Ok I have a 2002 Nissan Maxima with almost 125,000, I use Shell 93 Vpower for gas. Ok well I recently have been having this engine rattling which sounds like its coming from the lower part of the engine. The noise at first was only when I turn the car off as the engine is turning off you hear a rattling noise. Now I am getting this rattling noise when I am just idling in park or neutral but goes away in drive. Also as I rev the engine to about 2000rpm when I let it go as its coming down you hear it some more. I take good care of my car Idk what could this noise be or what could have caused it anyone who has an idea or any help would be greatly appreciated thank you

 

Could be your exhaust, could be anything. Can you upload a video? It will make it a bit easier to diagnose.

Nevermind the exhaust part. Just saw it does it with the car off?

 

first thought, precat rattle

 

did you ever check the heat shield by the precats. That was the cause of my rattle...well one of my rattles.

 

um how do I upload a video for you guys to see....Video is already made

 

I usually put it on youtube and then put the link here

 

I 2nd this, and check ur oil

 

I 3rd this also....

 

I...4th this? O.o

 

HERES THE LINK TO A VIDEO OF THE NOISES

https://www.youtube.com/watch?v=9yzd...e_gdata_player

 

You made the video private...make it public

 

Try it now...it should be public now sorry about that

 

Best guess is also, based on the video, one of your heat shields. There are several, around your front and back pre-cats just after the exhaust manifolds, as well as around your main cat, and between your exhaust and floor(unlikely to be these). You mentioned it doesn't rattle when the car is cold? As the car heats up tolerances get larger between the heat shield and retaining bolts and allow play. If one is loose, most people, myself included, just pull off the shield. The shield area around the retaining bolts rusts over time-plan B is get 2 washers (one under, one over the shield)and see if you can reinstall the shield-but be careful removing the retaining bolts or you'll break them off as they are probably rusted.
End of thesis

 

oh no, that sounds bad. i dont think that an cat. hows your oil level? u might just want to take that by a shop or 2 and get some estimates, just to see what they come up with

 

But if it was one of the heat shields wouldnt it rattle while driving??

 

I know tell me about it its stressing me out because I hope its not something too bad but idk I gotta get this figured out....and oil level is fine, oil changes are done often

 

That does not sound good. I 2nd bringing it to a shop.

 

Sounds like a busted timing chain tensioner.

 

First guess from the 2,000 rpm rattle sound is a pre-cat with the catalyst material broken or loose inside. Remove and inspect, you'll need exhaust gaskets if you do remove the pre-cat(s).

From listening to the video it sounds pretty serious in that if it were me, the car would be on a flat bed into the shop next business day. You can pick up one of those stethoscope Poke it around the engine from the top and if you can from under the car, where you hear the noise getting louder thats the area you want to focus on.

 

Bumping this thread to see if OP found the cause for the sound.

I have the exact same sound, when I rev the engine in neutral as I release the gas and the rpms drop, or when I shut off the car. Doesn't rattle when I'm idling.

My oil level is good as I top it up frequently (burns about 1 quart in 3,000 miles) and I pump shell 91, sometimes Sunoco 94. Not throwing any codes either an car runs great and everything feels normal except for the rattling sound.

Question: would a loose precat make a rattling sound without throwing a code? Or does a precat failing always throw a code?

 

They do not have to throw any code. In fact, it can kill your engine and no code will ever show. Yet, (nearly) everyone thinks it's okay to leave those POS in there.

Sounds like the typical cat rattle.

 

Thanks.

I should've also mentioned it doesn't rattle when I'm driving around either. Seems like it's coming from the bottom of the car near the main cat; so I'm thinking its the rear pre-cat. Just ordered the O2 extenders, I'll get the pre-cats gutted as soon as they arrive.

 

thats rod knock, need a new motor

 

The reason I don't think it's rod knock is because I only hear it in the above scenarios and not while I'm driving around. Would the sound not be more consistent and frequent if it was a rod knock?

Also, it's been doing this since the summer around July/August and I've been driving it around with no problems. Even did a couple 600 mile trips.

 

You can tap the cat with a hammer and listen for the rattle sound. I had the rattle noise if the engine was revved and it was gone once I replaced bank 1 pre-cat.

Now my main cat is acting up.

 

You replaced your pre-cat instead of gutting it? Any particular reason for that? At this point, I'd like to go with the most cost effective way possible. Wondering if it's cheaper to replace the pre-cat than paying my mechanic to gut it for me.

 

Just keeping things factory/stock. For simplicity's sake.

To gut the pre-cat you've just got to remove it, then punch out the material. Drop on some new gaskets and you are set. Do some reading on the topic so no surprises pop up.

 

Were you able to fix your problem? I've been having the exact same issue. But I also have to Code P0420, Guess I'll have to go take care of the cat. Videos:

knocking/rattle noise:


And when turning off the car:

 

I just started having the same problem after an oil change. Havent figured it out yet damn its annoying.

 

After lifting the car, pinned the sound to the pre-cat (the bank 1 closest to the firewall). Taking pre-cat out, sure enough piece of the honeycomb mesh came out. Will be replacing the pre-cat

Got a Tread with more info: http://forums.maxima.org/5th-generat...ml#post8746565