'99 Legacy - smell of unburnt gasoline from exhaust

Does it smell, like rubber or oil or 'toasted marsmallows' or ??? Is there any smoke? Are the fluid levels OK? CV joint boots intact?

Carl

Could be an issue with injectors. In a cold-cycle, the ECU ignores the O2 sensors and tries to guestimate 14.2:1 AFR. Once it warms up and starts paying attention the the O2 sensor, everything should be normal. Other than being a bit annoying, it probably won't do anything bad.

I think this is actually normal. If the engine is cold, the car will run rich. That is part of the startup algorythm,for the ECU. If it continues after a few minutes of running, then you might have a defective temperature sensor, I wouldn't worry about it.

Bill

I've never noticed it with any of my other cars...

/MM

It smells gasoline, I don't have a better word... With regards to the smoke, I would say it looks more like dense steam, it doesn't seem to leave any marks on the bumper... The fluids are OK, the boots I believe are too, and I am talking about the car sitting in the driveway anyway...

/MM

When was the air filter last replaced?

If it only does it when it is cold outside, then I BELIEVE it is because the car senses that it is cold, and runs the engine a little richer, which helps with cold starts. Both my 95 legacy and 90 miata do this. The exhaust looks like steam and smells of gas. The legacy has done it since I acquired it in 2001. It always passes emissions, and only occasionally has the CEL on, which is pretty good for a subie.

Once the ECU exits the startup sequence, the car will run closer to stoichiometry. This rich-running during the start up sequence is why 'the experts' say it actually wastes gas to shut your engine off at a stop if it is going to be off for less than 70 to 90 seconds.

The reason it is worse in cold weather is the colder air makes it harder for the injectors to atomize the gas small enough to fully combust. So you get unburnt fuel. This is actually the reason that they need to put more fuel in-to make up for all the stuff that won't burn. Once the head gets up to temp, the incoming air is warm enough that the fuel will vaporize more easily. Consequently the smell of gas goes away, and the extra fuel is not needed, which means the ECU sends less gas. So then the exhaust stops smelling like gas.

I can't back this up with any sources, just a compilation of what I have heard here and there. I really don't think there is anything to worry about though. Cars simply run rich when the engine is cold.

I hope you are right, but none of the cars I've owned did it, or at least not to the extent of this Subaru. And I owned Toyotas, Honda, Acura, and Mazda... In fact I have a 2000 Honda Civic now and there is no comparison... I probably should have mentioned that I believe that the fuel consumption on this Subaru is too high. I am not confident because it has the infamous intermittent speedo problem, which makes trip meter readings bogus. I am working on getting that fixed, but I do have a feeling that I am at the pump too frequently.

/MM

Good question. I've just bought this car recently, so I will have to take a look at the filter, although it hasn't popped up in the pre-sale inspection, so it is probably OK.

/MM

It may be a good idea to have the Engine Temp Sensor (not the temp gauge sender) tested or changed. It can fail in such a manner the engine is in 'choke' mode all the time. Though people usually complain of poor running after warm-up, it cerainly would use excessive fuel and may not activate the check engine light.

Carl

I agree with Carl that if it goes on for too long after the car has started, then the sensor might be bad, and causing the engine to stay in the start-up mode. My wife's saturn had a bad temp sensor, and it caused nearly impossible warm starts. I know it is a different car, but if you have difficult warm starts, then perhaps the temp sensor is bad.

I just looked at your original post. I read it and asumed you meant one thing, but you coudl mean another. You say that it does it until the car "warms up." I assumed that meant after the first minute or so it goes away. If you mean it goes away after about 5 minutes of driving, when the coolant temp gauge is well past the lowest mark, then that is too long.

If it is taking a few minutes, then it is probably only going away because the engine is warm, and able to burn the gas more efficiently, thereby creating less unburnt gas in the exhaust, but still running rich. It is not because the ECU has cut the amount of gas going in, only because the gas is burning more efficiently. If this is the case, I'd suspect the temp sensor that Carl mentioned.

Good luck, Bill

Thanks to everyone for all the advices. Are you talking about the coolant temperature sensor (as shown here

or is there another temperature sensor? I will have to pay more attention to how long it takes for the smell to disappear, but I believe it is there for quite a bit more than a minute... It is difficult to judge though as after a minute one's nose loses its sensitivity :)

Thanks, /MM

Hmmm...not sure. that is a '95 and may not have an ENGINE temp sensor. usually, the 2 are near each other but i THINK the ETS has 3 wires. The Coolant 'sender' has 2 (or maybe one plus ground?)

someone may know more about the physical aspects of this.

There are several ways the ECU can be confused and use too much fuel. MAF , O2, engine idle solenoid(IAC?), maybe vacuum leaks, etc. for instance. But if there is no CEL or OBDII code stored (that also returns quickly when cleared) then I'd suspect the Eng. Temp Sensor.

Carl

Same here with an '08 Outback 2.5i

The colder it is, the more it smells. (And this Winter it was really cold ...)

Also, while the automatic transmission is in 'P', the motor RPM is quite high. It goes down as soon as I shift to 'D'.

I always thought that this could have to do with the LPG add on, which Subary gave away for free to new car buyers last year here in old germany. LPG costs 65 ct., while Gasoline costs 120 and more, so while fuel consumtion is 10% to 20% higher with LPG, this is still a big win. It is clear that I drive with LPG whenever possible. Still, the motor will be in gasoline mode when started and remain so until it reaches a certain temperature.

While not able to give a detailed technical description of how it works I would say that with the transmission in P there is no load on the engine. When shifting to D it loads up the transmission ready for the vehicle to move off. You would get the same lowering of revs if you were in P and loaded the engine by switching the Air Conditioning on high.

Sounds reasonable. Thanks for the hint.

I just hold the throttle to the floor for about 45 seconds!

(NO, not really!)