NOTE: This is meant only as a reference, work on your car at your own risk and follow local laws, regulations, and safety procedures. Information and photos provided by Franky's Custom Shop - Fort Wayne, IN.Visit Franky's Custom Shop Here
Replacing a catalytic converter on a 2001 Chevy Impala 3.8 or 3800 series II V6
Today the 2001 Chevrolet Impala was feeling pretty sluggish. The car would not rev above about 3,000rpm in park or when driving. We noticed the exhaust was extra hot and seemed to be quite restricted. This really could only be a few things. We needed to check to see if the catalytic converter was plugged or if we had a different problem. The first thing we did was remove the front O2 Sensor. This is the sensor in the exhaust that is between the engine and the catalytic converter. Temporarily removing this sensor will create a way for exhaust gases to escape in front of the converter if it is plugged. A quick start up of the engine and a couple revs with this sensor removed will tell you if a plugged cat is your problem. The car reved like new with the sensor removed, so we knew we had a partially plugged cat.
NOTE: Do not run the car for more than 30 seconds or so with the sensor removed, hot gases will be coming out the hole and can cause a fire. Removing the sensor is for a quick test only, DO NOT DRIVE THE CAR WITH THE SENSOR REMOVED.
Calling around to a few shops in town gave us price quotes from about $450-$650 to replace the converter. We obviously were not going to pay that kind of price for something we can do ourselves, and as we have the ability we decided to show how it was done.
I neglected to take pictures of the original converter on the car, the pictures of the new converter will show the same thing.
This is a pretty simple procedure to remove and replace a catalytic converter, it can save your hundreds of dollars. That being said, the biggest enemy of a car guy or girl is RUST. If you have rusty bolts, which you most likely will since these parts are under your car, be careful not to break them, or any of your body parts. This will likely set you back many hours and many dollars if you do.
First thing you will need to do is remove the second or Rearward O2 sensor. This is the sensor that sits in the U bend behind your converter unit. First unclip the connection (there is a small white plastic locking pin that you will have to pull from the clip to be able to release the connection) You will need a 7/8 inch wrench for to remove the O2 sensor itself. Be careful not to damage the sensor, they cost about $65 each!
Below are two photos. These are if you were under the car looking up toward the engine. You can see the two bolts, one on either side of the exhaust pipe. These bolts go through the flange on the front of the pipe and bolt the catalytic converter unit to the exhaust manifold. You will need to first remove these two bolts (or nuts).
Next you will move to the flange behind the catalytic converter, where you will also remove the two bolts. (Caution, these bolts are most likely super rusty and will break easily if you are not careful, soak with a good penetrating oil 5 min or so before you attempt to remove. Oh and wear eye protection!)
At this point the only thing holding the converter unit to the car is the two rubber bands that support the exhaust, while supporting the main unit, pry the bands away from the hooks and remove the converter. It should come out easily.
This photo shows the bands and bolts up close.
Now that you have your catalytic converter removed, you will need to clean off any gasket material from the rearward flange. This flange should be the only one needing cleaned. The front manifold flange should be metal, be sure you remove the old one and get a new one so you don't have leaky exhaust.
Here is a picture of the rearward flange showing the old gasket that needed cleaned off. You only need to clean it from the part your keeping, this picture of the old cat is for example of the left over gasket material only.
So now you have everything all cleaned up, you have your new converter and have matched it up next to the old one, noting it is the correct one, you have your new gaskets and are ready to install everything.
I think the best way to re-install the converter unit is to first hook the rearward bands into the hooks, but do not yet install the bolts in the rear. Now install the front gasket and bolt the front flange to the exhaust manifold. Do not tighten them down all the way yet. When you have the front bolts about half way in, it is time to get your rearward flange bolts and gasket in place. Tighten the rearward bolts about half way.
Now that all your bolts are started and your converter unit is hanging in place, go back and tighten the front bolts all the way down, then tighten the rear bolts. When all the bolts are tight its time to re-install your rearward 02 sensor and plug in the electrical connection. Be sure to check the new converter unit for stickers, plastic packing tape and other things that may be stuck to the outside, remove anything you find that will burn!
Your car should now be ready to run.
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