Logan II: Flashing Check Engine Light & Rough Idle

What a flickering light usually means

On your Logan II, a check engine light that flickers — especially at idle or under light acceleration — is often the ECU reporting a misfire. Rough idle backs that up. A steady light says “I have a fault”; a flashing or flickering light says “stop ignoring this,” because unburned fuel can overheat the catalytic converter. Don’t assume it’s just a sensor; start with a proper OBD scan and note any codes like P0300, P0301–P0304, or fuel/air codes.

Check these first

• Spark plugs and ignition coils — the most common cause on petrol Logan II models. Look for worn plugs, oil or carbon tracking, cracked coil towers, or a coil that fails when hot.
• Intake leaks and crankcase breather hoses — a split hose or leaking intake gasket causes a lean misfire and rough idle; a smoke test is quick and decisive.
• Throttle body and MAP/MAF sensor — a dirty throttle body or contaminated sensor can make idle unstable, especially if the fault is intermittent.
• Fuel delivery and injectors — low pressure, a clogged injector, or a poor injector connector can mimic ignition misfire. Check fuel trims and injector balance if the basics are good.
• Battery, grounds and wiring — Logan II electrical connectors and earth points can cause intermittent faults; don’t overlook a weak battery or corroded ground.

If the car is a diesel, the same symptoms can come from glow plugs, EGR, injector correction values, or a clogged fuel filter — but the scan-first rule still applies. On any engine, a compression or leak-down test is the next step if the misfire stays on one cylinder after plugs and coils are swapped.

Is it safe to drive?

If the light is flickering or flashing while driving, treat it as a warning to stop or drive very gently to a garage; prolonged misfire can damage the catalytic converter and wash down cylinder walls. If the light is steady and the idle is only slightly rough, a short, gentle trip to get codes read is usually okay — but avoid revving hard, towing, or ignoring it. When in doubt, park it and get it scanned; a cheap scan now can save a costly converter later.

This material is AI-generated and for informational purposes only — it does not replace an in-person diagnosis by a qualified mechanic.