Hello, I have a Sierra DOHC (120 hp ), 1990 year, 198,000 km mileage. The ignition rings as soon as I accelerate a little bit more. This noise only occurs when the car is really warm. In cold condition the noise is not heard. My impression is that it is stronger at high outside temperatures than at low outside temperatures. The Sierra is definitely fuelled with the right fuel. At Ford you could not explain the thing. It’s just that I’m supposed to keep on watching (I’ll do it too, but I don’t think it’s gonna change anything). Otherwise the engine is running perfectly normal. The ringing hasn’t gotten any worse over time, it’s only dependent on the temperature. Even if the Sierra slowly mutates to the grandpa, I’d like to drive it even longer. I’m afraid, however, that the ringing can’t be healthy in the long run. Maybe one of you has a suspicion. I’m grateful for any advice. MfG Kohl beet