GF pulled some codes on her XJ, what to look at first?

Here is the codes that were pulled:

62 - EMR miles cannot be stored in memory
52 - Sustained rich S/A condition
21 - Oxygen sensor signal not switching

This is on a 93 XJ Country with the 4.0 and aw4. The truck has evidently been running rough, and making a funny gas/emissions smell under hard acceleration. I have not had a chance to look at it myself yet, but I am going to switch Jeeps with her and (hopefully) fix it tomorrow. Could a bad fuel pressure regulator be causing this, or would a faulty O2 sensor actually make the truck run rough?

"Funny Smells" could mean bad catalytic converter.

The computer is getting no voltage reading from the o2 sensor and the computer is adding more fuel trying to get a reading. Replace the o2 sensor.

JoBo

Go look at a ring...

A girl who will 1) notice a problem with her vehicle that doesnt involve not starting or flat tire(s) and then 2)be proactive/resourceful enough to either check the codes or have them checked by someone( i assume for free) without getting sold service and parts she doesn't need.

thats one's a keeper...