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Car os a 2016, 150k miles. Check engine light keeps coming back with the codes P0300-5, random misfire on various cylinders. The coils have been replaced 3 times, apparently needlessly, over the past 2 months but the check engine light will come on again after a few days of driving. The VW dealer can't seem to figure out why. At one point the alternator was putting out only 11 volts so it was replaced and they thought that was the issue, but no, the codes came back.
I'm at a loss and the dealer is no help. Car seems to run okay but I don't want to ruin the cat if the car is truly misfiring. Walnut blasting had been done but it didn't seem to help. Anyone have any ideas? Please?
 

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1st. The most basic thing is to use a higher octane fuel.
2nd. A clogged injector ... in this case, injector #5
3rd. Check the spark plug... in this case, spark plug #5.
 

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Could be a vacuum leak spray some “Brakeleen” the green can one around the intake and valve cover and see if the idle changes. Also have they checked compression on the cylinders or just thrown parts at it?
 

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Check your injectors and injector o-rings. If that doesn't fix it you may think about a fuel rail pressure regulator. After that maybe start checking wiring.....or that where i would start.
 

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Check your injectors and injector o-rings. If that doesn't fix it you may think about a fuel rail pressure regulator. After that maybe start checking wiring.....or that where i would start.
Also maybe on a long shot run some seafoam through it.
 
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