Q: For last 3 months I was driving the car once a week for around 30-40 miles. Bought it an year ago (52k), now it has 63k. A couple weeks ago the CEL came on. Stopped by local Autozone to have it checked - the guys said the fault code was reading 'random cylinder misfire' (didn't specify which one). Then I went to audi dealership, where the tech explained that this is due to not driving the car(??) regularly. They cleared the code, but a week later, it came on back again. Another week later the CEL flashed for a few seconds with engine still idle, then turned steady again. Can feel some stuttering, kind of hesitation of the engine, usually when engine is cold. While driving (light on) everything seems to be normal - power, no shaking feeling, good mpg... Any ideas? Thanks
A: Hey, to be honest it's very hard to diagnose a car without looking into it. But, as far as the last guy said replacing the coils. Don't do it. It is very unlikely that more than one coil would go bad at a time. With that said if your getting a random cylinder misfire this states your having a problem with more than one cylinder (obviously). So, chances are your coils are fine. I'd have to take into consideration of what the audi tech said. So, from this I'd say since your driving the car for short periods once a week there is a good possibility that your spark plugs aren't heating up enough (staying too cold) to effectively burn off fuel and carbon deposits. Therefore, your spark plugs are fouling out and not igniting the mixture which is causing the random cylinder misfire. This is why you feel it the most when the engine is coldest. Solution: If you plan only on short trips with the vehicle... Get some new spark plugs, but ask for a hotter plug. What this plug does is, rather than dissipating the heat generated by the spark plug into the cylinder head like normal. The plug is designed to retain the heat it creates to burn ""hotter" hence the hotter plug. This will burn off any carbon deposits and fuel in a short trip that the normal plug doesn't have enough time to heat up for.