93 Octane Leading To Rough Idle And Near Stalling?

[02 Sonic Blue]

I recently filled up my car with 93 octane gas to see how it would run. Previously I had ran it on 87. Now when I start the car it has a very rough idle and nearly stalls out. It does this for about 10 minutes untill the engine gets warm, then it idles fine. Should I be concerned? Is there an additive or something I can put in to neutralize the added octane? Only other option I can think of is just burn through this tank of gas quickly and re-fill with 87.

The engine is essentially stock with a b-cam and MSD wires, it has a full exhaust, headers, midpipe and catback.

 

[Rick 91GT]

The higher octane will burn a little colder but shouldnt have the effects you list. I would run some dry gas in the tank, sounds like the fuel you got may have some water in it

 

[jrichker]

See the "Surging Idle Checklist” for help with all your idle/stall problems. You can guess at the problem and throw parts at it, or you can use the checklist to help you find the problem quickly and inexpensively. The checklist is right here in the Stangnet 5.0 Tech forum and you don’t have navigate to some other unknown web site. It‘s free and doesn’t cost anything: at last count there were more than 103,000 visits and still climbing

The quick and easy way to dump the codes is in there too, and all you need to do it is a paper clip! The first two posts contain all the fixes & updates. At last count there were 24 possible causes and fixes for surging idle/stall problems. I continue to update it as more people post fixes or ask questions.

 

[ratio411]

In theory you shouldn't have any problems going to 93.
However the difference between high and low octane is that the high octane is LESS volatile.
Contrary to what the gas companies would have you believe, high octane only HURTS your car and your wallet unless your car truely NEEDS higher octane. Most people buy it because they 'think' it will help something, but it's just a sales gimmick, and higher octane can hurt more than it helps.

My thoughts are that IF you have this much trouble, and it is because of the lower volatility fuel, then you have other issues.
I wouldn't jump directly to that conclusion though, it's probably more likely you got into a bad batch of fuel.