Cracked head?

I have a 1996 Isuzu Rodeo...3.2V6 with 147,000 miles on it. As I was driving it home it began to idle very rough and a knocking sound began. Once home I decided to see if I figure out the problem. As I was listening to the knocking and watching the motor bounce because of the rough idle it stopped knocking and the idle smoothed out, but when it did this smoke began to billow out of the exhaust pipe that smells like burning oil. I also notice that there was some oil dripping out of the spark plug housing. I am having a hard time figuring out why the knocking and the erratic idling would stop and result in turning my rodeo into a mosquito sprayer. I checked with the previous owner and the timing belt and tensioner are fairly new. I did however put some fuel cleaner in my vehicle prior to all of this taking place...don't know if it that might of dissrupted something...I did, however, try to rev the rpms up for a few minutes thinking that the smoke might clear out, but no luck. Any help would be wonderful. Thank you.

Cracked heads/head gaskets are not common on the 94-97 model years, they're more common on the 98-99yrs.

However, what is the maintenance history on the cooling system, has it ever gotten hot? If the cooling system has been neglected in the 147k miles, it is possible to have a cracked head, these engines are all aluminum and it is very important to keep fresh coolant/hoses/etc.

I asked you in your last thread, how much oil is your truck using between oil changes?

Have you pulled your spark plugs yet, to take a look?'

No one here can give you a definite answer without some inspection of the truck itself.

Keep us posted - if diving into some suspects are not comfortable with you, then find a good import mechanic as you may want to stop driving it until you know for sure what it is. If it is a cracked head, you're doing damage every time you start it.

kmcdermett - are you still around?

I've only had the vehicle about 3 months...so I'm not real sure about the exact history of the thing. I bought it from a friend of mine and I'm not sure that he took real good care of it. I changed the oil as soon as I bought it and it never seemed to use any oil. I also changed out a bad thermostat when I bought it and I'm not sure if he ever let it get hot. I have checked the oil since I began to have problems with it and there is no water in the oil....that makes me think that I probably did not crack the head, but I guess you never know with these rodeos. I havn't had a chance to remove the valve cover yet but I'm going to run a compression test on it tonight. Hopefully I will have a chance to pull the plugs tonight as well. Maybe you can give me some insight on the spark plugs on this thing...they seem to have a different housing then most other vehicles. I've got a pretty good mechanical aptitude, but have never worked on a foreign vehicle this new. Thanks again for all the help.

*bad* thermostat, when you replaced it, did you use an OEM Isuzu thermostat - if not, get an OEM Isuzu one ASAP. Any other brand won't cut the chase on this truck, won't keep it cool enough.

Ask your friend if when the thermo went bad, if the engine got hot. Antifreeze doesn't always show in the oil right away.