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I have noticed a possible problem on my car. It also happened on my old car, a Mazda Protege5. On both cars, it didn't seem to happen when it was very new, but now that it's got some mileage on it (I'm at 33000 KM or so), I am noticed a bit of detonation or pinging at first mainly during some shifts. I am lately starting to notice it occuring not only on shifts but also when I start to accelerate for a second, and then I guess the knock sensor adjusts the ignition timing and it goes away. Anyone know what could be causing this? On my Protege5 I figured maybe the injectors were getting dirty so I had the dealership do the recommended injector flush on in, but that didn't fix it. I also put in new plugs and that didn't change it either, neither did a K&N air filter. It is only for a split second, not persistant or anything but more and more frequent.
Why is this happening, is it normal, will it cause damage, and is there anything I can do about it?


Two things.  1.  It's time for a tune-up 2. only burn premium gas

I have been following all normal maintenance so what kind of tune-up? The car is rated for 87 octane and has been fine on that since it was new so why would that change?

If it is a 2007 GT 4.6 liter 3 valve engine rated at 9.7 compression ratio.   You might get away with burning 87 if your engine is tuned to perfection.  But when you stomp it and it sounds like marbles in the engine, then you could try a higher octane gas.   As far as a tune-up, about all you can do is to change the spark plugs, so you may as well take it to a Ford shop and have them hook up their expensive and fancy computer to see what needs tweaking. 

You're right about the octane. I was always under the impression that it was best to use the octane that the owners manual calls for, which in this case is 87. I tried 91 octane fuel and she runs much nicer. I was a bit skeptical because I also tried this when I had my Protege5 and it didn't make much difference. Thank you.


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