Last weekend was towing my trailer and started going up a grade then the engine started rattling, sound like it was coming from the top end. It then started loosing power so as I let off the gas to a certain point it went away but everytime I would give it gas it would start making noise again. At one point the "check engine" light started flashing it then went out after about 30 seconds. I had this happen once before while towing this trailer. I was running middle grade gas due to a modifiyed tune. Without the trailer I cannot get it to duplicate the noise and it seems to run fine. I used my programmer to check for codes the day after this happened but came up with nothing. Any clues on what is going on?

 

Sounds as if you are running very lean. If you have a programmer, back off on the timing a degree or 2 when towing. Otherwise, use a higher octane.

 

California gas is garbage. Use the highest octane gas you can get when you tow, and if you have a programmer, get an 87 octane towing tune.

How many miles on the sparkplugs?

 

About 5000 on the plugs, And I was running a 87 octane tune using 89 octane gas.

 

do not run a higher octane gas on a lower octane tune.

it is ok to use a lower octane gas on a higher octane tune as long as you dont get detonation or pinging. i have my truck tuned for 89 and use 87. i think i get a little more out of it.

think about it. octane pretty much means how easy it is for the gas to burn. a higher octane means the gas is harder to burn. so if you put a lower octane in (easier to burn) you, in theory, are getting a more complete burn.

 

Scuse me - he's getting spark knock - this means a HIGHER octane fuel is needed to prevent damage. I don't care what it's tuned for.