It’s apparently a pretty quick job to remove the EGR valve, 1/2 hour labor to replace, so that might be a pretty good approach just to remove it and see if it or the sealing surface is gunked up or not.
The flexible steel pipe that supplies the EGR and the connection at the exhaust manifold are prone to get blocked with carbon and the EGR solenoid is prone to bleed vacuum opening the EGR. And of course the EGR flow rate sensor is notorious for failure also. Codes P0301 and P0401 are usually connected to one of more of those failures.
I find being out glibbed shameful enough among my equals but by a young lady… I may never live it down.
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well p0300 is random misfire and the 301 305 are telling you what cylinders are doing that. i would look at the coolant temp sensor. most have 2 one for the gage and one for the egu. if the coolant sensor sees to cold temp it acts like the chokes use to do. and enrichens the mixture. and that causes the black smoke. if that sensor fails the ecu interprets or defaults to cold engine starts. not hard to find that sensor if you research it for your truck and to replace more than likely an adjustable wrench and your good to go. but that sensor also should toss out a code.
p0401 is egr restriction but i think that is from the cause of the black smoke or what is causing that. egr valves do not usually cause rich mixtures. your egr valve has 1 port and is then spring closed it may be possible that the return spring broke. but i don’t think that is causing the rich mixture.
as stated bad gas can cause the injectors to mess up but most of the time they do not stick open they stick closed. i have had that a number of times in repairs to other peoples cars, never had one stick open. but have had lots of coolant temp sensor cause your symptoms. a stuck fuel pressure regulator seems that all plugs would be fouling out. you can test the egr with a vacuum type tester if you have one. good luck let us know
Symptoms of a Bad or Failing Coolant Temperature Switch (Sensor)
Common signs include poor fuel economy, black smoke coming from the engine, engine overheating, and the Check Engine Light turning on.
If the ECT sensor or associated wiring has failed, you may see some of the following ECT sensor DTC trouble codes: P0115 - P0116 - P0117 - P0118 - P0119 - P0125 - P0126 - P0127 - P0128
Read more at: https://www.obd-codes.com/faq/ect-sensor.php
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check it out and see if your getting these codes