Fuel smell in the cabin

Hey everyone.
I did search, but most of the threads are about e36 and e46, no specific info about our cars:(
I noticed this problem a few weeks ago but i thought it was coming from outside. But now it smells like fuel inside the car with windows up and driving. I do have catless x-pipe, but there was no smell for a few month after we installed it. There are no codes or any other warnings, just a bad fuel smell. Have to drive with windows down lol.
No leaks that i can see without removing anything, but i would like to get some feedback on this. Anyone has an idea what may be causing this?
I will try to fix it myself if its something simple, if not will take it to my shop.
The car is e92 M3, out of warranty.
Any feedback will be appreciated.

I had this problem as well. Catless but no in cabin smell for months. Then it suddenly started smelling. I can't tell you why since I just swapped to high flow cats instead.

If the smell is raw gasoline not burned exhaust then look at the first post here:
http://www.m3post.com/forums/showthread.php?t=694148&highlight=fuel+pressure+sensor

I seem to remember that someone else posted about a leaking fuel pressure sensor. The sensor is located near the fresh air vents/filter housing to easily allow the smell into the cabin. You will need to have the engine running to pressurize the fuel system. Where the plastic meets the metal housing of the sensor is where these types of sensors often leak.

If the sensor stays dry inspect along the fuel rail and injectors.

A leaking fuel system can make a big fire don't wait to inspect under the hood.

kenwelch wrote

If the smell is raw gasoline not burned exhaust then look at the first post here:
http://www.m3post.com/forums/showthread.php?t=694148&highlight=fuel+pressure+sensor

I seem to remember that someone else posted about a leaking fuel pressure sensor. The sensor is located near the fresh air vents/filter housing to easily allow the smell into the cabin. You will need to have the engine running to pressurize the fuel system. Where the plastic meets the metal housing of the sensor is where these types of sensors often leak.

If the sensor stays dry inspect along the fuel rail and injectors.

A leaking fuel system can make a big fire don't wait to inspect under the hood.

It smells more like exhaust fumes. Similar to what i smell when i stand behind my catless car with engine running. I will look at this sensor tomorrow, but i dont see any codes thrown, engine runs normally, no loss of power or limp mode.
Can it be some exhaust leak from the connection between the header and x-pipe? Will be there any codes thrown in this case?

I would start with the x-pipe. If you can put the car up on a lift with the engine running you might be able to feel the leak. Sometimes you can see the carbon (like the black on the exhaust tips) trail at the leak point.

There is also a diagnostic device called a smoke machine that can be used with the engine off and the CATs cold. The smoke machine produces theatrical smoke the will be easily seen with a bright light. This is the method that I like for locating exhaust and vacuum leaks. Google "smoke machine for cars" there are videos showing the device in operation.

The exhaust smell is important and might indicate that you are likely breathing carbon monoxide so keep working on a solution!

If you do not find leaks in the exhaust system then check the trunk seal. It is possible for exhaust fumes from the tail pipes to be drawn back into the cabin. With the front windows down a vacuum can be created that allows exhaust to be pulled back in on station wagons and SUV's with the rear hatch window open. A damaged/leaking trunk seal works the same way.

My guess is that your exhaust mod is the most likely source of the smell.

Carbon monoxide is odorless and tasteless FYI. The smell is basically byproducts of fuel being burned.

True, but when mixed with with other exhaust by-products it's a good reminder to get it fixed OR stop breathing.

So i went to work today with my m3(not a daily driver) and there was no smell at all I drove normally for the first 10 miles and then started to push harder and harder, but no smell. I dont know should i be happy about it or not. Already made an appt. with my shop that installed that x-pipe. Will report back about his finding.

You might have some oil somewhere in the engine bay. Happened to me. A little different situation but some oil had accumulated on my recirc value (my car is supercharged and some of the blow-by had accumulated on it) and the oil residue smelled of gasoline. The smell wasn't bad with the hood open but with the hood closed you could smell it through the passenger cabin. Once I figured it out I clean it and viola no more smell.