[QUOTE=KD3NE;1494328]

If so I thought that was indicative of a somewhat serious misfire condition?

I'm not certain but I think I read that one some threads here before.

^^^^ GM does that. It's flash city if you break a spark plug wire or any other misfire condition

 

It comes on and goes off after an hour of driving or so. It comes on again after a few days.

 

It's amazing what new spark plug wires and plugs can do. Jerking when pressing gas has stopped. Hesitation and backfire when accelerating has stopped. The idle sounds more powerful and you can feel how much less you press the gas pedal at any speed.

 

Ha! We go all tecky to the "Nth" degree, and it sounds like it was the plug gap! .. Gonna need to remember this one.

 

what is all these codes mean and what is the purpose what do they stand for
I have a 2007 Cherokee Laredo cannot get the codes by turning key on and off three times does not show no codes how do I get to it don't even have a button to reset the mileage button does not have cannot find how to get codes anyone got any answers

 

I had a similar issue with my 99, ran fine, drove fine but had a rough and stumbling idle and check engine light every now and then with no codes. I cleaned my idle air control valve, because I never did so to no avail. After running it and noticing my fuel mileage decreasing significantly I decided to dig a little deeper. Turns out that it was my upstream oxygen sensor being a bit lazy and causing my motor to run rich. Not really noticeable above idle but as it got colder out I was able to smell more and more fuel and my fuel mileage dropped from 15 to about 9 so I immediately picked up a pair of oxygen sensors both upstream and downstream and my issues are resolved I’m now actually getting 16 miles per gallon. Probably didn’t need to replace the downstream one but thought I might as well since they were both original

 

You're in the wrong group. This is for the 84-2001 Cherokees. I assume you have have a GRAND Cherokee, so you'll likely get better information over in https://www.cherokeeforum.com/f5/ instead.

That said, you will need to buy an OBDII code reader and connect it to the diagnostic connector under the dash to pull codes, which you can google.

 

Update in 2022:
Also had this issue and had success with the upstream O2 sensor replacement!