engine pinging when cold

[Jules]

Good day
i have a 2005 LS Aveo , 215000 on the clock .
i experience a sharp pinging noise when accelerating when engine is cold, and have to lift off throttle to make it go away , but returns as soon as accelerating again,so have to creep forward gradually , a bother in traffic around Cape Town .
this lasts until engine reaches half way to operating temp .,, then the noise is gone . have had it at Thorp /GM workshop on and off for around 8 months, they done all kinds of computer resets ,
the longest the noise was away for was 2 weeks , then it comes back , slowly, until about a week before it is back with a vengence.
Have also replaced the concertina air flow pipe alreadyand done a cambelt change , recently the HT leads were also replaced .
anyone have any experience with this ?
regards

[2010AveoLT]

What type of fuel are you using? Usually pinging is caused by fuel with an octane (AKI or RON rating) rating that is too low to where the fuel charge is preigniting before the spark plug fires.


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[Jules]

good morning
thank you for your response
i am using the South African standard 95 octane unleaded as per the user manual .
the mechanics at the GM workshop confirmed that this is the correct type. they will attempt now to replace the "Loopback coil"(not sure if thats the correct term ) box where the HT leads run from ?
They will give me a shout when the part is sourced , i will feedback .
regards

[MetroMPG]

My first thought is the same as 2010AveoLT's:
detonation problem caused by low fuel grade. Possibly also timing is faulty (too much advance). I would try a higher grade of fuel just to see if it helps.

Considering timing is computer controlled, I'm not sure which sensor you would have to check. I'm not even sure if the Aveo has a knock sensor.

Keep us posted.