Yesterday I started up my 02 Q45 w/58k and the engine sounded like a 100 year old diesel that was about to explode. For a moment, I thought something was hanging loose near a belt and was knocking it like a playing card in a bicycle wheel. The racket changes with RPM so its not the radiator fan. Its a clicking that sounds like the valves. Oil is full with less than 2K on the last change. I took it to a mechanic who confirmed the loud clatter sounded like the valves but was unable to diagnose it, asked me if I knew of any TSB or other info, and suggested I take it to the dealer, which is the LAST thing I want to do. The only even remote possibility that comes to mind is that the day before I pulled the air filter housing and MAF to get to the headlights. I did nothing to the MAF sensor and I did hook the harness back up to it. Could this be an issue related to the MAF? But it so. I would have thought the issue would have started as soon as I put everything back together - but it ran fine afterwards. Oh - no warning lights are illuminated on the dash.

Anything that will help me avoid the dealership is much appreciated. Thank you.

Interesting.. I wouldn't suspect any valve noise like that.. Does it sound the same if it's warmed up or cold? Sometimes exhaust leaks can sound like really bad news when obviously an exhaust leak isn't as big of a deal as valve..

Here is a strange tale...

My mechanic confirmed that it was internal mechanical engine noise - not computer induced or a worn serpentine belt. No warning lights, so nothing to pull a code about. I called the dealership who said.. well, you know how that sentence ends. I spent time searching the web for news or insights and found a couple comments where owners had similar things happen and the dealer said it was normal. One post said the dealer told him that the engine tolerances are so tight on this model that a very small amount of excess carbon build up on the top of the piston can create noise like this. His suggestion was to floor it and blow out the carbon. I said to myself, Really? I thought we were past that point in engine technology. But I gave it a try. The noise quickly built up to be really ugly for a couple seconds at the most, then all was silent. I mean in a good way - not that the engine died. So this morning everything is fine. Hmm

Strange tale indeed... I'm glad it worked out though!

Sadly your Q's engine is intentionally built a little looser than most Nissan/Infiniti engines... this was part of how they milked more HP out of it. Also why they had so many engines with oil consumption issues.

I would consider an oil change, even if it's not due... it's possible you have some sort of filter issue.

Heath

lmheim wrote:One post said the dealer told him that the engine tolerances are so tight on this model that a very small amount of excess carbon build up on the top of the piston can create noise like this. His suggestion was to floor it and blow out the carbon. I said to myself, Really? I thought we were past that point in engine technology. But I gave it a try. The noise quickly built up to be really ugly for a couple seconds at the most, then all was silent. I mean in a good way - not that the engine died. So this morning everything is fine. Hmm

It sounds kind of wonky, but it's a valid explanation.

I experienced the same thing with my Civic - Only took a couple minutes of engine operation to pulverize or blow out the carbon chunk.

That's an advantage of occasionally doing an "Italian Tune-Up" - It helps remove small deposits before they become big ones.

Glad everything went well. WOT is my fix for everything at this point. Still cant blow it up. 58k miles on your 02 ooooooh I would baby it all the way. Hope that is one of the few negative experiences you have

lmheim wrote: One post said the dealer told him that the engine tolerances are so tight on this model that a very small amount of excess carbon build up on the top of the piston can create noise like this.

doubtful.
As Heath said, the ring tolerances are loose on the VK45DE. But.....
Maybe it's all related: The carbon could create a local hot-spot, and oil getting past the rings will autoignite easier than the air/fuel mix (google LSPI).
As long as the bottom end is sound, at least 1 redline a week (fully warmed up engine of course) is considered good preventive maintenance.

That description sounds like the clatter you get with an oil change and not prefilling the filter. The oil is all in the pan and takes some seconds to be pumped up to the valves. I'd really take a look at that filter. If it's Puralator classic, I've heard of some QC issues where they fail internally. Could also be an oil pump issue?