I am having a weird noise come from under the hood. It sounds like pinging, but I don't think it is. almost a rattle.

I upgraded my stock 99 pcm for a nelson 02 with e-fans turned on. I also have catback and cai, but that is all for now.
A few hundred miles into the new pcm I threw a code. I forgot the number but it translated to thet truck running lean. After a search on this site, I found everyone who threw the code replaced their 02s and everything worked fine.
I replaced the 02s and spark plugs, but this problem is still here. The pinging starts around 4k and stops after 5500 rpm.

What do you think this is?

I normally run 87 octane and the highest I can get is 90. I will be filling my tank with 90 tomorrow when i am out of fuel.

 

not enough octane, not enough injector

most tunes are for 93!!!! you cant run 87 on high timing

keep it up and youll have headgaskets blown soon

 

It is a stock 02 tune.

 

02 is tuned differently then 99. a few things are different and i think injectors might be one also

run 93 and youll be fine

 

I cannot get 93 anywhere in alaska. I can get 90 only.
I can also get 110, but it is like $11 a gallon. What would be the mixture ratio to achieve 93?

 

What altitude are you at up there?

 

Sea level. I live right next to the ocean.

 

run 90 and use a bunch of octane boost!

 

If you're running an 02 PCM with 99 injectors it will run lean. The 99 injectors flow less than the 00 and up injectors, therefore the 00 and up PCM's are tuned from the factory to duty cycle less. (I believe the 99 injectors flow 21 lb/hr and 00 and up flow 24 lb/hr). First thing I'd do is upgrade the injectors if you haven't already done so, and maybe contact Nelson and get his take on that. Another thing I'd check for a lean code is the MAF...make sure it isn't covered with junk or air filter oil (if you have an aftermarket oiled air filter)

 

I threw a code, p101 which had something to do with the MAF, so I cleaned it. I also replaced the fuel filter which was a pain in the ***, and cleaned the throttle body. Then I put some 90 octane in the tank. (90 is the highest I can get from the pump) The pinging is almost gone. It only rattles near 6k, so i think I will mix 5 gallons of 114 with 18gallons of 90. The only problem is that a tank of fuel is now over $100.