It had number 4 misfire and low compression on that cylinder. Never overheated. Car ran rough for a while. Car is apart and the head is at the machine shop. I did some online searches and it appears to quite common even on low mileage PT`s. Just looking for ways to try and prevent it from happening again. By the way, we had a 03 Neon with a 2.0 with 168,000 on it and it never had any internal engine problems.