Pinging in my 4.8is

[Scott in Cincy]

Originally Posted by BIMMER DUDEE

Knocking or Pining? How many miles are on the car? I had the same problem. Let me know, I think I can help, through my experience...

Definitely pinging, not knocking. To me, knocking is a crankshaft issue and is due to oiling problems. This is a gas/ignition problem.

Any ideas? The car has about 20k miles on it now...

Thanks!

[LVR]

It's detonation.... cause unknown as yet. It is NOT normal, and is a prelude to pre-ignition which means $$$$$$$$$$$$$$$$$$$$$ It can occur for a very long time before you get to that and in some cars can never get any worse. My 4.8 goes in to have the engine opened up in 2 weeks time.

Generally it occurs when the engine is warm from having been driven around town. It can be replicated by light throttle on an uphill incline which puts the engine under load but not enough to cause the trans to kick down.

That means when you are driving any road with a slight incline you have to force it to kick down to avoid the detonation. Not good.

I have had 4 software attempts at fixing it, have driven for 10 months with nothing but BP Premium 98 (as it has a detergent) and been told that this engine cannot have carbon build up.

The inlet manifold is coming off and an internal examination of valves, combustion chamber and cylinder walls together with a compression test is next.

Will let you know what happens........

Cheers Vin

[Thunder22]

put a tank of chevron in it, and if you don't have chevron in your area, but a bottle of this in your tank on your next fill up:

http://www.autobarn.net/ch67740t.html


trust me.... it works.

[bsprtsgrp]

I think that Redline S1 Cleaner is an approved BMW additive, ask first before you use it

[zero]

What exactly is pinging?

[fln8tive]

Has to be timing advance IMO. Check the oil level, the VANOS timing goes awry with low oil.

[jpm4.8is]

Originally Posted by zero

What exactly is pinging?

Could someone describe pinging for us?

[LVR]

The combustion process of igniting the fuel air charge is designed to expand in a certain way so that the whole charge is spent. It creates a 'wave' of flame as it expands. Engineers and fluid computational dynamics are used to design a more efficient shaped chamber, allowing ever higher efficiency of power vs consumption. Sometimes you get less efficient consumption of the charge. If some of the charge is unspent it explodes out of sequence and creates a shock wave that is so powerful that you can 'hear' it ringing in the engine structure. That is why a 'knock' sensor is really just a glorified microphone.
It is a precurser to pre-ignition, (which is different).

[JCL]

Pretty good, but here is an explanation in plainer english.

Fuel and air is mixed in the combustion chamber. Piston approaches TDC (top dead centre), compressing the mixture. Spark plug ignites mixture, just before TDC (to give it time to light up the charge). The mixture burns, it doesn't explode. As it burns, the flame front moves from the spark plug out to the cylinder walls. The mixture expands, thus driving down the piston on the power stroke. All this is in an ideal situation.

Two different problems can occur (well, actually, lots of problems, but here are two):

As the flame front moves out, heating the remaining mixture, the mixture can explode instead of burning (due to the heat, and in advance of the flame front). That is pinging. It creates a metallic, hollow sound, a little like rocks being shaken in a steel can. It can be reduced (prevented) with higher octane fuel (more resistant to ignition), lower temperatures, better combustion chamber design, etc. Very heavy pinging can produce a knocking sound.

Pre-ignition occurs when a hot spot ignites the mixture before the spark plug does. It can occur from pieces of carbon in the combustion chamber that glow very hot, and act as an ignition source. Pre-ignition is any condition whereby the mixture ignites before it is supposed to. Pre-ignition can lead to pinging, and pinging can indicate pre-ignition, they are related, but different.

Hope this helps.

[Scott in Cincy]

Originally Posted by gresch

put a tank of chevron in it, and if you don't have chevron in your area, but a bottle of this in your tank on your next fill up:

http://www.autobarn.net/ch67740t.html


trust me.... it works.

I just did that, with no avail.