Since I've never really heard it, I'm not sure what detonation in a VQ sounds like, but yesterday I heard a strange noise that if I had to guess I would think that's what it was.

I happen to be stopped at a red light and didn't have the CD playing so it was quite for a change. I heard a strange clunk then a few seconds later I heard it again. After listening carefully, I realized it was coming from the engine. It sounded like a misfire combined with a metallic clunk sound.

I pulled into the parking lot and listened for a minute and heard it a few more times. I let it sit for about 30 minutes while I ran into the store. When I came back and started up, it would still make the noise about every 10 to 15 seconds. I noticed that the idle speed was a little lower than normal so I held the pedal down to bump the idle to 800 then 1000 rpms and never heard the sound.

I drove it home over the next 1/2 hour or so, every time I stopped for a light, I would listen to the idling engine to see if the sound returned but it never did.

I'm sure I'll be paranoid this whole week and be listening to see if it returns.

Can detonation occur at idle? If so, what would cause it?

 

not sure why it would detonate intermitently at idle like that, that seems odd.

 

i know the noise ur talking about.. it sounds like a bubble popping out of water w/ some clunking right? It happens only at idle, and the car kinda budges when it happens. I've been told its normal, and im almost stock.

 

I have always noticed the normal pop from misfire at the exhausts and that sounds kinda' like a bubble. But this was a lot louder and had a definite metal cluck associated with it. I can't imagine that it's normal, especially since it only just started happening (the cars almost 2 years old).

I checked the plenum bolts and they all seemed tight. I'll check the vacuum hoses, etc. to make sure they're tight and no air leaks.

 

I had the same problem with my 03. Dealership acted like they couldn't hear it. I've got an 05 now and I have'nt had that problem (yet).

 

I have the same noise. I thought it was part of the "rough" idle the Z had but I guess not. Definitely sounds like a little backfire but I feel a clunk coming from the front. I bought it used and its always made this noise. It runs strong, just does this at idle. I'll be bringing my car to Nissan for the rear axles the week after next and wonder if I should mention it. My guess is that they'd blame the Pop Charger hehe.

 

Greg,

I'll have to listen to yours and see if it's the same sound.

 

I highly doubt its detonation, your not pushing alot of heat through the motor at idle or at startup and all the things u stated, so i dont think there is any reason why it would detonate. And this may be a long shot, but perhaps something with Timing? that seems to be more of a possibility then detonation.

 

I heard this yesteday myself...checked oil little dirty, had iol changed this morning didnt hear again today and I listened hard but my rear view mirror fell off...still not a good day.Check your oil maybe low or needs to be changed maybe??!! It solved my problem (knock on wood).

 

yea what about valve tap? possibility?

 

I had my oil changed last week - maybe I'll check it tomorrow to see if it's low.

 

Valve tap is usually just a ticking sound. This was a lot louder and more metallic than anything else I've ever heard in a car.

The good news is that it hasn't done it again since last Friday so maybe it was just a freak occurance.

 

I highly doubt that it's detonation. Only because it's very odd for any motor to detonate under idle. I wouldn't worry about it being detonation at all, the sound you are talking about is fairly common on Zs that I've been around.

Detonation can sound like popping popcorn or small explosions coming from your motor while driving.

 

detonation sounds the same as your brake discs sound while cooling.

btw it is called afterfire that yoou hear from your exhaust.

press clutch and check if you can still hear that noise from your car.

 

Same noise with both clutch in and out.

 

I agree, that is definately not detonation. Sometimes, if you get a low idle stumble, you will get a little bit of piston slap/rod knock, coupled with the associated vibration...can make it sounds a little clunky and metalic. I wouldnt worry about it...I heard similar noises from my 04 prior to going FI. With a 1000rpm idle now, I never hear any noises.

Detonation occurs under heavy engine load, and sounds like a rattle coming from the engine. Some people describe it as bb's in a coffee can. At WOT, you should hear nothing but the sweet sound of your exhuast, and a roaring strong engine.

 

Sharif.... you should write childrens bed time stories. Your post are soothing and make everything seem ok, and dandy.

Can you write one for me where my car doesn;t overboost and shred $1600 carbon clutches?

Of course at the end of the story I will get in my car and drive hard and boosting all the time to 20 pis and 600 rwhp, and live happily ever after (without anything breaking).

Respect
JET

 

LOL...thanks Larry.

 

I did notice that the idle seemed lower than normal that afternoon. Not sure why but so far, the problem hasn't returned. Just trying to be careful
Thanks for the feedback everybody.

 

i have the same problem..have had it for months...i figured it just part of the car...