Land Rover Repair: 98 Disco Check engine; problem w/ O2, poor gas mileage, o2 sensors

Question
98 LR Discovery SE V8; regular petrol.
My vehicle has recently had a new catalitic conv. installed. Problems:  ck engine light on intermittantly; idle is irregular; cked @ local station and was told 02 sensor(s) malfunctioning; very poor gas mileage and vehicle sometimes smells of exhaust fumes.
What's wrong and should this problem be handled only by the dealer?  Thanks for any help!  cb

Answer
Hi Chris,

all this happened right after your new cat's were installed?  Did you replace the Y pipe with an aftermarket copy, an OEM or did you rig up something else?  When the O2 sensors were removed (or replaced) were they damaged?

It may very well have been damaged sensors that are causing these problems.  Check to make sure they wires are connected properly to the O2 sensors.  Perhaps no signal is being sent.  Do this when the engine is very cold.  I need only to remind you once. :)

Where did you get the Y pipe?  Did you have a garage install this or did you do this yourself?

So far, it sounds like the problem is isolated to just these components and they are easy to repair in most garages - even yours.  When they install the O2 sensors, I would have used an anti-seize dope on the threads.  Seals it well but lets you remove them later - with a bit of effort.  I would think bare threads on an exhaust pipe is a recipe for a permananent connection.  Not good.

Best of luck,

JohnMc