You Won’t Believe What Causes Your P0304 Code to Trigger!

Thu, 16 Apr 2026 21:45:16 +0000

You Won’t Believe What Truly Triggers Your P0304 Code — Here’s the Surprising Reason You’ve Been Missing! If your vehicle’s ECU keeps throwing a P0304 code, you’re not alone — but the causes might surprise you. Typically, misfires in cylinder 4 (P0304) are assumed to stem from spark plugs, ignition coils, or fuel delivery issues. However, beneath the surface, there’s a lesser-known but highly impactful culprit that many mechanics and DIY enthusiasts overlook: intake manifold vacuum leaks — especially at the intersection of the 4th cylinder and its associated components. ### What Is the P0304 Code? The diagnostic trouble code P0304 indicates that cylinder 4 in your engine is misfiring—producing less power, rough idling, or poor acceleration. Common fixes include replacing spark plugs, checking the ignition coil, or inspecting fuel injectors. While those steps are valid, many P0304 codes persist, leaving drivers confused.