New noise tonight - realize difficult to diagnose through forum. Was running errands for about 2 hours without issues (multiple stops) and last stop was for fuel. When I started to leave heard the sound below. Killed engine, started again and same noise. Drove home without issues, plenty of power, no CEL. Video below is once I got home and I started twice.

Sound occurs just as engine fires. Initially thought it might be the starter but I'm not sure as it almost sounds like a diesel for a moment. I can't imagine it's the fuel as the rails wouldn't have had the new gas on first restart. I run BP and have always used 87.

Thoughts?
Eric

 

Try 91 on your next tank. That sounds like classic detonation from insufficient octane.

 

87? Wow not good.

 

Thank you for your input!

I'm heading out this morning to get some octane boost as it's a full tank and will take a week or more before I need to refuel.

-Eric

 

I know.

Threads on here talk about whether premium fuel is needed and the opinions go back and forth. My wife has a MINI Countryman S All4 that calls for premium only (91) but she received a letter from MINI stating by law she didn't need to. However, while researching this last night I found an article on fueleconomy.gov indicating the manufacturer's recommendation should be followed.

-Eric

 

Picked up a 15 oz. bottle of Lucas Oil octane booster then drove 15 miles highway and city. No change yet as it did it when I got back home. It's cold here (8 deg) and when I did a cold start this morning it sounded normal.

Assuming it may take some time? Would an ECU reset help as I've been running 87 since August and about 6k miles?

-Eric

 

Curious why 87? Did you just not know. First premium car?

 

Been running 87 octane since the purchase of my 06 G35 on 12/31/2005 and put on 171796 miles before trading it in for my present 2012 G37S purchased on 8/31/2012 that now has 94k miles

Never had a problem using 87 octane!

We had two below zero here a few weeks ago and had no problems and I never use any additives.
You've got something else wrong and it is not the gas.

Telcoman

 

but you wouldn't notice. You dont rev past 3k LOL.

 

Not at all.

However, there doesn't seem to be a "black and white" answer to using lower octane fuel and other than this issue I've never had ping or detonation.

-Eric

 

Hmm...my concern as well.

Have any thoughts or ideas as to why it sounds like this? I could get a high quality recording but as I listen it sounds like its in the ignition sequence. Fine when cold however when warm it's like the automated start is releasing a touch too soon and while the engine does fire it sounds like it could use another 3 - 5 seconds of crank (if this makes sense). Almost like releasing from crank early with a traditional key start.

-Eric

 

My guess is something starter related. I can't see how fuel octane would play any role when starting the car (unless its like 50 octane which would not be suitable for a gasoline engine anyway). Sounds like the starter gear is not releasing early enough or something.

Detonation will typically happen at higher rpm/engine load.

 

Last oil change was when?

 

11/20/2017 @ 69,852 - Mobile 1 Synthetic w/OEM Nissan filter.

Currently just over 72,000 (+/- 72,050).

-Eric

 

Here's an update:

As I mentioned earlier, I added the Lucas Oil octane booster and drove for around 20 miles with no change as the car still made the noise with immediate re-start.

Car sat for 2.5 hours (it is cold here @ 10) and didn't make the noise when re-starting. Drove to an appointment and shut off for 50 minutes - no noise when restarting. Picked kids up (early out for snow) and went to a restaurant (Chinese buffet so quick) and the car sat +/- 30 minutes - no noise when re-starting. Drove to a pet store - sat for 15 minutes - no noise. Came home and parked in garage and re-started twice (similar to video) with no noise.

@slartibartfast might be on to something and I'll admit I'll be shocked (but pleasantly surprised) if its the octane (I use BP only). I'll keep an eye on it through this tank of gas as it's too early to tell.

-Eric