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2001 4.0 Exhaust gasket and mpg

srmitchell

NAXJA Forum User
Hey guys. I have a 2001 xj, CA emissions, AW4, 4 inches of lift, 4.56's, 33's, lots of armor. (So it is heavy.) I used to average about 15, and be able to pull down at least 18 freeway.
It has a cold air cowl snorkel, 60mm TB, high flow exhaust, but for the last year or so, it has been getting a constant 200 miles to a tank. I drive rather conservatively, about 60 mph on the freeway always, and I baby it around town. MPG always sucks.

The bad mpg is killing me. I recently replaced both upstream O2 sensors with NTK units, (the oem part), replaced a faulty temp sensor, cleaned the hell out of the TB, intake temp sensor, and I just replaced the map sensor. The plugs are new dual platinums, the correct part for an 01 with the waste spark system.

I just seafoamed it, and it blew out white smoke from the exhaust gasket like I couldn't believe. Literally white smoke billowing out of the engine bay.

Could this FINALLY be culprit? I imagine a huge exhaust leak would cause a faulty O2 sensor reading, causing the engine to run rich. And also, there seems to be a lot of black soot on my back bumper where the exhaust hits.

Also, I have noticed an exhaust smell in the engine bay, and a ticking sound under load.

Thanks!

Sean
 
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