Repair Topics / Catalytic Converter-1 / Catalytic Converter-2

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Catalytic Converter Questions and Answers - This category contains featured questions as examples. They relate to most vehicles.

Question: 2004 Nissan Sentra 1.8_mileage: 41,000. I just bought a low mileage Nissan Sentra. The fuel economy is terrible, not what I would expect from a V6. It sometimes hesitates to start. It warms up very fast but the interior gets unusually warm as though the catalytic converter is working overtime. The excess heat comes up through the floor. What is the likely cause and solution to this problem?

Answer: Scan computer for fault codes. You will probably find one indicating that your engine is running too rich which causes the catalytic converter to overheat. Check the fuel pressure regulator and check for faulty fuel injectors.

Question:  2002 Toyota Camry Mileage 80,000: When I drive at speeds 67+ mph, there is a really bad smell that comes from my car.  My ex, who is a mechanic, said it was the catalytic converter, but said it wasn't a problem, and that it's expensive to replace etc.  I like to drive fast, so I always smell that odor (like rotten eggs and burnt rubber), so I was wondering what I could do to fix this?  If I have to replace the converter, how much should it cost?  Or if there is something else that could be contributing to this smell that my ex overlooked?  Any insight would be appreciated.

Answer: The “rotten egg smell” that you mentioned is usually caused by fuel mixture in the engine that is too rich.  The catalytic converter may be faulty but before you replace it the “too rich” fuel mixture needs to be corrected.  As far as the cost...check around in your area at different muffler shops and compare prices.

Question: 2002 Lexus 300c mileage: 110,000. Just wanted to ask you if a catalytic converter overheats to the point where it is so hot it is igniting the bottom undercoat of a car along with a slight oil leak, just to make the point the converter is really red hot, anyway, isn't there a possibility that the converter becomes damaged? Besides testing the emissions to see, if they are within parameters is there any other form of diagnostics on catalytic converters. My problem is that the car bottom caught on fire as a result to the converter overheating. No doubt the oil leak has to be fixed, as well as any problem the car was having to make the converter overheat, but what about the converter itself? A converter for my car runs approximately nine hindered dollars. How can I really know if my car needs to have one replaced or has been damaged and will need replacement soon?

Answer: It is difficult to say if your catalytic converter is okay from here. The converters are made to run hot but if they are severely overheated, they can be damaged. We suspect the cause of the converter overheating would be in the emission control system, possibly an air control valve that is not functioning properly. Another possibility would be a leaky fuel injector or a faulty fuel pressure regulator that would cause the engine to run rich.

To test for a plugged converter, drill a small hole in the exhaust pipe right before the catalytic converter. Install a temporary hose fitting and attach a long rubber hose and a 0 to 10 pound pressure gauge. With the gauge inside the car, drive up a hill or accelerate and read the pressure. Normal is 2 to 3 pounds, restricted 4 pounds or higher.

Question: 2002 Tahoe Z71 mileage: 58,260 km. I have had the Tahoe for about 4 months now. Everything has been fine up until a trip to the lake towing our trailer. About an hour into the drive, a smell came into the cab of the truck. (A mix of propane and rotten eggs) It was actually quite strong and persisted for the rest of the drive (1 hour). Since that day the smell comes and goes. Sometimes when the truck is cold and sometimes after it has warmed up. I just had it to the service guys to check it out. They said it may be the catalytic converter but everything checked out OK. They said that they smelled a "faint" odor and it didn't last.

Answer: The smell is probably from the catalytic converter. When you were towing the trailer, you required more power from your engine and consequently, more fuel through the converter. We can only guess that the trailer disturbed the airflow from the back of the truck, which allowed some exhaust to invade the cab of your truck. The catalytic converter may have been overheated with the extra weight of the trailer thereby causing it to work at less than 100 percent efficiency now.

Question: 1997 Chevy Corvette mileage: 67,000. I got a code 34 on my computer, went in had another MAF put in, car ran fine for 3 days with no codes. Suddenly code 34 is back...what could cause this.

Answer: If the converter is partially plugged, it backs up the exhaust, which affects intake manifold vacuum. The airflow into the engine is then affected resulting in your code 34.

Question: 1999 Chevy 1500 mileage: 128,000.  I had some problems with my muffler.  It was 2 out, 2 cats, in to one muffler, one output.  I was told flow master was a very good muffler, and I would get better response.   So I got two, 2 chambers, and it felt like I lost some power, but had better throttle response.  Twenty thousand miles later I was told my cats were out, and I could hollow them out until I got the money for new ones, so I did.  Now I have even better response but less power.   Please help R.R.

Answer: Yes, your engine does require backpressure in the exhaust system to run properly.  The entire engine system and the exhaust are all engineered and tuned together for maximum performance.  Changing the mufflers to lower the backpressure affects the optimum performance of the flow in and out of the intake and exhaust valves.  In doing so, you have altered the balance that was designed for your car.  We would recommend returning to the original equipment.

Question:   1998 Nissan Pathfinder mileage: 110,000.   My Nissan Pathfinder stalled a few weeks back.  (It’s a 306E something engine, overhead, fuel injected.)  Then we noticed a few days later that the catalytic converter was growing extremely hot.   When removed it looked rotten inside.  We replaced it.  The new converter is not becoming red hot!  There is a clunking sound in the engine.  It barely runs.  In the past, there was a problem with a canister under the hood that effects the fuel mixture.  What's eating up my catalytic converter?

Answer: A catalytic converter will get over heated if the engine is running too rich.  Check the fuel pressure.  Also, check the fuel injectors to see if they are leaking and scan the computer for fault codes.

Answer:   Your problem sounds like too much fuel is being put into the engine from the fuel injectors.  Have the fuel injectors replaced.

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Repair Topics / Catalytic Converter-1 / Catalytic Converter-2