I'm not even sure if that's how it's spelled:o Anyways, I was cruising home with my wife and decided to punch it going up this big grade that stretches about 1.5 miles. At WOT I hear this funny rattling sound from under the hood! I'm like, "Did you hear that?" My wife says,"Yah, it sounds like a can of marbles." I let off throttle immediately and just cruise home at grandpa's pace.

My first thought are...detanation. Now, I'm wondering what's causing this that wasn't for the last two weeks? Could it be the crappy gas here in California (91 oct.) or the hot temp's? It was 97 degrees out at the time of this occurance. I just got this 4-way chip back from Sal, with upgraded programs. So, maybe they weren't programmed for 91 oct? All I can say is that I have NEVER had this happen before in my L with old programs(4-way) and same pump gas (91 oct). I'm concerned about the possible damage to engine. Anyone have some answers? I would appreciate it very much!

What's amazing is that we could hear the rattle over the Bassani exhaust and full boost whining at WOT.

 

Yep, sounds like detonation. Do you have a stock program on your 4-way chip. If you do run it until you get rid of the fuel in the tank. Heavy load (long up hill) on top of high heat with bad gas is going to be a problem. May want to try another brand of fuel. I have good luck with Texaco & UniCal76. Had problems with Chevron. We have the same crappy 91 oct here.

 

Yep, that's exactly what I did. I do buy my gas at Texaco, however. Maybe it was the high temp's. I saw 101 degrees a few times today! I figured since the stock program is rich, I'd be safe for awhile. At least until the temp's come down or this tank is gone. Thanks for the advice, Silver-Bolt.

 

It's the high temps and low humidity. If you run a water/alcohol water/vapor injector the problem will disappear, otherwise, when the temps get above 90, just watch it a little.

 

Defintely with the long grade and weather you in essence simulated towing with the extra work put on the engine. Towing is frowned upon with a chip.

 

You're probably a victim of the new gas formulation in CA. We used to have 92 until very recently, when everyone went to 91 in anticipation of getting rid of the MTBE additive, which is being phased out in CA in favor of ethanol for 'environmental' reasons (MTBE was cheaper to get the octane rating to 92 than ethanol, hence the drop in the octane point to keep similar prices - mid grade will be down to 88.5 shortly).

My chip ran great for over a year before this happened, and then the first tank with 91 and the pinging started. You should be able to get it reprogrammed with no problems, although you'll lose a few HP in the process