Your Mercury Grand Marquis leaves the factory with a catalytic converter. It can run into problems over the normal life of the vehicle, and is often accompanied by OBDII code P0420. Below we’ll cover the location, price, and symptoms of a bad torque converter in your Grand Marquis.
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Grand Marquis Catalytic Converter Location
Mercury Grand Marquis Bad Catalytic Converter Symptoms
What is a Catalytic Converter Anyway?
The catalytic converter, which is often mispronounced and spelled “cadillac converter”, is the most important part of your Grand Marquiss emissions system. It takes the emissions gases that are a bi product of the normal combustion process and reduces them down to levels that meet federal emissions regulations.
The catalytic converter uses a catalyst to burn off residual fuel vapor and turn it them into:
- Water
- Carbon dioxide
- Heat, lots of heat
Catalytic converter’s have been common in all domestic automobiles for nearly 40 years. They have gotten better at what they do from an exhaust flow perspective, and an exhaust cleansing perspective.
Where is the Grand Marquis’s Catalytic Converter Located?
The exact location of the catalytic converter is going to depend on the model year and engine size of your Mercury Grand Marquis. But, they are not that difficult to locate. The catalytic converter itself is a part of the exhaust system. Tracing it, you’ll find it somewhere between the tail pipe and intake manifolds.
They almost always have a heat shield around them and an oxygen sensor somewhere before them. It is necessary for the catalytic converter to be before the muffler. The muffler is really the only thing that you can confuse for the catalytic converter on your Mercury Grand Marquis.
The catalytic converter may be bolted or welded on depending on the year and make of the vehicle.
Catalytic Converter Price: Mercury Grand Marquis
The catalytic converter for your Grand Marquiss cost will vary by model year and engine size. But, as a rule catalytic converters are not cheap. They are one of the most stolen items on a vehicle there is. They are almost always more than $100, and can cost several hundred dollars for a large on that sits behind a V8.
Since it often requires welding to replace the catalytic converter, it’ll often mean a trip to the exhaust shop. Later model vehicles can cost over $1000, when it’s all said and done.
Catalytic converters also have a have a scrap value of up to $250, with the average being closer to $90. Here’s the source on that, if you’d like to check the going rates in the scrap market.
Mercury Grand Marquis: Bad Catalytic Converter Symptoms
It is not uncommon for the catalytic converter to fail, as the years and mileage take their toll. They will fail faster if there is an issue with misfiring or a bad air/fuel mixture.
When your Grand Marquis has a major engine problem, the check engine light will begin flashing. In most cases, this flashing condition occurs to help try and save the catalytic converter.
Most of the symptoms of a bad catalytic converter have to do with the lack of exhaust flow through the Cat. Once it gets so clogged, your Grand Marquis will be barely drivable.
Here are the most common signs of a bad catalytic converter in a Mercury Grand Marquis:
- MPG Suffers– As the exhaust flow begins to slow, your gas mileage will as well.
- Service Engine Soon Light– Any vehicle made in the last 20 years is going to have an onboard OBDII computer. It’ll give you the “trouble code” that you’d need to diagnose and repair your Grand Marquis’s emissions system.
- Failure to Start– Once the catalytic converter is so clogged, there won’t be enough air flow for your Grand Marquis to start.
- Darker Exhaust Smoke
- Rotten Egg Smell
- No Throttle Response at Speed– If your Grand Marquis feels like it just won’t go any faster than a certain speed without feeling like it is out of power, that’s a very typical sign that a catalytic converter is failing.
Here’s a pretty good video from Scotty Kilmer on this subject:
Conclusion
If you are having problems with your Grand Marquis’s catalytic converter, it is often accompanied by P0420. It can be an expensive repair. If you feel like there is anything that you can add to the discussion, please leave a comment below. Good luck fixing your issue!