So my 1999 XJ has a couple issues…

First, the engine seems to be running a little rough. It has a light sputtering sound to it. The engine seems to lack power when stepping on the gas. My hunch is that a cracked exhaust manifold is causing the problem. Sound right?

Second, the temperature gauge when in gear never gets above 150º and that's running in Texas on a hot day. However, when I put it in neutral the temp gauge goes up and reads a little above 200º. Thinking this could be a thermostat?

Any chance the two problems are related?

Thanks for any help.