2005 Mitsubishi Endeavor

Hi McGrifken. Welcome to the forum. Two things can cause that smell. The exhaust system is one, but an overcharging battery is more common. The next time this happens, leave the engine running and jump out of the car, (put it in park first :)), and use a cheap digital voltmeter to measure the voltage between the two battery posts. It must be between 13.75 and 14.75 volts. If it is higher than around 15 volts, the water will start to boil out of the battery and will eventually lead to the smell. Continued overcharging will destroy the battery.

Also smell the exhaust right by the tail pipe to be sure that isn't the source of the stink.

Caradiodoc

Dandy. That rules out battery and charging system problems.

The Engine Computer is constantly changing the fuel mixture from too rich to too lean a few times per second. When it goes lean, the unburned oxygen is stored in the catalytic converter. When it goes too rich, the unburned fuel mixes with the stored oxygen and is burned. Acceleration requires a richer mixture so more fuel is being burned in the converter. That increases the concentration of that wonderful smell. Too much unburned fuel from other causes such as a leaky injector, leaking fuel pressure regulator, or a misfiring spark plug can cause overheating of the converter and the smell. There are sanitizers, or odor eliminators for catalytic converters but I've never used them or heard how well they work, but normally the cause of the overheating must be addressed first, then the converter is replaced if the smell doesn't clear up. If just the converter is replaced, you run the risk of the same thing happening to the new one.

Caradiodoc

Don't know about other manufacturers, but if you bring a Chrysler in to the dealership, the complaint will be documented, even if it doesn't act up there. They will warranty previously-documented problems for many years and miles after the warranty expires. Wouldn't hurt to ask if they'll still handle yours under an extended warranty.

Catalytic converters are kind of hard for a do-it-yourselfer to replace, but not impossible, but you need to stop what is causing it to overheat first, if that's what is happening. Also check for a severely overcharging battery. Sniff around the tail pipe and the battery to find out where the smell is coming from.

Caradiodoc

Rattling heat shields can be tack-welded with a wire feed welder. A simple do-it-yourself trick is to band it with a large screw-type hose clamp. Use two of them, end-to-end, if you need a longer one. If that holds the two halves together yet lets them rattle over the pipe, simply bend them a little flatter to remove part of their curve, then clamping them will hold them tighter to the pipe. Another trick is to wedge a piece of metal through a hole or through a slot you cut in the shield to take up the gap between the pipe and shield, then clamp it in place with the hose clamp. Also, if you can find a soft spot, typically due to rust, you can pound in a depression, then wrap the hose clamp around it with a small piece of metal pipe in the depression. The hose clamp will squeeze the pipe to hold the shield against the exhaust pipe. These things work on many import vehicles that have two half shields welded together as appears to be the case in your photo. If you have just one half shield, those are easier to flatten out by hand so the clamp will hold it to the pipe better. The shield in your photo has a smaller diameter on the end where it holds onto the pipe. That is a good place for a hose clamp. First try to bend the edge of the shield up in just a few small spots. That will give the slots in the hose clamp something to bite onto to prevent the clamp from sliding off the shield.

Caradiodoc

Let me clarify about the shields. You have two-piece shields crimped together on the sides. Some cars have just a half shield on the bottom. They are designed to keep leaves away from hot parts. Full shields like yours reduce heat transfer to nearby engine and transmission parts and wiring harnesses. Minor modifications like dents and adding clamps will not have any affect.

One more trick I forgot about that is real easy is to drill about a 1/8" hole in the middle of a shield, then run a self-tapping screw through it. Grind the point off first so it doesn't try to go into the pipe. Also, the point would wear down over time and the shield will rattle again. This only works when the two halves of the shields are still solidly attached to each other.

Caradiodoc