Question

Have 1999 Volvo S70 Non-Turbo. Codes are P0420, P0645, P1004, P1081, Symptom= intermittent stall.

NO Check engine light on. Seems to accelerate somewhat before slowing when the accelerator is released.

Answer 1

the problem might be caused from P1081 which is related to the key immobilizer key. replace the key battery first.

if that does not help you might need a new key and have it programmed or the computer is bad 

try to fix P1081 first.