Pinking?

[ErrErrminator]

I've read a couple of posts on this from a quick search and opinions seem to vary from 'they all do that to some extent' to 'oh heck, better get that looked at'.

Driving my car last week and on Tuesday this week (both days around 25 degrees) I noticed that the engine made a noise resembling one I remember from my earlier motoring days. When pressing the throttle from relatively low revs with a bit of load (ie going up hill) there is a very brief, but quite distinctive pinging, or pinking sound. It also happens if I blip on downshifts. Now I would have thought that a modern car with knock sensors would not suffer with sub-optimum combustion. So is this a problem with the car, or effects of the warm ambient temperature, or the fuel?

I will monitor it over my next few drives, but as I am currently half way through a tank full of Esso 'super' I was somewhat surprised to hear this noise. I did hear it a little on the previous tank of 95 octane, but figured, as it may be fuel related, the super would see it diminish. It hasn't, or not yet at least.

Any comments, thoughts, similar experiences? Car is a pre-facelift 2.5i, so M54.

 

[ph001]

I would bet it's fuel. My previous Z3M (S54) used to pink badly under load at <1,500rpm if run on 95RON. It was much better on 97RON, so maybe you just got a bad batch. I think very slight pinking is normal though but it's not recommend to labour then engine at very low revs anyway.

I did ultimately find out that the Z3M had low compression on cyl6 so the 'pinking' noise I thought I was hearing was probably blowby or something similar. Quick compression check on each cyl should confirm if you find that fresh 97RON doesn't help.

 

[Rich8]

Id say probably fuel, but would have thought knock sensor would stop that.
Even 95 ron shouldnt result in pinking as still pretty high octane rating relatively speaking (they sell some really crappy low octane fuel in the States and some places on the continent - so if they are made to deal with that you shouldnt get problens with UK fuel - unless you stumbled on a cruddy batch).

I havr read that it can sometimes take over a tank before the management system adapts to the different octane rating. Maybe run another tank of decent 97 Ron through it and see if it goes away before getting the spanners out.

 

[mr nurburgring]

My 2.5 had done this for 8 years, only when I use 95 Ron and when it’s hot.
If I use 99 Ron momentum it doesn’t happen.
I wouldn’t worry too much.

 

[Smartbear]

I’ve heard worn vanos seals can cause a light rattle at low rpm not unlike pinking :?
Rob

 

[john-e89]

Also if the Disa valve ‘O’ ring is on its way out it’ll let air in, causing pinking, well worth checking, very easy job.

 

[ErrErrminator]

My car has had both Disa valve and VANOS dealt with within the last year or 18 months, so both should be good.

 

[ErrErrminator]

Nearly through that tank of super now and a good few miles in 27 degree heat on Monday I noticed the pinking noise was reduced, but not completely absent. Going to top up with the good stuff again and see if the improvement continues.