That is a very characteristic sound. The 3.7 has a couple of known issues and it sounds like yours is suffering from one of them. The 02 in particular had a habit of breaking valve springs. Then the valve doesn't stay sealed and you get misfires. The other side effect is that if the spring fails and the valve is in the way the piston will hit it and bend it just enough that it cannot seat, then it will start hitting it and give a knock like you have. The easiest way to tell if this is the case is to use a bore scope and look inside the cylinder to see the damage. If the top of the piston isn't severely damaged it's possible to just replace the cylinder head with a remanufactured unit and keep driving it. If the damage is worse then it is usually cheaper to swap the engine out with a remanufactured unit or a used one. But be very careful with a used engine, you need to be sure what year it is. Chrysler made changes to the 3.7 and the control systems during it's production and although the engines share many parts they cannot be interchanged as a complete engine. 2002-2004 will interchange as a direct swap. There are ways around that and for that you should look at this thread at the KJ forum -
https://www.jeepkj.com/threads/engine-swap-overview.53270/
The Libby is a fun Jeep and the later engines tend to last far longer, the 02 had what could be described as "teething issues". I had a 2003 that was at 145,000 miles when it was hit and scrapped from the damage.
Sunday, February 2nd, 2025 AT 10:19 AM