P0400 is a fault with the EGR system but from your description of the symptoms, it should not be the cause of the problem. Your main issue should be the idling system.
Usual fault with the idling system would be dirt clogging the air passages of the IAC and throttle body, were they cleaned? You mentioned resetting the IAC, how was it done? If the IAC and throttle body is dirty, resetting the IAC by means of clearing the memory would more likely aggravate the problem.
How was the throttle cable adjusted? There must be sufficient slack of the cable, otherwise the idle would not be stable as the throttle would not close correctly.
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Sunday, April 15th, 2018 AT 2:52 AM