I'm trying to trace the source of bluish/whitish smoke and fumes from my 95 XJ, 4.0, 165K. I know it's probably blowby, but the weird part is that it's only really bad when I'm idling AFTER a highway drive. Around town, even after reaching temp, there's little smoke, even at idle. Drive a while on the highway and then stop at a drive-thru, and it's clouds of smoke. It never overheats; oil pressure is fine, coolant isn't running out.

I've cleaned out the CCV tubes and changed the oil, plugs and plug wires... I'm thinking O2 sensor is the next thing to try. Sound right?

Also, although the temp gauge gets up to operating temp, it never goes past dead center, and usually sits a little below. I'm thinking maybe the thermostat is stuck open... would that lead to smoke from running too cold and thus not burning all the fuel?

Thanks

 

I'v cleaned all the CCV tubes and even installed a bigger vacuum fitting and hose going to the rear CCV. I done all the little tricks your read about online to stop blow by. I have pretty much eleminated it other than after a long highway speed drive. My XJ has 242K miles but, it still runs like a top. Just after a long highway drive, I know I need to open up the intake air tube and wipe it out.