PO300 on 2006 Chevy HHR

Question

Replaced plugs, coil pack and ICM. Car was perfect after replacing parts until cool down then the ruff idle and flashing check engine was back. Replaced coil again and AGAIN it ran perfect until cool down. Any ideas?

Answer 1

P0300 Random misfire

Anytime the CK ENG LT flashes this is ignition related,Check the sparkplug  wrong type or wrong application will cause the code condition which tends to be overooked.