I'm going to lay everything out on the table of the problems I been having with my 2001 jeep Cherokee sport 4.0L. I keep getting misfire codes PO300,301,303,306 and PO135 which is Bank1 Sensor 1. I replace the 1,1 sensor and reset the computer and PO135 went away. Thought that would solve my rough idling. But, I still get rough idling and the codes came back and engine light flashing. Then, I replace the fuel injectors with the Bosch 4 hole cleared the computer and still rough idling misfiring codes came back. I just changed the spark plugs again and still rough idling and misfires and I got same PO301 and a pending PO141 code and I'm sure more misfiring codes are sure to come when I drive the car longer. I ran a CarMD report about a year ago and the report said I should replace my valve springs which I kind of ignored. And, I can not keep any coolant in my coolant tank and have to put some anti- freeze in about every 2 weeks to keep some heat. And I see what look like some chocolate in my oil which I read about on this forum. Is this a sign of a cracked cylinder head is this what causing my misfires and the engine to run rough. Its like I have no power. I pulled the spark plug out on cylinder1 and it looks like it has oil on the end of it. Here is a Pic. sorry for the long paragraph. Thanks! in advance.

 

if your oil is looking like chocolate milk, then that is a sure sign of the head being cracked or he head gasket being compromised. the heads usually crack on those years between the cylinder 3 and 4. if your number 1 plug looks like that it could be the head gasket. I would not drive it until you get it looked at.

 

I wouldn't drive it until it is fixed either. Coolant is obviously getting in to your oil, and every time you run the engine, that coolant is just degrading things in your motor. If you keep driving it like that, even if you do eventually get around to fixing the problem, you may find a whole host of new problems, like worn bearings, that will just add to your misery. I'd get that head pulled and determine if you're dealing with a cracked head or a blown gasket, and deal with the problems accordingly.

 

I been driving it for a while before I started getting the misfires, hope I didn't damage anything else.