1995 XJ Cherokee missing

[Glenn]

oxygen sensor is down on the exaust on the left hand side just below the exaust manifold, I don't know how or if it can be tested, someone here may, when mine played up the check engine light came on and the code it displayed said nothing about the oxygen sensor, even hammond jeep were stumped as to why my car was running rough, thanks to some help on here though I ended up changing the sensor myself and all came right, for about $150 for the sensor it all ended up cheap enough. By the way you can't usually see anything when your spark leads are stuffed, cracks etc. if they're old just replace em.

[Gojeep]

You can get cheaper 02 sensors from Bursons or Repco etc and get the NGK ones which are better than stock. They should be changed at 132,000 kms. Are the leads in the proper holders as cross fire problems on these are a real problem if not? Happens a lot when non dealer leads are used as they dont fit into them. The dealer leads should have Mopar written on them and be either red or black. Red is no longer sold and mean they are old enough to be replaced if you have them. Change you cap and rotor at the same time using only dealer parts and have had the same problems you have by using aftermarket ones.
There is no such thing as a one digit code so you did read them correctly. 12 just means the battey was disconnected in the last 50 key on cycles and 55 means end of codes so they dont help you at all.

[dpalmer]

I had a similar problem and it wasn't til it started doing it at idle one night. I popped the bonnet and could see the arcing from one of the leads to the engine block. The leads looked fine until I looked VERY closely. Replaced them - no more arcing and no more power fluctuations!