2010 Mazda 5, 30000KM with auto tranny.
For the last 2 months, engine pings slightly when engine on 1500 - 2000rpm on 5th gear, or slow drive off from stop, engine pings, I always use regular unleaded, now switch to premium gas but no difference.
I took it back to dealer, but they said they cannot hear the noise, will have to wait until it is more noticeable, but the noise is always there, the only way for the noise to go away is to manually downshift or step on gas to get the transmission to shift to lower gear.

Wonder if changing the spark plugs help, or just timing issue.

But the dealer insist they cannot hear the noise, it is tought to get them do anything.

Any suggestion would be very much appreciated.

 

A couple of comments:

1. Light pinging is considered "good" by a huge number of automotive engineers. Why? Because that means that the ECU is keeping the engine right on the very edge of incipient detonation (which is the best place for both power and fuel economy).
2. Running Premium gasoline in an engine designed for Regular is never advisable as higher AKI fuels can lead to lower fuel economy and increased deposits within the combustion chamber.

 

Did you find a solution to the pinging?
I have a Mazda3 2011 automatic with 25,000 miles that if I step gently on the gas while going uphill will ping just before it downshifts, even a slight hill can cause pinging with just the right pressure on the gas pedal. I have tried all major brands of gas, no difference. the dealer does not hear the noise and says that because the check engine light is not on there is nothing for them to look at.

 

Using a higher grade fuel does absolutely nothing. I had suspected this for a long time, but generally it is a scam. Automotive experts seem to agree.

On an episode of Marketplace on CBC they did some interviews and dyno tests and saw NO difference in performance of mileage what so ever.

Premium gas in regular-fuel cars not cleaner, expert says - Canada - CBC News

Anyways, don't waste your money on higher grade fuel. Just throwing away your money!

 

On my 2007 Mazda 5 when this started to happen at around 60K miles, I replaced the spark plugs and used fuel injector cleaner and that stopped the pinging I experienced when accelerating up a hill. I am currently at 83K miles and haven't had the pinging return. Knock on wood.