I'm going to ask one of those "almost impossible to diagnose over the net" type of questions as it involves sound.

There is a rattle.. not a clunk, but a dull plasticky sounding rattle coming from perhaps the front end, maybe sometimes the rear end as well, that occurs when traversing rough roads or going over small bumps faster than 5 mph. The rattle sounds like maybe something's loose; perhaps something in the suspension system. Could possibly be the strut mounts? Apart from the noise, I don't notice any adverse affects when driving. Can't hear the rattle with the windows down, only with them up and the radio off. At first I thought it was something in the cabin, but it seems like it's coming from under the vehicle. What's a good way to diagnose? Any suggestions?

 

Could be your catalytic converter. They have the tendency to make a very disturbing noise when they go bad.

 

Been there done this. There is a plate with a single screw that holds both sides of the exhausts together . It needs to be tighten . It's about front doors seam lengths down.

 

Thanks for the suggestions guys. I'll put the car on stands next weekend and have a poke around. Hopefully it's as simple as the bolt holding the exhaust support/plate on.

 

A lot of rattles are caused by loose exhaust heat shield mountings.

Nick

 

Thanks Nick. I'll give everything a thorough once-over while I have the car on stands next weekend.

 

did you find what caused the rattle noise?

 

Actually I did. Turned out to be front torque arms and lower control arm ball joints. The rubber dust boots aren't torn and are still in good condition, but enough slop has developed that whenever I traverse uneven road surfaces, it causes them to rattle.

I guess this will be my next winter project. Looking at the front suspension configuration, it doesn't look too difficult to swap out those parts.

 

Thanks,
I've been hearing the rattling when it's idling sometimes just right starting the car or sometimes parking the car rolling windows down to hear it. Dealer told me the Cats. some days loud... some days quiet... yet they are indeed need to be replaced.

 

Could be the cats in your case. In my case, I don't get any rattles unless the car is actually moving.

 

If the cats are bad check your laws.. there is a longer warranty on cats.. here in California I believe they are ten years or more

 

Only pzev cars get a 15 year /150k mile warranty

https://www.arb.ca.gov/msprog/warranty.pdf

Just 8 years /80,000 miles on cats in California and every other state , that's a federal warranty

 

"pzev"? A new acronym for me, so I had to do some research...

"The California Air Resources Board (CARB) created the PZEV (Partial Zero Emissions Vehicle) category in 1998 as part of the state's vehicle emissions laws, which at the time were stricter than the rules at the federal level. In 1998, electric cars and battery tech weren't what they are now. But, a Honda spokesperson tells PM, "we could meet the same emissions with an internal combustion engine as a battery-electric when taking into account the upstream power plant emissions." As Dave Barker, Subaru's energy and environmental activities manager, tells us, "tailpipe emission standards for our PZEV vehicles are approximately 80 percent lower than the standard for our counterpart vehicles."

They're also easier to make. Creating a hybrid or pure EV version of a car requries significant changes to the design, such as carving out room for battery clusters and redoing suspensions to fit wheel-hub electric motors. Creating a non-hybrid PZEV is less disruptive. These cars have the same engines and transmissions and are built on the same platforms.

There are three unique components in the fuel systems, and one in their exhaust, that makes a PZEV:

Anti-Permeation Fuel System Liners. When fuel system components get saturated with gasoline, they leak gas vapor through the outer surfaces, letting it evaporate into the air. So, engineers building PZEVs line the insides of fuel caps, fuel hoses, seals, gaskets, and plastic fuel tanks with layers of low-permeability polymers such as ethylene vinyl alcohol to keep fuel from soaking through. This stops off-gassing as the vehicle sits unused. "If you'd have walked around a parking lot in California ten years ago you could smell gasoline," Honda says. "Today, not so much."

Carbon Canister Scrubbers. Temperature swings from day to night can cause gasoline to evaporate past the fuel cap and into the atmosphere. Refueling also forces gasoline vapor out the system and past the gas pump nozzle. To capture gas before it reaches the air, a car fixes a canister of activated carbon (carbon that's processed to be more porous) in the fuel-filling line from cap to gas tank. The canister traps most of these hydrocarbons, which the engine destroys by pulling them into the combustion chamber. Even so, the canisters still leak small amounts of vapor. PZEVs add an auxiliary scrubber canister of honeycomb-shaped carbon that captures 95 percent or more of the vapor leaking out the primary canister.

Carbon Air Intake Trap. After you shut off an engine, fuel vapor remains in the combustion chamber and intake manifold. That vapor evaporates, and like with the carbon canister, a filter of activated carbon grabs outgoing hydrocarbons before they can make it into the surrounding air. Newer designs are using a metal honeycomb filter spread with zeolite, another porous filter mineral.

Close-Coupled Catalytic Converters. Catalytic converters are part of any fuel-powered passenger vehicle sold today. Exhaust gases pass from the engine through the converter, which is lined with precious metals such as platinum, palladium, and rhodium. These convert much of the pollution gases into less harmful gases.

PZEVs mount two catalytic converters closer to the engine than a conventional design does. Emissions are dirtier when a car first starts up and the converters are cold; the engine's radiating heat brings close-coupled converters up to operating temperature more quickly. After the converters the two pipes converge into one, and exhaust passes into a third catalytic converter under the passenger cabin. This third converter cleans up nitric oxide and nitrogen dioxide, two building blocks of smog and acid rain.

WHERE ARE THEY?

To be clear, PZEVs reduce emissions that lead to problems like smog. You're still burning gasoline that contributes to woes like the greenhouse effect. Honda puts it this way: "PZEVs are valuable for reducing pre-cursors to smog-forming emissions (such as carbon monoxide, nitric oxide and nitrogen dioxide [both NOx], and non-methane organic gases [NMOG]), which is a local phenomenon … They do not reduce greenhouse gases, which are not local but rather global. … A typical EV generates 258 milligrams of NOx and NMOG per mile on the U.S. electrical grid or 120 milligrams per mile on the California electrical grid, roughly nine times and four times the PZEV level. Of course, as the grid gets cleaner, so too will (EV) emissions.""

BTW -If you were not aware, most of our W220s are ULEV (Ultra Low Emissions Vehicles).