Pre cat O2 sensor question

Boz_10 · 07-15-08, 11:28 PM

Finally got my catalytic converter installed after someone cut it out. I had a friend install/weld some exhaust piping along with Magnaflow single cat 2.5" in place where the thieves cut the stock one out.
The post cat O2 sensor is in place, but the pre cat O2 sensor is missing. My friend did not know there is a pre cat O2 sensor so he did not make a hole for pre cat O2 to be installed in. Basically, now I only have post cat O2 sensor.

My question is, in my case ('97 FZJ80 w/~ 155K miles), of what importance is the pre cat O2 sensor? Is it all right to drive without one? How hard would it be to drill a hole to place a pre cat O2 sensor in?

I can reset the ECU, but am I doing more harm by not having the correct oxygen/fuel mixture by not having the pre cat O2 sensor? Is my timing, power, or mpg compromised?

Any advice is helpful!!

Thanks

PS: I searched, but got limited results back.

Firedog · 07-15-08, 11:42 PM

I don't know about what damage it could do, but i would imagine that it will effect the mileage, power and possibly the longivity of your new cat.
It's easy enough to replace the bung, just order one from Slee, cut a hole for it and weld it in place (or any muffler shop should be able to do it for you.)

Beowulf · 07-15-08, 11:49 PM

Quote:

Originally Posted by Boz_10

My question is, in my case ('97 FZJ80 w/~ 155K miles), of what importance is the pre cat O2 sensor? Is it all right to drive without one? How hard would it be to drill a hole to place a pre cat O2 sensor in?

Your truck is OBD-II and both O2 sensors are important. Very important. You will be in a limp-home mode without the O2 sensor so your truck is not running optimal. The timing is retarded, the fuel mapping reverts to a base map. Your power will be down. Your MIL will stay on. You'll never pass emissions.

You should follow firedog's advice and install a bung and O2 sensor.

-B-

Boz_10 · 07-16-08, 12:30 AM

...thanks for the quick reply!!

Sorry for the ignorance, but what is a "bung"?

Beowulf · 07-16-08, 12:36 AM

From the Slee web site:

http://sleeoffroad.com/products/prod...driveshaft.htm

-B-

nicholas · 07-16-08, 03:06 PM

I agree, go with the slee bung and an OEM sensor from CDan. Mine had a generic O2 sensor in the front that was worthless. I got horrible gas mileage and I probably added a lot of carbon deposits in my engine as well as possibly shortened my cat's life.

07-15-08, 11:28 PM	#1
Boz_10 IH8MUD Rookie Join Date: Oct 2006 Posts: 26	Pre cat O2 sensor question Finally got my catalytic converter installed after someone cut it out. I had a friend install/weld some exhaust piping along with Magnaflow single cat 2.5" in place where the thieves cut the stock one out. The post cat O2 sensor is in place, but the pre cat O2 sensor is missing. My friend did not know there is a pre cat O2 sensor so he did not make a hole for pre cat O2 to be installed in. Basically, now I only have post cat O2 sensor. My question is, in my case ('97 FZJ80 w/~ 155K miles), of what importance is the pre cat O2 sensor? Is it all right to drive without one? How hard would it be to drill a hole to place a pre cat O2 sensor in? I can reset the ECU, but am I doing more harm by not having the correct oxygen/fuel mixture by not having the pre cat O2 sensor? Is my timing, power, or mpg compromised? Any advice is helpful!! Thanks PS: I searched, but got limited results back. __________________ 1997 FZJ80, Locked, almost stock -seldom driven. 1999 Maxima SE 5speed, MM EVO5 18", H&R+ KYB AGX 2.5" drop - DD Last edited by Boz_10; 07-16-08 at 12:28 AM.

07-15-08, 11:42 PM	#2
Firedog IH8MUD Regular Join Date: Jul 2007 Location: Southwest Virginia Posts: 321	I don't know about what damage it could do, but i would imagine that it will effect the mileage, power and possibly the longivity of your new cat. It's easy enough to replace the bung, just order one from Slee, cut a hole for it and weld it in place (or any muffler shop should be able to do it for you.) __________________ Keith '77 FJ-40 OME, ARB, SM465, Family cage, 33" Swampers, and lots of rust. '93 FZJ-80 - Flare-less, Factory Lockers, ARB, OME "J" Lift, IPOR Skid Plate, Toyo 315 MT's, Sliders, Side Protection, and Rear Bumper by M&M Fab (http://mandmfab.com/id55.html)...... This is just the begining... '02 Chevy 2500 Duramax to tow the toys http://www.4x4bcds.com/ '92 Toyota Celica GT Convertible - The newest Toy, 113,000 miles and unmolested!

07-16-08, 12:30 AM	#4
Boz_10 IH8MUD Rookie Join Date: Oct 2006 Posts: 26	...thanks for the quick reply!! Sorry for the ignorance, but what is a "bung"? __________________ 1997 FZJ80, Locked, almost stock -seldom driven. 1999 Maxima SE 5speed, MM EVO5 18", H&R+ KYB AGX 2.5" drop - DD

07-16-08, 12:36 AM	#5
Beowulf The quick brown fox ..... Join Date: Mar 2003 Location: Somewhere in the foothills... Posts: 10,566	From the Slee web site: http://sleeoffroad.com/products/prod...driveshaft.htm -B- __________________ 97 FZJ80 - Wing Nut MAF, locked, 315 Toyos, 4.88s, Slee 4", George's sliders, Slee bumpers, M12000, OBA, Outback drawers + other stuff. Transformation in progress... Sometimes you find yourself in the middle of nowhere. And sometimes in the middle of nowhere, you find yourself.

07-16-08, 03:06 PM	#6
nicholas IH8MUD Addict Join Date: Jun 2006 Location: IA Posts: 892	I agree, go with the slee bung and an OEM sensor from CDan. Mine had a generic O2 sensor in the front that was worthless. I got horrible gas mileage and I probably added a lot of carbon deposits in my engine as well as possibly shortened my cat's life. __________________ 97LX450, 141K, 285CooperSST's, OME851/860's, S/C, CDL 7-Pin, Landtank MAF, Slee SS lines, 100 pads, silicone PHH, Raventai temp, CDan parts throughout($5K+). Chillin' in Cornfeilds (IA) studying.

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