With a 2.2-liter four-cylinder engine and a five-speed manual transmission you 1997 Camry was built to conform to either federal emissions or California emissions. If your vehicle is built to California emissions you will have a catalytic converter as part of the exhaust manifold and a second converter midstream in the exhaust piping. A clogged catalytic converter on your Camry will share the same tale tale signs as other vehicles experiencing the problem. The catalytic converter is very important to protect the environment and is required by law in most states to me emissions standards.
Your Camry is equipped with a three-way catalytic converter that reduces and breaks down several dangerous gases that are produced from the combustion process. The first pass through for the exhaust is through the reduction catalyst to reduce NO and NO2 gasses. The second pass is the oxidation catalyst that reduces unburned hydrocarbon and carbon monoxide. The third process in the catalyst process in the control system. The control system relates to the oxygen sensors mounted at both ends of the converter to detect and report to the computer the amount of oxygen left in the exhaust system.
The most common and well recognized sign of a clogged catalytic converter is a distinctive smell of sulfur or rotten eggs. A natural compound created from the fuel when burned in the combustion chamber is hydrogen sulfide. Hydrogen sulfide is normally broken down into sulfur dioxide as it passes through the catalyst in the converter, but when the converter materials are worn or damaged this doesn't happen. The Hydrogen sulfide then escapes past the converter and produces a rotten egg or sulfur smell. This is normally caused from the additional sulfur from unburned fuel being burned in the converter and is one of the last signs that appear as a result of a clogged or damaged converter. If your exhaust gas smells like rotten eggs, you will need to replace the converter and diagnose the cause of such a rich fuel mixture.
A catalytic converter is designed to allow exhaust to flow almost freely and provides very little restriction. As build up occurs inside the converter, there is more and more resistance to the exhaust flowing freely creating back pressure. The creation of back pressure makes the engine labor harder and will greatly reduce your engines performance. In your Camry this will be evident has a spurt or mild to heavy hesitation during moderate acceleration. In extreme cases the catalytic converter can prevent an engine from even running when clogged because there is no escape for any of the exhaust gases.
Oddly enough, even though the catalytic converter functions entirely inside its shell, there are visual signs that can be seen on the outside of the case. Support you Camry in the air with jack stands and visually inspect the converter case. A warped or heat colored case will tell you that the catalytic converter is getting very hot as a result for burning fuel and the converter working harder to pass the exhaust through it. This heat can be noticed when the vehicle has been driven or running for a reasonable amount of time because the converter will begin to glow red when it gets hot enough to damage or warp the case.
There are not a lot of ways to test for a clogged converter, but it can be done. You can drill a small hole in the exhaust before the catalytic converter to test the back pressure created from the catalytic converter. In general the back pressure from the catalytic converter at idle shouldn't exceed 1.25 psi at idle or 4 during snap acceleration. Anything above these readings indicate some blockage; the higher the back pressure the worse the blockage, respectively. You can also use an infrared temperature gauge to check the temperature before and after the catalytic converter. Extreme drops in temperature at the outlet of the converter as opposed to the inlet indicates the converter is clogged. Replacing the catalytic converter is as simple as removing the oxygen sensors and unbolting the converter from the exhaust manifold and rear muffler pipe. Replace the gaskets at both ends of the converter and tighten the mounting bolts in rotating sequence until tight to ensure the mating surfaces are flush and seal properly.
