Bought my Mark VIII last week and the owner said the car needs O2 sensors. He said that was diagnosed by his mechanic but he didn't have the money to spare. The check engine light comes on intermittently and the car smells like rotten eggs (well, sorta). Oh yeah, it idles a bit rough also. Would the 02 sensors cause these symptoms?. Anyway I'm buying new sensors tomorrow and want to know if they are located in an accessible location and if its a easy or tough job. I've done plenty in the past on other cars and they went easy but have not even looked to see where they are on this one yet. Thanks for the help.
02 Sensors
- Thread starter Destroyer
- Start date
You didn't say what year Mark....At any rate, they are more or less accessible. Maybe you'll need to drop the right hand tube from the manifold to remove the right one and the left one's connector may need to be inserted using a small hand and a few USMC magic words.
They are located on the top of the forward cats.
They are located on the top of the forward cats.
Yay For Jesse 
Yay For Jesse
LOL......I'm coming to the rescue here dude!(slowly but surely I'll get all my posts back!)
Hey guys, just wanted to post some pics to help anyone hoping to change their 02 sensors soon, it was pretty easy because I had the ease of having a lift. Also, don't overtighten the sensors when you install them because if you have to do it again you'll hate yourself.
Here is what I used to loosen them......
Flex Handle Ratchet and a 7/8" Crows Foot (or one that fits your O2)
For the Drivers side, basically put the Crows Foot on the ratchet as you see in above picture and "lay" the ratched on top of the catalytic converter and you will only get maybe 1/4 of a turn on the O2, move the crows foot and turn it again. It should now be loose enough to unplug and twist out by hand.
Now the passanger side is a little different, put an extention on the ratchet and you'll barely be able to get the Crows Foot on, but you should be able to loosen it. If not try turning over the Crows Foot. Make sure you unplug the O2 or it will be harder to get out because the wires will twist.
This pic is showing how I reached up over the passengerside "cat" to unscrew the O2.
Hope this helps someone. The car was "racked" and "un-racked" in less than 30 minutes.
Yay For Jesse
LOL......I'm coming to the rescue here dude!(slowly but surely I'll get all my posts back!)
Hey guys, just wanted to post some pics to help anyone hoping to change their 02 sensors soon, it was pretty easy because I had the ease of having a lift. Also, don't overtighten the sensors when you install them because if you have to do it again you'll hate yourself.
Here is what I used to loosen them......
Flex Handle Ratchet and a 7/8" Crows Foot (or one that fits your O2)
For the Drivers side, basically put the Crows Foot on the ratchet as you see in above picture and "lay" the ratched on top of the catalytic converter and you will only get maybe 1/4 of a turn on the O2, move the crows foot and turn it again. It should now be loose enough to unplug and twist out by hand.
Now the passanger side is a little different, put an extention on the ratchet and you'll barely be able to get the Crows Foot on, but you should be able to loosen it. If not try turning over the Crows Foot. Make sure you unplug the O2 or it will be harder to get out because the wires will twist.
This pic is showing how I reached up over the passengerside "cat" to unscrew the O2.
Hope this helps someone. The car was "racked" and "un-racked" in less than 30 minutes.
Does that really matter? Lol....they all have the same exhaust(in relation to the position of the sensors)
97-98 Just have two more sensors towards the rear
I hope so, all the more reason to ditch them. Ok, since I just brought up the subject of dichin the cats, what effect would it have?. No "check engine" light or anything right?. I'm thinking I can ditch the cats, put on some true dual exhaust w/flowmaster or magnaflow mufflers and call it a day.
No CEL. The motor will breathe better. But you do risk failing emissions if you have emission nazis in your state/county. I'm sure a High flow cat can take care of that though. And the car will be louder. Some like this, some don't. You might even get a little better mileage out of it.
Wrong. The rotten egg smell is the sign of a PROPERLY working "cat". If the cat has failed, you wouldn't smell anything but a strong hint of RAW fuel.
The reason he got the rotten egg smell is because the O2's were failing, causing the car to run rich, in turn overworking the cats causing them to burn off all that excess raw fuel....walla rotten eggs with a check engine light.
Destroyer......unless you get headers, you're NOT going to be able to remove the drivers side cat. You can bash the substrate out of the inside of it, but you risk pieces shooting up into the engine. I'd recommend removing the resonator and the 3rd cat and running true duals(NOT flowmasters!). This is what the drivers side exhaust manifold looks like......this is from my exhaust post. http://mark8.org/vbulletin/showthread.php?t=15018
Last edited:
Mad1stGen
Registered
Here's C&P from corral ad:
"Set of 4 sensors for 4.6 engines, 2 and 4 valve models. These O2's will fit ANY 4 wire application, V8-V6 ect. $75 a set SHIPPED BY MAIL ONLY. Delivery can take up to two weeks, but it does not usually take that long. The sensors are new unused and have antiseize grease on the threads. PAYPAL ACCOUNT IS 78pinto@sympatico.ca The plug end MAY require some simple modification to fit in your O2 loom end, it is easy to do with a sharp knife, simply trim off the guide tabs on the end of the O2 plug end. They will work on ANY 4.6 car. For a set of front O2's only, they are $55 for the set of two, shipped. At a dealership or parts place these cost about $70 to $80 apiece.... this is a great deal!"
The guy is legit, I bought several sets of these from him. You can substitute front for back sensors and get 4 for $75 as well. You can't beat $17.50 shipped for OEM sensors I don't care how good your internet kung-fu is.
"Set of 4 sensors for 4.6 engines, 2 and 4 valve models. These O2's will fit ANY 4 wire application, V8-V6 ect. $75 a set SHIPPED BY MAIL ONLY. Delivery can take up to two weeks, but it does not usually take that long. The sensors are new unused and have antiseize grease on the threads. PAYPAL ACCOUNT IS 78pinto@sympatico.ca The plug end MAY require some simple modification to fit in your O2 loom end, it is easy to do with a sharp knife, simply trim off the guide tabs on the end of the O2 plug end. They will work on ANY 4.6 car. For a set of front O2's only, they are $55 for the set of two, shipped. At a dealership or parts place these cost about $70 to $80 apiece.... this is a great deal!"
The guy is legit, I bought several sets of these from him. You can substitute front for back sensors and get 4 for $75 as well. You can't beat $17.50 shipped for OEM sensors I don't care how good your internet kung-fu is.