It is difficult to start my BMW it runs rough and smells like raw gas from the exhaust pipe. My check engine light is on.

What could be the problem?

I just had the engine replaced I am over 8,000 dollars into this car! There is about 89,000 miles on this engine. Please help! Don't know what to do, at this point I'm feeling like junking it!


  • Welcome to the site! Hopefully someone can assist. Apr 23, 2016 at 22:46
  • 2
    Damn, $8K. Anyhow, answer the following: With the car in park or neutral, does black smoke come out the tailpipe if you step on the gas pedal hard? Does the car consume a lot of fuel? Have you ever replaced the catalytic converter?
    – race fever
    Apr 23, 2016 at 23:01
  • 1
    Have to connected a code reader to the vehicle to read the engine code? If so, what engine code is causing the engine light to come on? Apr 24, 2016 at 3:25

3 Answers 3


The fact that you can smell fuel in the exhaust is a strong indication that the engine is running rich.

This means that there is more fuel than required by the engine. There are many things which could cause this and the sensible course of action would involve hooking the engine computer to a scan tool to retrieve data about fuel trims, and O2 sensor health.


Sounds like a possible evaporative system issue involving the purge valves that vent fuel vapor from the gas tank. If the OBDII -on board diagnostic code that triggers the check engine light is P0440 then that is the issue. If the purge valve remains open for too long it will eventually damage the catalytic converters by sending too much unburnt fuel directly onto the catalytic elements overheating and melting them and eventually blocking the exhaust. This issue would cause rough idling, difficulty starting when hot or stalling etc. The purge valves normally vent the vapor when accelerating and would be closed normally.

Evaporative systems can be triggered by a loose or missing gas cap.


Anything to do with FUEL, especially if the smell is strong should be dealt with immediately. I would suggest to just bring the car to the dealership and let them run a diagnostic on the car. Then you will know for sure if the problem is a easy fix or something worse.

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