Q: I had a p0405 get code replaced egr valve, map sensor,mad sensor, and PCv valve just to be safe but still getting the code why?

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I had a code pop up for egr system p0405 the I also had a mass air flow code. To be on the safe side I ordered all brand new parts with a few extras to be safe as following. The egr valve components, the maf sensor, a map sensor, and a PCv valve installed and reflashed codes car runs good now no hesitation or stumbling whatsoever. But when I turn it on it still lopes and idles at a low rpm 500 or so. What do u guys think it might be? I also keep on getting the p0405 and already checked voltage and it is good

My car has 170000 miles.
My car has an automatic transmission.

The code P0405 and a rough idle is most likely due to carbon getting into the EGR pintle. This will hold the EGR open. When you are getting the rough idle you should shut off engine and remove EGR valve. Check to see if carbon is holding the pintle open. If it is then you will have to remove the carbon from the pintle. Then try and clean out the EGR passages by scrapping them using a round wire brush. Afterwards, start the engine for a few seconds with valve removed to blow out loose carbon. You should then spray a small amount of carbon cleaner into the passages to dissolve the carbon. Lastly, reinstall the EGR and reset the light and codes.

If you’d like assistance with this, consider YourMechanic, as a certified professional can come to the vehicles locations to perform these checks and properly diagnose your Check Engine Light.

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