Alright folks I decided not to feed Mitsubishi and do my own O2 swap. Quote from Mitsi = $370 parts and labour.
Cost of sensor $130 + 45 minutes elbow grease.

You will need:
Around 45 minutes - 1 hour
O2 sensor (courtesy of Anthony @ Phillcom Rally)
22mm ring spanner
Small mallet (or shifter for whacking things)
WD40/RP7/Penetrene
1 x Preacher Man special tool (2m of strong string )

1. Ring Anthony and get a really good price on O2 sensors
2. Collect O2 sensor from Anthony
3. Read Haynes manual and get a low down of how this thing works
4. Be really sure that you need to replace your O2 sensor
5. Start engine and run for 15 minutes. This will help the metal of the exhaust expand making O2 sensor removal easier
Disconnect Negative battery terminal (after turning off the engine)
6. Raise vehicle front end, chock rear wheels and secure front end on axel stands or ramps
7. Get in to the passenger foot well, pull back the carpet (need to remove scuff plate & plastic cover thingemy from under the glove box)
8. Undo the 3 screws holding in the metal kick plate at the deep right hand side of the foot well
9. Look for a white connector with 4 wires (Black, grey, white & white). Disconnect and tie a 2m piece of string around the plug (male end). This will help you to pull the O2 sensor cable back in to the cabin
10. Get under the car and locate the O2 sensor. It's in a metal flange type thing near the Cat, look for the cable that goes in to the bottom of the car.
11. Spray O2 sensor with WD40 and allow to soak in
12. Get your 22mm spanner and start to apply elbow grease (involves grunting & use of profanities)
13. Belt the spanner a few times if necessary. Keep on tapping till it's loose.
14. Grunt and use profanities again if necessary.
15. Grunt and profanitise again when the sensor finally breaks free and you skin your knuckles.
16. Unscrew all the way, then clean the thread hole with a wire brush
17. Pull the sensor free from the car by pulling the rubber gromet free from the floor pan and carefully pull the O2 sensor connector away. Notice how ingeneous the Preacher Man special tool is!
18. Tie the string to the connector of the new sensor and locate in the floor pan access tunnel.
19. insert the new O2 sensor in to the exhaust pipe. Tighten with a spanner until tight (about a half turn past tightish)
20. Get out from under the car, pull on the Preacher Man special tool (string) and notice how easily the connector comes in to the cabin.
21. Reconnect the clips, replace carpet
22. Reconnect the battery terminal.
23. Lower the car and rejoice in a job well done!

Word of warning: if you have an enclosed garage, do not run the car with the the O2 sensor disconnected! All sorts of nasty fumes are emitted. Even in my open and airy car port, 15 minutes of running was enough to make me near vomit!

Enjoy fellas and femallas.

Job well done!!

someone told me that this sensor could be the reason my car does not start sometimes and other times it will run perfect...even mitsubishi had a look and couldnt work it out.
What do you reckon?

Nice one. Someone make this thread sticky.

someone told me that this sensor could be the reason my car does not start sometimes and other times it will run perfect...even mitsubishi had a look and couldnt work it out.
What do you reckon?
It's possible, although I don't think the sensor actually kicks in until it's warm?? Anything is possible, these beasts are real enigmas.
I just knew that my car was running really rich and I had shocking efficiency.

someone told me that this sensor could be the reason my car does not start sometimes and other times it will run perfect...even mitsubishi had a look and couldnt work it out.
What do you reckon?

Could also be a dirty/contaminated MAF ... when was the last time you replaced your air-filter?

It's possible, although I don't think the sensor actually kicks in until it's warm?? Anything is possible, these beasts are real enigmas.
I just knew that my car was running really rich and I had shocking efficiency.
The oxygen sensor is just feedback for the engine computer, which constantly adjusts the tuning of your engine depending on how much oxygen there is remaining in your exhaust.

Computer will try to lean it out as much as possible - better economy, less pollution. If the sensor is broken/missing/disconnected, the computer will just run at a fallback setting... usually pretty rich.

If you've been driving around with a dead O2 for a while, your cylinders & plugs could get sooted up from all that excess carbon. Probably bad for the cat too (both feline & 'zorst :P ).

Think Bosch is world's biggest maker of O2s and its a pretty generic part.


If anyone's having trouble with cold starting, have your fuel injectors checked & cleaned. They also have a "cold start" setting that should be checked by a pro.