Gas smell from exhaust on cold start up. How do I read the fuel trim?

[SuperAkumaGT]

Long time user under a different account because I lost my password to the original account (superakuma). 

 Car
2011 Subaru Legacy 2.5i 6MT with about 180k on it. 

I don't drive the Subaru as much because my cousin gave me his 2000 accord, but I still drive it from time to time(at least once a week and short distance) If I am not driving it, it sits in my garage. 

The last time I drove it was 2 days ago. Today I moved the Subaru from the garage to the street and had 2 hard start. I waited 20 sec or so to start the engine and got it on the 3rd try. After I moved it to the street, basically down the driveway, my whole garage smelled like gasoline. The gas smell is mainly from the exhaust. I popped the hold and the engine bay does not have any gas smell. No smell from the inside of the car either, only the exhaust. 

This has been happening for a while and only noticeable at cold start up.  After driving for a while, you can't smell gas coming from exhaust. 

NO CEL
I have the BlueDriver OBD reader and the only code I pull are related to the ABS which I don't think has anything to do with this. 

I did a little research before posting this and some people said to check the fuel trim but did not find anything on how it is supposed to look like or what to look for. I do have an OBD reader that will give live data. 

What else should I look at or test for? Read below for history that may help figuring out the problem. I think this has something to do with the really bad gas mileage I've been having. 

 

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History if issue that I think maybe related
Winter I noticed that I started to get really bad gas mileage. Normally I get about 25mpg easily driving on the street and 34mpg on the freeway. (I don't drive crazy). Last winter I noticed that I got around 20mpg on the street. Right now gas price in Cali is close to $6.50 gallon. 

During that time and now I replaced/tuned up the car

-oil change
-new spark plugs
-PVC Vavle
-cleaned TB
-Cleaned MAF sensor

 

Edited October 8, 2022 by SuperAkumaGT

[DrD123]

the fuel trims (short term and long term) are how the ECM has adjusted the fuel into the cylinders to operate properly - ideally, short term and long term should be small, and close to zero (short term will jump around a little, you generally should see something under 5 or 10%.  If the car is running rich and the fuel trims are high, then the engine thinks it's getting less fuel or more air than it actually is - assuming the MAF sensor is reading properly, and the plugs are good (there are counterfeit NGK plugs out there that give less than ideal results, could be one of your o2 sensors are reading incorrectly ( the car is 12 years old, give or take, with a bunch of miles, so certainly wouldn't be a surprise for one to go) - if they are large and negative, maybe you have a bad/leaking injector...

if you don't stick to top tier gas, then it wouldn't hurt to run some injector cleaner through (techron, etc.)

[dgoodhue]

I think the gas mileage change is significant. The O2 sensor is the feedback senor for the closed loop and it has significant affect on the fuel trims.   I am not normally into changing parts randomly but perhaps the O2 sensor is going bad or out calibration. 

[SuperAkumaGT]

Sorry for posting a question and no responding. I forgot I made this post. 

I think I may have found the problem or a new problem. I found oil in the spark plug. Would that cause the problem? I will post another question in regards to that with some more details.

Thanks DrD123, I will do a test drive this weekend with my reader and post the results. 

[DrD123]

Oil in the spark plug tubes just means the gasket where the tube meets the valve cover is leaking.  Only solution is to replace the gaskets (you pull the valve cover and then replace the two spark plug tube seals and the valve cover gasket - it's a little awkward because it's a subaru and the valve covers are on the sides of the engine, but not hard.  If the oil were messing with a cylinder, you'd have a misfire (flashing CEL and a P030x where x is the cylinder misfiring)

[SuperAkumaGT]

No miss fire or CEL. 

For future reference for anyone who found this though a search, anything related to the oil in spark plug will be talked about here. 

If this was the caused of the gas smell from the exhaust I will update it on this thread.

[silverton]

Too much oil in the spark tube seal and your spark plug wont fire.