Pontiac Repair: 91gr.prix se 3.1 -no-start, halogen light bulb, radiator core

Question
noticed intermitant rough idle for acouple of weeks. died on cold start.F.P.runs 45psi at rail.no codes.scanner reads 400rpm while cranking.all coils fire to plugs.no inj. pulse.tried known good computer.all fuses check good.Any ideas?

Answer
Hey  Tom. it could be 2 things that come into mind... #1 it could have a bad ignition module and that crank RPM you see is just a substitute value which is kind of unlikely. the other thing is if memory serves me because that's an older model..... the main wire harness that runs under the radiator core support there is a dip in that harness towards the right side and water/road salt condensation has a tendency to collect in that harness and it gets into the wires and corrodes them. If you have access to a service manual  I would check the power and grounds to the ECM. both battery constant power and switched ignition power. I want to say it was usually an orange wire maybe 20 or 22 gauge wire. Check the power feeds but NOT with a volt meter. Use a halogen light bulb or a test light with an incandescent bulb to load down those power feeds. My guess is that you have either a broken wire altogether under the radiator or excessive resistance in one of those power feeds. Good luck. :)