Exhaust leaks are all too common on the 3.8L. The main culprit is typically a cracked exhaust manifold. Unfortunately, this isn’t a one side or another issue, so plan on replacing both. A cracked exhaust manifold can cause the Jeep to run poorly and eventually lead to trouble codes. It can also be misdiagnosed as an internal engine problem to the untrained ear. Before you go too far into the engine diagnostics, be sure to peel back the heat-shield covers and see if your manifolds are toast.