engine predetonation?

My 2011 Taco 4.0L V6 started making a engine "rattling sound", like pinging, but not as "tenny" sounding. Its hard to describe, it happens at low speed, 35mph or below, under very light acceleration(enough to maintain speed). It sounds like it is going to ping and just "rattles" instead. I took it to dealer and they said its normal They called tech services and the guy told them he has a 2012 Taco that makes the same noise, said it is the VVTI. I tried a tank of premium and the noise stopped which kinda doesn't support the VVTI theory. Anyone else experience this "rattling noise"?

 

The solution is to hook up one of the Toyota diagnostic computers and look for knock events in the ecu. If its out of specification it will throw a check engine light but they should be able to see the knock count in the ecu anyway. Bad gas will cause pinging, even crappy gas (in this area that would be wawa and royal farms). Try filling up at a shell station with regular and see if it knocks.

 

Mine will ping like that on regular gas every time. I just run premium instead, although most of it is gone on midgrade.

If you get a lot of pinging even in those sporadic situations, the ECU starts to pull timing everywhere (I've seen it happen real-time on the ultragauge) and cruising mileage will take a dump until it tries to bring it back up again.

 

My 2012 does the same and it really pisses me off. Dealer swears up and down that its not an issue. I run premium too.