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Dramatic increase in spark knock after trip to high altitude

traxtion

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I live at around 5400 feet and run 87 (premium here) to avoid the spark knock that comes with the 3.6. Came down from a two day trip at 12,000 get today and filled up with 87 and the engine is now knocking like crazy. Just threw in a bottle of STP since the noise drives me crazy but I’m curious… did changing altitude by 7000 feet confuse my ECM? Or am I more likely to have gotten a bad batch of gas.

Was also getting a high speed rattle that sounded closer to the dash then the usual knock when accelerating in third at high altitudes today.
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Left Field

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What has your oil consumption looked like?

Any oil that goes through the engine can leave carbon deposits which can result in rapid onset detonation. I learned about it on my previous Jeep due to a small intake plenum leak that was drawing air & oil vapors from the crankcase.

Not a ton of oil usage, maybe a quart every 1500 miles, but a lot of pinging. New intake plenum gasket and some carbon remover => bingo - back to not adding oil between changes and no more pinging.

PCV valve, overfill of oil, plenum leak, etc. - there are a number of things that could cause the same effect.

That's just one possibility of course. Might just be bad gas.
 

Chupacabra

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I live at around 5400 feet and run 87 (premium here) to avoid the spark knock that comes with the 3.6.
Where are you in Colorado where 87 is premium? I've never seen premium labelled any lower than 91 here. Every station I've ever seen in Colorado has 85/87/91, or 85/91 if no mid-grade.
 

FWB FL

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Just came from Colorado, 12,500 feet in the Rockys with no noise from the engine up top for a week or back in Florida at sea level. Did use one tank of 87 while there.
 

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areuriding

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Bad gas, run it empty as quick as you can. Put in an additive like BG44K then fill up.
 

LooselyHeldPlans

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Where are you in Colorado where 87 is premium? I've never seen premium labelled any lower than 91 here. Every station I've ever seen in Colorado has 85/87/91, or 85/91 if no mid-grade.
To me, anything above the lowest grade offered is premium by definition.

87 is not the lowest grade offered where I bet 95% of the state population lives.
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