Is there anything specific I should be watching for? I'm a little bit of a rookie with electronic diagnostics.

 

When warm, they should switch from .1 to .5 volts very rapidly.

 

can you provide a link to your Bluetooth OB2 scanner? lol that sounds cool. i need to start doing some shopping for one.

 

Google ELM 27.

https://www.google.com/webhp?sourcei...F-8#q=elm%2027

 

Well, the o2 sensors read normal as far as I can tell. I flushed my heater core Monday night and my coolant looked like muddy water almost. A lot of sediment came out of he heater core and my coolant smells burnt. I am also getting a pretty strong burnt coolant smell with the heat on.

Every bit of research I've done is pointing at a blown head gasket. I am going to the auto parts place tomorrow after work to borrow an exhaust gas tester and I'm imagining I will be seeing something I don't want to. Hopefully it hold out until next weekend and I can take Friday off of work and get started on that. My jeep is my only vehicle, so I will have to work through the entire weekend to get it done.

You win some, you lose some I guess...

 

if the head gasket was bad you'd see it checking the oil or you'd have low/no coolant

 

I'm not losing coolant very quickly, but I know it isn't in my oil. From what I understand, it is very possible to have the head gasket fail between exhaust and coolant runs without coolant ending up in your oil. It just cooks the ever living **** out of your coolant, causing the coolant to break down and essentially boil the water off. If it wasn't well below freezing, I'm sure I would have overheated a time or two. I could be wrong, but I guess I will find out later today.

 

You're on the right track.

 

I was afraid you would say that. That would explain the poor mpg, water being burnt into the exhaust would probably throw the o2 sensors out of whack. Is there any way to check the cat for damage from burning coolant?

 

Since your xj is OB2 it should set a code if it has failed, catalyst efficiency monitor it's called. But if you have a temp gun you could go for a drive and get everything nice and hot and measure the catalytic, should be about 30 degrees Fahrenheit hotter at the outlet than the inlet. That is an approximate number, some source's will say up to 100 degrees, which you may see if you've got too much fuel getting through. Either way a temp increase is a good indicator the catalyst is functioning at least.

 

That makes sense. Just figured if I'm sending fried coolant at it, it might have some adverse effects. Guess I won't know till I know.

 

Just a suggestion:
When I did my son's gasket I used a 2x4 stud laid across fender, then 2 short chains bolted to head, one each side- manifold /dist side. Then we just lifted it up and out.

 

Good call. The head weighs what, 85lbs?

At least I'm getting all of the fun stuff out shortly after buying my first XJ....

 

Murder,I would do as suggested and change cap & rotor.
Also, check your brakes. Dragging brakes can kill MPG.
Let us know how the head gasket goes.

 

Will do. I'm sure its a wonderful combination of things causing the poor milage. That's the gamble in buying a vehicle with 190k on it. All looked well when I bought it, maybe the p.o. knew about the head gasket and I was just the sucker to buy it.

Live and learn, this just means I will be driving this jeep until it croaks.