I have a 2000 Cherokee sport purchased about a year ago. A few months after buying the check engine light came on and reported a cylinder misfire. Changed plugs, and problem went away. 6-8 mos later check engine light comes on with a diff cylinder misfire. This time the check engine light was flashing and the jeep was chugging until I got up to speed. When changing the plugs this time I notice the plug from the misfiring cylinder (6) was very dark compared to the others. I didn't see any oil on it or smell any gas. After the plug change this time the problem still occured. I changed the coil rail, and she ran better than ever for me for a few weeks, the out of the blue the problem was back. Help???

A few side notes:

Seems to run fine (light is on but not blinking, and no chugging) when I start her up in the morning or cold.
After my hour drive on the highway to work if I come back within a few hours the light does the blinking thing, and she chuggs along. It seems though that if she has all day to cool down she will run fine home.

The temp guage stays around the halfway mark, and never indicates that she is overheating.

The radiator is always full, but on occasion I notice the res tank for the coolant gets low.

 

I have a similar problem with my 2000 XJ. However, when my engine light starts blinking (codes are reading cylinder 4 and 6 misfires, and random multiple misfire) it does not chug, feel, or sound like it is misfiring, struggling, or loosing power. I have replaced all of the spark plugs and boots last weekend and the problem still persists. Did you ever find a solution to this problem?

 

A flashing check engine light indicates a serious misfire, which if ignored, will eventually destroy your catalytic converter.

2000XJhunter, I would start by verifying fuel pressure. For an 00, you should have 49 psi, plus or minus 5 psi at the schrader valve on the
fuel rail. There are a number of possibilities, but for random misfires, I always like to rule fuel pressure in or out early in the process.

You can rent a fuel pressure gauge from many big box parts stores.

 

I have the exact same thing going on. I know about and am familiar with heat soak but this seems to be a little more serious because it seems to chug even after the heat soak wears off.

Any further help from anyone..?

 

Check the compression in the misfiring cylinder. My Ford Taurus has a cylinder 2 misfire on it and the compression is only 90 compared to the other cylinders of 125. Either a piece of carbon is stuck in the exhaust valve or you have a burnt exhaust valve. I haven't torn apart the Taurus yet to see what it could be. Either way, stop driving it or you will have to replace you catalytic converter.

 

The "chugging" you are referring to is called limp-in mode.

 

my 01 did the same thing a few weeks ago.i changed the injector on the misfiring cylinder.worked for me....has not happend since...

 

I had the same problem with my old jeep .... Did a major tune up still had a po300 code random misfire ran some fuel injector cleaner thru the fuel rail be sure to block off the return line so the chemical doesnt flow back to the tank and pull the fuel pump fuse/ relay depends on the system u use.... that took care of my misfire....