I just scrolled back through the thread to read your first post about when the problem began. If you washed the engine while it was still hot, there is a small chance something might have warped. It wouldn't hurt to take a straight edge to the bottom of the plenum to make sure it is true while replacing the gasket.

When reassembling, follow the RAVE for bolt torque and sequence.

 

Yup. That's what I got. my guess is warped upper manifold.

Lesson learned - I WILL NEVER WASH MY ENGINE AGAIN.

 

Lol, we need to stop posting at the same time.

 

At least don't wash it just after driving. Let it cool off a little first.

 

I don't understand why Land Rover guys always preach to replace all 4 O2 sensors at the same time.

O2 sensors only effect closed loop tuning. The ECU only uses the two pre-cat sensors to adjust the fuel map. The post-cat while they can potentially throw a CEL, do not have any effect on how the engine runs.

 

I don't. I replaced both of my fronts at 105K not because of a SES light, just because they had 105k on them, and were more than likely not switching as fast as they were when new. The rear sensors will not be touched, unless they throw a code.

 

I'm bored waiting for Breaking Bad to come on, so I figured I'd add my two cents regarding O2 sensor replacement...

As background, I've been using a code reader in conjunction with my iPhone to read and reset codes. I can't recall the two recurring codes but they were the upstream and downstream codes many have cited. I was thinking MAF issues after searching forum, or O2 sensors. I ordered Bosch sensors from Advance Auto Parts (had lowest price with shipping and a coupon code I had).

In the interim, I was driving to beach with my daughter when the truck gave out in Richmond. When I say gave out, it stalled repeatedly, and through this website I diagnosed bad crank position sensor, which I had replaced (thanks, guys!). Next 900 miles, no check engine light or codes...

Got home and received sensors. Herein is the crux of my post- a weekend mechanic (but a degreed engineer) replacing the O2 sensors...

Left rear - busted knuckles and approximately 1 ounce of blood spilled between loosening sensor and undoing connector in a blind state. Maybe one hour of effort. Note - truck was not on lift or jack stands - which would no doubt facilitate this process.

Left front - remarkably easy after slathering sensor with bolt loosening spray. Only swore once or twice in the process...

Right front - connector is readily accessible and I wish I had started here (if only to shorten learning curve). Having said that, sensor itself was basically welded to exhaust, and took a couple of sessions to finally remove. Broke the coolant expansion tank to radiator metal hose in the process, as well as promise to my wife not to use the F-word repeatedly and at volume...

Right rear - ahhh, saved the best for last. The sensor actuaaly broke free with modest effort. The connector, however, is so far up into the nether regions of the chassis, that reaching it with a fingertip is a major feat. This is where I lost approximately a half-pint of blood. Never got the connector separated. I think that, if I dropped the drive shaft, maybe I could do it. Seeing as how the driveshaft (Tom Woods - love it) was recently installed, that wasn't gonna happen...

I wondered why Bosch offered an OEM replacement that included a connector set... Who were they trying to fool? Why would an OEM sensor replacement require a new connector? Answer: When some cockney technician on the assembly line placed the connector out of reach by anyone other than a simian...

Solution: order a Bosch sensor with connector set. Live and learn.

Still don't know whether or not I needed to replace these. I'm 1500 miles without a light or code and approximately $225 poorer, but apart from the spilled blood and bruised ego, I'm feeling good about the truck...

I think that O2 replacement ease may be dependent upon the individual truck (and the Owner's ingenuity/tenacity). Good luck. As I firmly believe, ongoing preventive maintenance such as this is the key to keeping your Rover operable over the long haul.

DRW

 

The easy way to do the O2 Sensors is to cut the wires, drop the Y-pipe, remove the connectors, Connect new O2 Sensors to pigtails, install y-pipe, bolt on O2 Sensors. With the y-pipe removed it sure is easy busting those O2 sensors free.

The only reason I did it this way was because I was replacing the y-pipe due to the pipe busting at the weld on the passenger side flange. But no busted knuckles, no blood, and minor swearing.

 

I don't even know what "dropping the y pipe" means, but if it is easier than my story, you're my new hero...

 

The y-pipe is the exhaust pipe that runs from the exhaust manifolds and has the two catalytic converters on it. The pipe that holds the O2 sensors.