P0300 and P0171 Together With Rough Idle: Why This Combination Almost Always Means a Vacuum Leak
When your scan tool shows both P0300 (random misfire detected) and P0171 (system too lean, Bank 1) stored at the same time with a rough idle, you are not looking at two separate problems. You are almost certainly looking at one problem: a vacuum leak. The combination of these two codes together, specifically at idle, […]