Flashing CEL and Rough Idle Signals VW Misfiring Issue

Had the same warning light issue on my 2004 VW Golf with the 1.6L gas engine. The flashing check engine light combined with rough idle typically points to a cylinder misfire, which often gets misdiagnosed as a knock sensor problem. In my case, the ignition timing was off due to a failing ignition coil pack. The symptoms match exactly, engine knock during acceleration, increased fuel consumption, and unstable idle. The repair involved replacing two coil packs and spark plugs. The fuel efficiency dropped about 30% before the fix. This is a serious issue that needs immediate attention since continuous misfiring can damage the catalytic converter. The diagnostic scan showed error codes related to cylinder 2 and 3 misfires. Important: If the check engine light is flashing rather than steady, reduce driving to absolute minimum until fixed. A flashing warning light indicates active damage occurring to engine components. The common wear pattern on these VW engines often shows these symptoms around 140000-150000km, matching your vehicle mileage. Worth checking the spark plug condition first, they can indicate if coil packs are the likely culprit.

Thanks for sharing your experience with the Golf ignition system troubles. The symptoms with the warning light and poor performance match exactly what I noticed too. Auto repair prices can vary so much, mind sharing what you ended up paying for the coil packs and labor? Just want to get a rough idea before heading to the shop. Also wondering if you had any other ignition timing or performance issues pop up since getting it fixed? My VW Suran is still running a bit rough even at idle, so trying to figure out if I should expect other related problems.

Thanks for asking about the repair costs. Actually, when I took it to the shop, the malfunction indicator and poor performance turned out to be from a defective knock sensor after all, not the coil packs I initially suspected. The mechanic found a damaged cable connection to the knock sensor that was causing the engine knock and rough running. The fix was surprisingly simple, just 95€ to repair the faulty wiring connection. Since getting the knock sensor issue sorted, the engine runs smooth and I havent experienced any additional performance problems. Fuel economy went back to normal too. When the sensor isnt working properly, the engine management system cant detect and adjust for knock events correctly, which explains the rough idle we both experienced. Its a good reminder that similar symptoms can have different root causes, even in similar VW engines. The car has been running perfectly for months now with no warning lights or poor performance issues. Getting a proper diagnostic scan really helps pinpoint these problems rather than just swapping parts.

Thanks for the input. I took the car to a trusted mechanic yesterday and got it properly diagnosed. Turns out it was actually a cracked vacuum line causing the rough idle and check engine warning light. The mechanic showed me where the line had split near the intake manifold. The repair only cost 165€ including parts and labor. The fuel efficiency is already much better and the engine runs smooth again with no warning lights. Such a relief it wasnt something more serious like coil packs or timing issues. Really glad I got it checked quickly when the malfunction indicator first appeared instead of driving it longer with the problem. The mechanic mentioned driving with vacuum leaks can cause additional engine performance issues over time. Looking back, getting proper auto repair diagnostics first saved me from unnecessarily replacing more expensive parts. Will definitely keep monitoring for any changes in how it runs, but so far everything seems back to normal.