O2 and EGR codes reoccurring | Ford Explorer - Ford Ranger Forums - Serious Explorations

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O2 and EGR codes reoccurring


New Member
December 22, 2020
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Year, Model & Trim Level
2002 Ford Explorer 4. XLT
Hi all, I just completed a engine replacement on my 02 Ford Explorer XLT 4.0. Runs and drives great when cold, but once it warms up a couple different codes pop up. When they appear, the engine stumbles when idling to the point that it kills itself. Occasionally, it will hesitate and stumble when attempting to accelerate from a full stop. The codes in question are P0156, P0135, P0155, P0161, and P1409. Before the engine replacement, I did have a persistent code for one of the O2 sensors, but I ignored it because the car ran fine and O2 sensors are not the cheapest. I have no blown fuses, and the EGR valve itself is new, EGR tube is clean. EGR solenoid has correct resistance as per Haynes manual.

I am at a loss, what could cause it to run perfectly fine when codes are cleared, but be stumbling and gutless once the codes kick on?

Thanks in advance, you guys have helped me a bunch already!