Need Help

My son has a 95 Wrangler/Sahara w/120000 miles. Recently two things have started happining. After driving for about ten minutes the check engine light comes on and also when driving there is a smell of exhaust in the vehicle. The check engine light does not come on when the vehicle is parked and idling only when driving. Any ideas on if this is a oxegen sensor problem or something else. Recently had a new muffler put on and am not sure if the smell and light were happining before. My son is overseas in the military and I cant get ahold of him to ask. Thanks!!

Just replace o2 sensor and see if light goes away. Exhaust in cab of jeep is not good, 1995 probably rust hole somewhere, fiber glass it up.

With that many miles, you may want to check the catalytic converter. Does the Jeep seem to lose power at higher rpms? If so, the cat could be clogged, reducing exhaust flow and leaking out somewhere and into the interior. Does the smell happen right away, or does it take several minutes to manifest? If it's not the cat, then an exhaust system check is in order.

Canamark is right about the O2 sensor; it could be that, or it could be that after 10 mins the cat is clogging/backing up and causing a bad reading.