hello everyone - n00b here
just bought truck in sig....
previous owner has been runing 93 octane he says better gas and performance no chip
a mechanic friend says that if truck was run a long time on 93 octane and i revert back to 87 octane i could develop a ping
blkjak

 

You won't know unless you try it. I doubt it will ping.

 

<p>Me neither. I don't think the PCM &quot;learns&quot; to advance the spark by itself when using higher octane gas. I think you need a programmer for that. The truck was designed to burn 87 octane, so, it should be fine.</p><p>You could always introduce the lower octane grade gradually, by filling it with that when the tank is no more than 1/4 or less empty if you're concerned.</p><p>- Jack</p>

 

You can fix it real quick.
Remove the battery cable for 1 minute, then reconnect.
This will reboot the computer and clear all learned data.
It will rebuild the fuel and ignition tables within 2 or 3 drive cycles to your style of driving.
Good luck.

 

Put a bottle of Gumout for high mileage engines or Chevron Techron in the first tank of 87. That will help clean out deposits.

 

thanks everyone for reply's - blkjak

 

The PCM does indeed learn to adjust ignition for fuel quality vs load and air temperature.
As the table inputs are increased or decreased, the average table values change.
For a difference in fuel, the Ox content can change depending on what is in the fuel.
For example, extra alcohol generates extra oxygen in the exhaust and causes richer fuel additions.
The average rotation time due to the heat content of the fuel changes table values used.
The system has to have the ability to change for the different fuel sources that are put in the tank.
The TPS angle needed to attain the requested power is included in the overall fuel and ignition points developed at any given moment and affects the mass air measurement volumes vs throttle angle.
The system is much more dynamic that most ever believe.
When a programmer is used, changes to the table bases values are usually made.
The dynamic actions of running average changes remains the same.
The averages that result are moved the amount of the table base changes made.
Good luck.

 

thanks for the info .... blkjak