has anyone ever had this problem?

[mattsan]

My 93 1.6 sentra sometimes runs very rich, and the car hesitates badly when it happens. Sometimes the car runs great, and sometimes it runs like the O2 sensor is bad. I replaced the o2 sensor twice and no difference. If it was the o2, wouldn't it always run poorly? The car when running bad has a bad smell coming from the exhaust, so I thought it might be the cat. but it isn't.I had it checked. Any help would be appreciated. Thanks

[evil21]

Have you checked the throttle position sensor? What octane level do you use?

Also, have you hooked your car up to a computer to find any error codes?

[mattsan]

I use 87 octane. No to throttle postion sensor and computer.I'll see if someone can do that tomorrow thanks.

[evil21]

Did you find anything?