When I initially dropped it off, they revved it a few times and it finally made the noise which at that time they did mention the heat shield.