About 4 weeks ago I started to hear a rapid rattling noise when accelerating(between slow to moderate acceleration). This would happen between 1500-2000 RPM's and in 3rd or 4th gear where I could hear it the worst.
For the past 4 months I have been driving on 87 octane fuel with no ethanol.
I took it to my family mechanic and after driving with me for a while he said that it's most likely pinging. He told me that VVT-I engines coupled with low octane fuel and really hot temperatures(which started about 4 weeks ago in the 100F range) could cause that to happen. He suggested to fill up on premium and that the noise would go away.
Well, I ran the tank dry and filled up on 91. Within 3-5 miles of driving I could no longer hear the noise. And no matter what I did I could not get it to repeat whereas before it was very easy to get it to happen.
The problem appears to be solved. I just find it hard to believe that that is the case. Has anyone ever had this problem and found that premium fuel to be the fix? I took it to the Toyota dealer and they couldn't find anything(this was when already running on premium). They said it's normal.
I bought this truck in the end of September of 2010 so I didn't have a chance to drive it in hot temperatures so I don't know if the problem existed back then or not.
A little info on my truck. I have a K&N air filter installed and Pulstar Pulse plugs. Everything else is stock. After reading about the CAI intake causing the truck to run lean I thought that maybe the K&N filter might be doing something similar but I don't know. Haven't tested yet.
I have read all over the internet about Tacoma engine noise and can't find anything that describes my problem. I know about the injector noise and this is not it.
If anyone can help me out with some information I would appreciate it. Thank you.