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E34 (1989 - 1995)

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  #1  
Old 12-27-2012, 08:49 AM
S406 S406 is offline
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Mein Auto: 00 S4, 93 525i
Bad gas mileage at ilde?

On my 93 525, I wasnt positive on which way the cluster needle for the gas mileage is suppose to go. But it seems as though I get horrible mileage at idle. It goes to the 0 side instead of the 40 side. Is this correct? im averaging between 15.9 and 17.4mpg with almost all hiway. The exhaust has an odd smell sometimes like I have never smelled before. Not coolant, rotten eggy or a rich smell. Its smells chemically kinda. Ive been working on cars for 20+ years and have never smelled anything like it.

The valve from the brake booster to the intake has a nipple on the underside that is broken and sucks air into itself. Is it suppose to be plugged or is it suppose to take air into it? Is there a hose that is laying out of site that has broken off of it?
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  #2  
Old 12-27-2012, 09:16 AM
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r33p04s r33p04s is offline
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Miles per gallon...if you're not moving at idle it will be 0, coasting at idle it will go the other way...come on now

I believe rotten eggs mean a dead cat

Maybe someone can help with the booster...probably should have a line connected
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  #3  
Old 12-27-2012, 09:21 AM
S406 S406 is offline
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lol Thats what I kinda figured. But my audi is the opposite and a 325ix Im working on goes to the 40mpg side at idle. Not a rotten egg smell...
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  #4  
Old 12-27-2012, 05:14 PM
snowsled7 snowsled7 is offline
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If the car is not moving, you are getting 0 mpg. The gauge is working correctly

First thing I would do is repair the vacuum leak at the booster. Then before I condemed the cat convertor I would be looking at an O2 sensor. Before that I would be looking at tune up items like plugs, wires, injectors.

Your milage seems a little low for an M50 525. Could be a lot of things, heavy foot, auto trans, even a small amount of stop and go mixed in, or what you city folk consider highway driving sometimes

My 535/5 averages about 24, mostly highway, but I run it hard too, everytime it goes out.

We really need a whole lot more info to be much help.
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  #5  
Old 12-27-2012, 06:10 PM
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Radian Radian is offline
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If it smells like a fire-cracker...that's the combination of nitric oxide and nitrogen dioxide (NOx). It's from running near or too lean. Any significant vacuum leaks or deficient fuel delivery would definitely be suspect.
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  #6  
Old 12-27-2012, 06:48 PM
robertobaggio20 robertobaggio20 is offline
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Quote:
Originally Posted by S406 View Post
On my 93 525, I wasnt positive on which way the cluster needle for the gas mileage is suppose to go. But it seems as though I get horrible mileage at idle. It goes to the 0 side instead of the 40 side. Is this correct? im averaging between 15.9 and 17.4mpg with almost all hiway. The exhaust has an odd smell sometimes like I have never smelled before. Not coolant, rotten eggy or a rich smell. Its smells chemically kinda. Ive been working on cars for 20+ years and have never smelled anything like it.

The valve from the brake booster to the intake has a nipple on the underside that is broken and sucks air into itself. Is it suppose to be plugged or is it suppose to take air into it? Is there a hose that is laying out of site that has broken off of it?

Have you tried pulling the error codes via the stomp test ?
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  #7  
Old 12-28-2012, 06:57 AM
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BMWFatherFigure BMWFatherFigure is offline
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Mein Auto: E23;E30;E38;E32;E34 +
Does the broken part pull air all the time? If so fix it.
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  #8  
Old 01-03-2013, 11:36 AM
fryntyr fryntyr is offline
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Mein Auto: 1991 BMW 525I
If you do the O2 sensor, spend the $15-$20 and go ahead and swap out the Coolant Temperature sensor as well. The CTS is what was causing mine to cough at idle (sometimes die) and have worse gas mileage. I was back up to 25-26 hiway on my 91 525 before it got wrecked last night with the CTS change. In prior weeks I fixed many vacuum leaks and cleaned the ICV which helped but didn't cure it.
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