Detonation/Pre-ignition?

[Hon2bmw]

Does this sound like Detonation or pre ignition? I ran a tank of 91 over the last week and it did not make a difference. In the video I am holding the brake and giving it throttle while the shifter is in D. It only happens under load after the car is fully warm, and get louder/more prevalent the hotter the car gets, this was just after driving in rush hour stop and go on the 101. I pulled the spark plugs and they look fine, not sure if there would be any indication on them.


http://youtu.be/sgQ5denSIhI

 

[lostmybook]

Definitely sounds like pinging to me. I would give you suggestions, but my pinging is probably related to my higher compression. Is this a stock motor? The occurrence of the pining (under load after warm) is the same for me. This is what I did to really confirm that it was pining:

Drive the car to low fuel levels and find a 76 Station that sells 100 octane. Get 2 gallons or so of that and drive it under load. If it goes away, then you know. I still ping with 91 octane but definitely not that much.

 

[Hon2bmw]

From passenger side (plug # 1) to Driver's side (plug#4)

Plug #1


Plug #2


Plug #3


Plug #4

 

[Hon2bmw]

Definitely sounds like pinging to me. I would give you suggestions, but my pinging is probably related to my higher compression. Is this a stock motor? The occurrence of the pining (under load after warm) is the same for me. This is what I did to really confirm that it was pining:

Drive the car to low fuel levels and find a 76 Station that sells 100 octane. Get 2 gallons or so of that and drive it under load. If it goes away, then you know. I still ping with 91 octane but definitely not that much.

Yes, stock motor.

 

[hornsfan10609]

A coilpack may be failing

 

[thuzil]

Check your knock sensor?

 

[Hon2bmw]

Replaced coils, wires, and plugs this evening, no change, will check the knock sensor tomorrow. Its on the back of the block above the oil filter on the FS motor right?

 

[lostmybook]

Replaced coils, wires, and plugs this evening, no change, will check the knock sensor tomorrow. Its on the back of the block above the oil filter on the FS motor right?

Yes. It looks like this (this one's polymeric material has melted away though).



How long have you had this problem? How many miles on the car? Have you checked for vacuum leaks or fuel pressure (you might be running lean)? Do you have an OBD II scanner to check your coolant temperatures? Is there air in your coolant system? Is your thermostat malfunctioning? Is your compression ratio artificially high (carbon on pistons)?

Also, off topic but are you running iridium spark plugs?

 

[Hon2bmw]

Installed NGK BKRE5-11 plugs last night.

Its been happening ever since I got the car, so for about two months.

Would I not see some indication of it on the spark plugs?

Dealer did the waterpump/timing belt last month and drained/refilled the coolant system, I know the idiot gauge on the dash is buffered, but it has not overheated, the level in the overflow bottle is consistant.

Although I'm having a hard time capturing the noise in the video, it is VERY loud from outside the car, would this be normal with detonation/pre-ignition? The fact that it is so loud makes me think that maybe its a damaged Catalytic converter rattling or my exhaust?

It happens under partial throttle, and oddly while accelerating it starts off happening only when the transmission shifts, basically during the time period before the clutch packs engage while there is little to no load on the motor. Generally if I floor it or get past a certain throttle postition it goes away. While cruising, I can gently push the throttle and get it to start rattling without effecting the speed of the vehicle.

Would I not be getting a CEL if the knock sensor was malfunctioning?

 

[thuzil]

Hard to really tell. It sounds like heat shields rattling to me.

It seems to be too irregular to be associated with the engine.