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Discussion Starter · #1 ·
Well I tried researching some threads on here about spark knock. So my car has some spark knock, you can feel the timing retard some when it happens so I assume the knock sensor is doing its job. Now I have a stealth CAI and AR103's gapped at .57. So tonite while changing my oil I went back to 104's same gap, took her for a spin, same thing. Its not bad, it only happens when you step on the gas part throttle say at 40mph. I didnt notice this last summer and i had the factory plugs in, I also live at an altitude of 4700 feet. Could it just be the heat?. I fact the last 3 fords that ive owned have done this.[scratch]
 

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Thin air, try a tank of midgrade at the next fill up. My ranger had the same issue, started running mid-grade gas and that stopped it. Im in Las Vegas at around 2500 ft, not as high but combined with the almost 0% humidity and high heat I would get spark knock. Hope that helps!
 

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Try the next higher grade fuel............unless you already run premium. These cars can see some knock on 87 octane even though the owners manual says 87 octane regular is all thats needed.
 

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Discussion Starter · #4 ·
Ill try some 87. Here in Idaho gas starts our at 85. And you can get it ethanol free.
 

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If you were using 85 octane, that is why you are having knock!. The Duratecs are 10:1 compression are and calibrated to run on 87 octane regular grade fuel, not 85 octane.

Mild spark knock will not imediately kill a engine, but over time will take its toll. Trying to save a $1.00 or so on a tank full could cost you more money later.
 

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If you were using 85 octane, that is why you are having knock!. The Duratecs are 10:1 compression are and calibrated to run on 87 octane regular grade fuel, not 85 octane.

Mild spark knock will not imediately kill a engine, but over time will take its toll. Trying to save a $1.00 or so on a tank full could cost you more money later.
Your partially right, yes ford recommends 87 but at altitude the requirements for octane drop. At sea level your typical low grade gas will be 89 octane, in Las Vegas (2500ft) its 87 octane, in higher places like Denver it will be 85 octane or less. Hope that helps.
 

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Discussion Starter · #7 ·
I lived in LasVegas for 11 years and I do remember the gas started at 87 octane. I put in some 91 this morning since my tank was almost empty and ive driven about 20 miles and it seems to behave better. I'll probably go back to a lower octane once winter hits.
 
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