CEL, Catalytic and O2 sensors??

[Mark VIII]

I have a 1997 with 170,000 miles on it. It still has the original catalytic and original O2 sensors.

I'm getting a CEL and per my garage it is a bad Cat.

This may be a dumb question, but can a bad 2nd oxygen sensor (after the cat) cause this error code? I'm not sure how the car knows the cat is bad?

If I do need a cat and since I have a 1997, do i have to get the BMW cat from bavarianauto.com for $360, or can I use a universal cat?

It looks like worst case, I need to buy a $360 cat, 2-$100 to $150 oxygen sensors + install. This is going to be at least $700 .

I'm hoping just changing the 2nd oxygen sensor might fix this??

I live in a state with emissions inspection, so I do eventually have to fix this.

Ken

[jonchino]

You can pull out your O2 sensors and test them! Seach online how to test you o2 sensors.

I dont understand why most people use the factory cat for replacement? I live in Massachusetts and there are tons of exhaust shops. I got flowmaster muffler and a dual exhaust in my chevy for $300 installed.

When I put my engine back together I am going to get a aftermarket highflow cat w/ muffler(dunno, see what the guy says at the shop). In a few months I telll you what it was(unless i get a quote before that).


anyone have aftermarket highflow cat??

[L84THSKY]

That was my point exactly!

About to install the rear O2 sensor today. I know there is a special tool, but would a wrench or crescent wrench do the trick?
Any additional suggestions?

Just read this on Pelican's website:

Some of the symptoms of a failed oxygen sensor system are:

* Irregular idle during warm-up
* Irregular idle with warm engine
* Engine will not accelerate and backfires
* Poor engine performance
* Fuel consumption is high
* Driving performance is weak
* CO concentration at idle is too high or too low
* Check Engine light is illuminated

Originally Posted by Mark VIII

This may be a dumb question, but can a bad 2nd oxygen sensor (after the cat) cause this error code? I'm not sure how the car knows the cat is bad?

I'm hoping just changing the 2nd oxygen sensor might fix this??

I live in a state with emissions inspection, so I do eventually have to fix this.

Ken

[ClubSport]

The car knows the cat is bad by comparing before and after O2 sensor readings to each other. This formula doesn't work however when one or the other sensors is bad. I have used the blowtorch method to test O2 sensors with some success.

[cev12]

Originally Posted by L84THSKY

That was my point exactly!

About to install the rear O2 sensor today. I know there is a special tool, but would a wrench or crescent wrench do the trick?
Any additional suggestions?

I recently replaced my O2 sensors on my 96 OBDII. I used a 17mm wrench to get them out and put the new ones in.
Hope that helps

[L84THSKY]

Pelican Parts website says that getting the O2 sensor out of a 318 is difficult. Not sure if that comment also applies to a 318ti. Did you have a hard time accessing the rear sensor? The picture on the website implies it's difficult.

Originally Posted by cev12

I recently replaced my O2 sensors on my 96 OBDII. I used a 17mm wrench to get them out and put the new ones in.
Hope that helps

[cev12]

That sensor in the picture looks like the upstream, if I'm not mistaken. the downstream sensor is a little harder to get to than the upstream, after you unplug the wires you have to pull them out of a plastic cover that runs all the way to the sensor. The main frustrations are lifting the car high enough to get to the sensors and wrenching them loose if you're from up north.
Hope this helps.