found a web site, auto reference center, that tells you how to test the sensors on your vehicle and see if they are working right. The egr solenoid valve was bad, the map sensor was bad, the oxygen sensor was bad and the knock sensor was also bad. But this engine continued to run but the ECM never showed a code. The only thing I can think of that might of happened is the ECM went into limp mode so it could continue to run or the ECM is bad, I have a OBD I, any other thoughts