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Senior Member
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Join Date: Apr 2020
Location: Monroe, WA
Posts: 2,187
Real Name: Devan
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Senior Member
Join Date: Apr 2020
Location: Monroe, WA
Posts: 2,187
Real Name: Devan
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As said P0171 is more than likely a dirty MAF or vacuum leak. Given that P0300 means two or more cylinders are misfiring, and if it doesn't go away with P0171, I'd start looking at your coil packs/lightning hoses - our vehicles use waste spark ignition so each cylinder is paired with another, and off the bat that already sounds to match the issue. Could even be the sparkies themselves, when were they last replaced? Regardless I'd try and tackle this code second of the two.
To test for vacuum leaks simply spray some carb cleaner around the engine bay and listen for an idle change. It can either increase or decrease (though it will typically increase.) Most the time it's either from a cracked hose or a poor seal around the plenum.
It won't be caused by your AF/O2 sensors, as they throw totally different codes.
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