98 Blazer with Horrid Ping

I just bought a 98 Blazer with about 70K miles. It runs good execpt for a bad ping problem. I am living at an altitude of just over 9000 ft and I am running hi-octane fuel.
I assume the problem is either with the EGR system or the knock sensor. Can anyone tell me how to check these systems?
I would go down to a local auto parts store and buy a manuel, but since I live in Quito Ecuador, manuals are a bit hard to find.
DRW
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"drw170" wrote:

This is curious, at 9000 ft it dhould not be a problem. What is the octane of fuel down there.
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There are two grades of fuel here, Extra and Super. They don't post the octane rating, but I think Super is 90 or 91. I am running Super, which is what everybody recommends.
I do feel that there is a problem somewhere else. With a computer controlled ignition, the computer should take care of the timing. I drove my Dodge Caravan to the top of Pikes Peak, and other then not a lot of power at that altitude, it ran great. So 9000 ft shouldn't be a problem.
EGR and Knock sensor seem to be the logical places to look, but can anyone tell me how to check them?
DRW
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Since I just purchased this Blazer, I didn't have any hitory to know how it was supposed to run. When I test drove it I remembered a little ping, but not much. The first tank of gas I put in regular just to see how it ran. Not surprising, it pinged badly. The second tank was Premium and it ran about the same.
Most people I talked to seemed to think it was fuel, so for the thrird tank I filled up with premium at a different station (Texico) and it runs like a different vehicle!
So it appears that the problems was bad gas after all.
By the way, one "home remedy" that I was told by a local mechanic here to raise the octane of gas is to put "moth balls" in the gas tank, (1 per gallon of gas). He says that will eliminate most pings.
I am not about to try it in my car, but anybody know what moth balls are made of?
DRW
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"drw170" wrote:

Naptha, it is a very old trick.
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try the library?
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