Less than 92 octane = check engine soon, what's wrong?

Hello:
whenever I fill my Chevy Lumina '97 with anything less than 92 octane, it starts pinging, "check engine soon" is blinking. According to the manual,
even 87 should be OK. What might be the problem?
Thanks
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buildup in top of cylinder. Years ago I used to slowly add water to carb intake at high idle to blow out carbon, there is a possibility for carbon to lodge on exhaust valve and burn.
Rey
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When the light is on - take it to an AutoZone and have them read the codes. Then you will have an idea of what needs attention. Anything else is speculation. Are there any other symptoms/irregularities like smoke, hard start, hi temps, etc?
PoD

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Seems to me it's time to blow the crap out of the cylinders.
mike hunt
bat wrote:

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Your check engine light comes on because the knock sensor is detecting the pinging and even retarding the timing doesn't help. The compression in your cylinders is too high. I am sure you just have to clean those carbon deposits out. There are many products out there you can use. Just go to the autoparts store and ask to the (hopefully) knowledgable person behind the counter about your problem, they should be able to get you a good carbon cleaner (with instructions) for you engine.
- JR

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Carbon buildup can cause that much of a compression increase so as to cause those symtoms?

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