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Ford Explorer Community - Maintenance - Modifications - Performance Upgrades - Problem Solving - Off-Road - Street
Explorer Forum Covers the Explorer ST, Explorer Sport, Explorer Sport Trac, Lincoln Aviator, Mercury Mountaineer, Mazda Navajo, Ford Ranger, Mazda Pickups, and the Ford Aerostar
My catalytic converter is rattling, like something inside is damaged. If I need a new cat what could i get that would increase my performance? Would it be a good to get a cat back exhaust at the same time to save on labor? I was looking to get a borla system.
You will usually smell a rotten egg odor if your cat is bad. If you do replace it go with a high flo cat and cat back system. You might save a little on labor but it will take almost the same amount of time if you had them installed seperate.
Mine also rattles when it is cold. It sounds like something is loose inside or something. If I hit it with my hand I can also hear it. It has done this for about two years and it passed smog in CA so it probably is still okay. Unless you want to replace it (like I do) let it go because they are expensive. Also as mentioned, you would be smelling a "rotten egg" smell.
The catalytic converter or "cat" is made of a ceramic material and is held inside the steel casing. Heating and cooling can cause the "cat" to get a little loose inside. Replacement "cats" cost in the $90 - $120 range for replacements similar to stock. These are 3-way "cats" which is supposed to reduce NOx to nitrogen and oxygen using the small concentrations of unburned gasoline vapors in the exhaust - however, this same process can convert sulfur dioxide to the smelly hydrogen sulfide (smells sort of like rotten eggs). So the rotten egg smell means that there is not enough oxygen in the exhaust gas to oxidize the hydrogen sulfide to sulfur dioxide. And this implies the oxygen sensor is not working OK as this O2 sensor is what the computer uses to adjust the air/fuel ratio. Why am I going on about this? Because this rotten egg smell is more likely to indicate a sickly O2 sensor than a bad "cat". If the "cat" is dead, it will not convert sulfur dioxide or SO2 to H2S and give the rotten egg smell. The 3-way cat designation comes from a "cat" which works to reduce the concentrations of 3 air pollutants, carbon monoxide, nitrogen oxides or NOx, and hydrocarbons. Sorry about running off at the mouth so much about this! Have a good day. By the way, if the "cat" has excessive pressure drop indicating it is plugged, then it is time to replace it even if it does work sort of OK. Not an easy way to measure the pressure drop but others have posted how they did this (need to tap into exhaust pipe upstream of the cat). Mike with 91XLT 4x4 in Seattle.
My dad had a similar problem with his 88 Taurus and I kept driving the car. Unfortunately after 750miles, the car ignited into flames and luckily I escaped with no injuries. Just Kidding.
His Catylitic converter shield did fall off on the highway though b/c it was loose and therefore producing the clanking noise. Get under the truck and see if you can wiggle the heat shield - I bet that's your problem for sure. Also check the bolts that adhere the cat to the Y pipe.
If this doesn't work, then call Summit Racing 800-230-3030 - I picked up my high-flow cat two years ago for 79.00.
I know you have probably already checked, but it could be the heat shield that is rattling....I know the heat shield for my tailpipe (right above the axle) rattles on the shock absorber sometimes, and you would swear that it is a loose part in the muffler...
The factory cat should be good for about 100K miles as far as it's performance (I think it is federal law that cats last that long?)
