Does a Catalytic converter effect idle and emissions?

In a vehicle's exhaust system, oxygen sensors play a crucial role in monitoring and adjusting the air-fuel mixture to ensure optimal engine performance and minimize emissions. The 2006 Trailblazer, like many modern vehicles, typically has two oxygen sensors: one located before the catalytic converter (referred to as the upstream sensor) and one after the catalytic converter (referred to as the downstream sensor).
The upstream oxygen sensor monitors the oxygen content in the exhaust gases before they enter the catalytic converter. This information is used by the engine control unit (ECU) to adjust the fuel injection and air intake to achieve the ideal air-fuel ratio for efficient combustion. Failure to replace a faulty upstream oxygen sensor can lead to decreased fuel efficiency, increased emissions, and potential engine performance issues.
The downstream oxygen sensor, located after the catalytic converter, serves a different purpose. Its primary function is to monitor the efficiency of the catalytic converter by measuring the oxygen levels in the exhaust gases after they have passed through the converter. The ECU uses this information to ensure that the catalytic converter is effectively reducing harmful emissions such as carbon monoxide (CO), hydrocarbons (HC), and nitrogen oxides (NOx).
While a malfunctioning downstream oxygen sensor may not immediately affect engine performance or fuel efficiency, it is still important to replace it if faulty. A failing downstream sensor can lead to increased emissions and may cause the vehicle to fail emissions tests. Additionally, it can result in damage to the catalytic converter over time, leading to costly repairs.
In summary, while the upstream oxygen sensor is more critical for immediate engine performance and efficiency, the downstream sensor plays a crucial role in monitoring and maintaining the effectiveness of the catalytic converter and ensuring compliance with emissions regulations. Therefore, it is important to replace both oxygen sensors as recommended to ensure proper vehicle operation and minimize environmental impact.

Do you have a performance problem or an emission problem? Who is telling you your cats are bad and need to be replaced? Of course the average converter lasts about 10 years so yours could be not as effective now as they were new. Any good muffler shop can replace them.

catalytic converter .
In order to control emissions, a catalytic converter converts any harmful exhaust emissions into harmless water vapor and carbon dioxide.
The powertrain control module (PCM) has the capability to monitor this process by using a rear-heated oxygen sensor (HO2S 2). The HO2S 2 , located in the exhaust stream past the catalytic converter, produces an output signal which indicates the storage capacity of the catalyst. This in turn indicates the catalysts ability to convert the exhaust emissions effectively. If the catalyst is functioning properly, the HO2S 2 signal will be far less active than the signal produced by the front oxygen sensor (O2S 1).

Mainly increased emissions and a failure at the smog test. There isn't much effect on drivability.
.

SECTION 309-00: Exhaust System 2003 Focus Workshop Manual DESCRIPTION AND OPERATION Procedure revision date: 01/24/2003 Exhaust System Printable View (214 KB) Vehicles with 2.0L Zetec-E engine
Item Part Number Description 1 - Bracket 2 - Gasket 3 - Catalytic converter 4 - Bracket 5 - Gasket 6 - Front muffler 7 - Rear muffler 8 - Hanger 9 - Flexible pipe

Vehicles with 2.0L SPI engine
Item Part Number Description 1 - Gasket 2 - Catalytic converter 3 - Bracket 4 - Gasket 5 - Front muffler 6 - Rear muffler 7 - Hanger 8 - Bracket 9 - Flexible pipe

Vehicles with 2.3L PZEV Engine
Item Part Number Description 1 5G232 Catalytic converter 2 5K222 Mounting bracket 3 5K282 Head shield 4 9451 Gasket 5 5A262 Insulator 6 5E292 Converter and muffler assembly 7 9448 Gasket 8 5G203 Flex Pipe NOTE: The exhaust systems shown in this section are production systems.
The exhaust systems are of a two-piece construction for production and five-piece construction for service.
Catalytic Converter
The catalytic converter fitted to the Focus range resembles a small muffler. Because of the high temperatures at which the catalytic converter operates, the vehicle body areas around the catalytic converter are protected by heat shields. The catalytic converter controls three emissions; Hydro carbons (HC), carbon monoxide (CO) and oxides of nitrogen (NOx).
Catalyst deactivation due to poisoning
Sulphur (S) in the fuel can cause deactivation of the catalyst.
Lead (Pb) in fuel can cause a severe deactivation at levels above 5 mg per liter of fuel. It is therefore essential that vehicles with catalytic converters always operate on unleaded fuel.
Zinc (Zn) and phosphorus (P) present in some oils, can cause deactivation if oil consumption is high.
The effect of sulphur is felt most if it is released from the catalytic converter as hydrogen sulphide (H2S). This has an unpleasant odor similar to rotten eggs. Changing the fuel manufacturer may help in reducing this phenomena.
To minimize H2S emissions, it is essential that the idle CO level is within specification and that the engine emission system is functioning correctly. For additional information, refer to Section 303-08A or Section 303-08B.
CAUTION: If temperatures exceeding 900°C are achieved the catalyst substrates will start to deteriorate. It is important that the cause is defined and rectified if subsequent melts are to be prevented.
Catalyst melts are normally accompanied by loss of power due to excessive back pressure. For additional information, refer to Section 303-07A or Section 303-07B.
High substrate temperatures are caused by the ignition or the fuel systems. For additional information, refer to Section 303-07A or Section 303-07B.
Misfires at high engine speed may result in an almost instantaneous melt.

Your catalytic converter is not doing it's job efficiently enough and it is setting off your sensor. This problem is emissions problem and usually has no effect on the operation of your vehicle( unless the converter clogs) As long as you don't live somewhere they do emissions test you don't really have to worry about it. However if you want to fix it you can take converter off and run a straight pipe or to do it "right" you could go pay way to much to get a new converter put on.

the O2 sensor works on one volt .5 is around the running voltage, i would refit the air hose as it will run the converter hotter at idle.

Did you install new spark plugs? Definitely replace the O2 sensor.

There are two ways a converter can fail:

• It can become clogged.
• It can become poisoned.

There really is no "inspection port" for the consumer or mechanic to see an actual clog in a converter. Often, the only way to tell if a catalytic converter is malfunctioning (plugged) is to remove it and check the change in engine performance. When a clogged converter is suspected, some mechanics temporarily remove the O2 sensor from the exhaust pipe ahead of the catalytic converter and look for a change in performance.
A catalytic converter relies on receiving the proper mix of exhaust gases at the proper temperature. Any additives or malfunctions that cause the mixture or the temperature of the exhaust gases to change reduce the effectiveness and life of the catalytic converter. Leaded gasoline and the over-use of certain fuel additives can shorten the life of a catalytic converter.
A catalytic converter can also fail because of:

• Bad exhaust valves on the engine
• Fouled plugs causing unburned fuel to overheat the converter

­Sometimes you can tell that a converter is clogged because you don't go any faster when you push the gas pedal. Also, there usually is a noticeable drop in gas mileage associated with a clogged catalytic converter. A partially clogged converter often acts like an engine governor, limiting the actual RPMs to a fast idle. A totally clogged converter causes the engine to quit after a few minutes because of all the increased exhaust back pressure.
The catalytic converter, like the rest of the emissions system, typically has a warranty length that exceeds the term of the warranty for the rest of a typical U.S. automobile.
Here is a safety reminder: Do not park your car over tall grass or piles of dry leaves. Your car's perfectly running catalytic converter gets very hot -- enough to start fires! You can keep it running well by keeping the ignition system in top shape, to prevent any unburnt fuel from entering the catalytic converter.

I'd say most likely you're catalytic converter and or the EGR valve may need repaired or fixed. THe EGR recycles some exhaust in order to recombust fuel. The catalytic converter reduces toxicity of emissions. Car dealers can diagnose these thing for around $100-200.