IntrepidBear
NAXJA Forum User
- Location
- Ilheus, Bahia, Brazil
I am stumped on this one, I've tried searching but cant seem to find symptoms that match mine. I hope someone can share some wisdom to get be back up an running!
99 XJ
4.0
mostly stock
Federal emissions
290k miles well maintained
Replaced CAT and entire exhaust including oxygen sensors 2 years ago
Did plugs wires and distributor 2 years ago
Recently replaced entire cooling system
Drained and filled all fluids before trip.
Just got back from ~1600 miles of highway + ~125 miles of trail trip.
Symptoms:
Drives fine on the trail
Terrible highway MPG 11-12 ( I normally get 18-21)
Sluggish on highway, shifts down on any type of grade to maintain 70-75mph
On steep grades in mountains I was struggling to hold 55mph getting dropped by big rigs, shifting into 2nd and doing 4000rpms!
I also noticed the temp starting to creep up on very long stretches of uphill
I recently failed CA smog with high NOX @ 15mph
I suspect the CAT might be partially plugged, how can I test this?
Could it be a fuel pressure problem? I've never replaced the fuel filter, on this model I think that they might be integrated into the tank or pump.
Anyone else had these problems? I don't mind spending a bit of cash to fix it, but I don't want to start throwing parts at it without first hearing from others with same symptoms.
Thanks All!
99 XJ
4.0
mostly stock
Federal emissions
290k miles well maintained
Replaced CAT and entire exhaust including oxygen sensors 2 years ago
Did plugs wires and distributor 2 years ago
Recently replaced entire cooling system
Drained and filled all fluids before trip.
Just got back from ~1600 miles of highway + ~125 miles of trail trip.
Symptoms:
Drives fine on the trail
Terrible highway MPG 11-12 ( I normally get 18-21)
Sluggish on highway, shifts down on any type of grade to maintain 70-75mph
On steep grades in mountains I was struggling to hold 55mph getting dropped by big rigs, shifting into 2nd and doing 4000rpms!
I also noticed the temp starting to creep up on very long stretches of uphill
I recently failed CA smog with high NOX @ 15mph
I suspect the CAT might be partially plugged, how can I test this?
Could it be a fuel pressure problem? I've never replaced the fuel filter, on this model I think that they might be integrated into the tank or pump.
Anyone else had these problems? I don't mind spending a bit of cash to fix it, but I don't want to start throwing parts at it without first hearing from others with same symptoms.
Thanks All!