Need help! I recently purchased a 2006 Doge Dakota with a 3.7 litre V- 6 engine with 17,000 miles. There is a ticking sound coming from under the plastic manifold on top of the engine at idle. Does anyone know if this is normal or some kind of valve tap? Also, the engine seems to wonder in RPM's like a variable idle speed...not much, but enough to hear and see it on the tach as the needle just hovers a little above and below 700 RPM. Any input would be appreciated.