dear god please help...98 2.0 I4 5sp.

[andobone]

ready to pull my hair out.
have a 98 venge, 2.0 I4 5sp. real rough idle at start-up.....when driving idle remains between 2100 and 3100 rpms until 3mph or less where as it will retun to its normal 1100. idle will surge when clutch is depressed if lower than 2100 rpms and car is moving greater than 3mph.
Also....engine will overheat at idle, but return to normal operating temp. when driving.
Noticed a reduction in gas mileage.....tail pipe has turned stone black.

any ideas??? don't know where to begin.

[BleedDodge]

Catalytic converter might be plugged or plugging. Black tailpipe makes me think that.

[andobone]

are there any tests that can be run to determine that?
or do i just have to replace the converter and see what happens.

[rksnc]

yes the muffler shop can run a back pressure test to see if cat is stop up.