Ok something has to be wrong, MPG dropped massively!

[joe_peters]

I have NTK on my 98 4.0L (upstream) and no issues. I still need to replace the downstream, along with the cat I have in the garage.

Thanks for the tip on checking pulley resistance by hand with the belt off. Don't know why, but I never would of thought of that.

Isn't there a way to check O2 sensors using an analog multimeter? I've never tried it, but remember something about this.

It would be better to borrow/rent/find a friend with a scanner that directly reads real time data so you can see what the "upstream" o2 sensors are doing.

 

[inv3ctiv3]

I don't understand why there are SO many bosch ones, like 6 different upstream ones:

http://www.partsgeek.com/catalog/2001/jeep/cherokee/fuel_injection/oxygen_sensor.html

 

[joe_peters]

I don't understand why there are SO many bosch ones, like 6 different upstream ones:

http://www.partsgeek.com/catalog/2001/jeep/cherokee/fuel_injection/oxygen_sensor.html

There are "direct fit" or "universal" o2 sensors--"direct fit" means plugs right in, "universal" means you will almost always have to cut, solder, and heat shrink the harness.

Then, you have two "upstream" sensors, and they are NOT identical. Then there are two "downstream" sensors, and they are NOT identical.

So, you have two upstream, two downstream, and two style choices--about eight different sensors just from ONE manufacturer.

 

[inv3ctiv3]

There are "direct fit" or "universal" o2 sensors--"direct fit" means plugs right in, "universal" means you will almost always have to cut, solder, and heat shrink the harness.

Then, you have two "upstream" sensors, and they are NOT identical. Then there are two "downstream" sensors, and they are NOT identical.

So, you have two upstream, two downstream, and two style choices--about eight different sensors just from ONE manufacturer.

Yea I did a little more digging last night and found out these are the two I need:

http://www.amazon.com/Bosch-13122-O...TF8&colid=2Z07EBN7DPQSZ&coliid=I2JZCJ3ANBB6O0

http://www.amazon.com/Bosch-13100-O...UTF8&colid=2Z07EBN7DPQSZ&coliid=IZNRQQUFJINXM

I'm also doing a full cooling system update in which I will test the alternator and power steering pulleys and I've seen you post in a lot of those threads Joe Peters and wanted you opinion on what I'm getting:

CSF 3-row:

http://www.amazon.com/CSF-98-01-Jee...TF8&colid=2Z07EBN7DPQSZ&coliid=I3PDEBWCSDRTPO

Stant 195:

http://www.amazon.com/Stant-45359-S...TF8&colid=2Z07EBN7DPQSZ&coliid=I1EYPR38GPZ5NO

Goodyear belt (should I get a new idler pulley too?):

http://www.amazon.com/Goodyear-4060...TF8&colid=2Z07EBN7DPQSZ&coliid=I33LI18JX7PDCU

And I'm gonna go to Napa and get the following (unless you can recommend good brands I can find on amazon/online):

Water Pump - New (there are too many brands to choose from but saw you post Napa makes good ones)
Fan Clutch
Hoses
What else should I get to replace while I'm doing all this?


And I wanna tow my dirtbikes up to Mammoth Mountain so I wanna get this, seems like a good deal to me:

http://www.amazon.com/Flex-lite-411...TF8&colid=2Z07EBN7DPQSZ&coliid=I3PIVJAEORRKX5