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post #1 of 4 (permalink) Old 04-05-2006, 12:14 PM Thread Starter
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Terrible gas mileage/ performance

1995 740i e38 ((109000 miles)) w/ k&N filter (only mod)

The car's performance has slowly been declining since i bought it about 7 months ago.

****OIL LEAK****
The car has an oil leak on the left side of the engine. When i drive on the highway a tiny bit of smoke and a very foul oil odor comes out of the engine bay. I have had the valve cover gaskets replaced about a month ago but there is still a leak somewhere. I am guessing it is leaking onto the exhaust manifold and that is causing the smoke but im not sure. When i turn the car on, i occasionally get white smoke comming out of the exhaust for about 5 seconds.

****Poor gas mileage and acceleration****

I am getting an average of 12 to 13 mpg including highway driving and i know this is definately NOT what this car is supposed to be getting. When i turn the car on, i can sometimes smell a very rich gas smell comming from the exhaust. The car does not accelerate as well as it used to and hesitates sometimes. Oxygen sensors or possibly more than that?

Is it possible that the oil leak has fouled out my spark plugs? I had them replaced about a month ago, but dunno if thats causing the poor performance.

Any suggestions would be appreciated
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post #2 of 4 (permalink) Old 04-06-2006, 01:07 AM
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I would deffinatly start by checking the spark plugs, if you are smelling gas and you had an oil leak it could have deffinatly fouled your plugs...If you have fouled plugs this could affect your performance...Start there and work your way up. Good luck

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post #3 of 4 (permalink) Old 04-06-2006, 03:26 AM
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Have you had the fault codes read? Your local dealer has the equipment to check if there is something recorded in the cars computer. I'd not be amazed if you would find that some lambda-sensor is broken, that would partly explain the bad fuel economy.

Check all gaskets to see where the oil is pouring from. I know by expriance that the smell isn't a delight.. Everytime some one enters the car it's the first comment.


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post #4 of 4 (permalink) Old 04-19-2006, 02:17 PM
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Saw this - might help

I am doing some prepurchase research on a 740iL and literially just came to this forum from another that talked about a problem with idenitical symptoms. Check it out.


Could explain the left side oil leak, smoke, poor performance, etc.

Hope it helps!
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