Horrible Smell - Exhaust related?

Hi all,

I have an '08 Grand Cherokee Laredo, 3.7L V6 with 74,000 miles on it. Recently the exhaust/muffler have been getting loud, and during my state inspection the guy said it would probably need a new muffler/pipe in the next few months. That was about a month ago. Since then there has been an on-and-off horrible plastic/chemical smell in the cabin some of the time. My wife drives it about an hour to work each way, and she says sometimes it gets so bad she has to open the windows (in 20 degree temps…) or she gets a headache. She describes it as a “formaldehyde smell” and says it tastes kind of sweet. To me it’s more like a burnt plastic/chemical type odor. I checked all underneath but saw no plastic bags or anything else odd. Nothing unusual under the hood. No visible smoke. I have an appointment in two days to have the exhaust fixed. My question is - is there any way this weird smell could be exhaust related? I am hoping so, because otherwise it’s a total mystery. It’s definitely not an “exhaust” smell as I know it.

Thank you!!!


If a pipe has a hole blown open it can direct hot exhaust gasses anywhere under the vehicle.

Since you say the exhaust is loud it means there’s a leak somewhere and something’s getting extremely hot causing the smell.


Agree, your floor carpet liner is probably burning up. My brother in law had this happen with a Ford. Pleas eget it fixed before something really bad happens!

The smell could be the exhaust itself.
If your wife has to open the windows or get a headache, she’s very likely breathing exhaust fumes and this is very, very dangerous at such a high level. Carbon monoxide, a component of the exhaust, when breathed in replaces oxygen in the bloodstream, and low oxygen levels will give a person headaches. She’s very lucky she hasn’t passed out and crashed.

I’m glad you’re getting the exhaust fixed. I urge her to NOT drive this vehicle until the work is done.


The proper way to find exhaust leaks is to use an evap/smoke machine

Not only is this the proper way, but it’s also quite effective and safe

It’s a lot safer than having the car on the rack with engine running, while you put your hand next to various exhaust seals and joints, feeling and listening for a leak

I agree that this has absolute priority. Anybody driving this vehicle is rapidly losing brain cells

Thanks all. We’re aware of the safety issues and have been diligent about venting with the windows down. It’s headed to the shop but good to know the issues are probably related.

Use a smoke machine to find an exhaust leak? No way! The exhaust system isn’t a sealed system.

To find an exhaust leak, start the engine and while it’s idling take something and block the tail pipe. You’ll find the exhaust leak.



I’m speaking from experience

That’s what the large cone on the left is for. This happens to be the machine I use

I’ve found several exhaust leaks this way


But how many shadetree’s have a smoke machine?

I described the shadetree method.



I apologize if I misunderstood . . . but it sounded like you were implying my method was wrong

You said "no way! to my first response

It’s all good, in any case

For what it’s worth, I mentioned the smoke machine, because that’s what OP’s shop might be using if they try to find an exhaust leak

This sounds like a leak the size of which won’t require a smoke machine… only a lift.

Might be loose exhaust flange gasket hardware

That would explain the fumes getting sucked into the vehicle, and it might also explain the noise

If so, retorquing the hardware may take care of the problem