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computer - gas mileage

Discussion in 'E46 (1999-2006)' started by buchmann, Apr 29, 2008.

    buchmann guest

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    On my 2001 325i the computer always tells me I have 405 miles to run everytime I fill the tank. But I can never get more than 270 on the city, 320 on long high-way trips, with the 16 gallon tank, which is not as good as I would like. Shouldn't the computer automatically correct itself telling me the true available mileage based on what it learns or, it does not learn and I should be able to teach the computer somehow? It's my first BMW and I guess I haven't learned all the tricks yet. And I also think I should have it checked to actually improve mileage, as it may need some tune-up or something. It's got 117500 miles and I was planning to take it to the dealer at 120000 but now the check engine soon light came ON so I will have to take it there earlier than planned. I will try the gas cap trick, or at least clean it well with some W40 oil to see if the light goes OFF first. I really don't think the oxigen sensor would go bad just like that. I have it for 6 months when it had just passed through a BMW regular service.

    Dr Obnxs guest

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    Couple items...

    on one of my cars the range always started high and headed lower to converge at the real distance. It was caused by a faulty fuel tank sender.

    Now, for modern cars, the first and most important tool in your tool box is a code scanner. That way you don't have to guess what one of the thousands of reasons was the root cause of your check engine light going on. To use your O2 sensor example, while it's true that they generally go bad slowly, there is a point at which they degrade enough to trip the light so it seems like an o2 sensor failure was "all of a sudden".

    Matt

    buchmann guest

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    O2 sensor - get scanner

    Thanks for the replies.
    I have always taken new cars to dealer for anything that happens under warranty, but this is out with 117k and 7 years.
    I like the dealer service but I am never sure they charge what they actually do, so paying for a scanner may be a way to measure how much I can trust these guys the first time I go there.
    I know for instance their parts pricing is absurd.
    Three weeks after getting the car, the water pump broke. I was lucky I was just entering my garage when I heard a loud crack and I opened the door to see all the bue fluid running on the ground. So I asked the dealer for the price of the pump, $125.00. Got the exact same OEM on the web for $55.00 and installed it myself, and also took the opportunity and replaced the two belts. Three more weeks the fuel pump stopped. Had to tow. Dealer price $500.00. Got a Bosh OEM on the web for $125.00 and installed it myself. So far good savings considering the dealer part price and I can't imagine how much would the labor charge be. But not so good luck with the car. But now, I have looked at my BMW Haynes repair manual, and see that there are 4 O2 sensors, 2 of them for the cilynders 4, 5 and 6 located on the exaust collector that will need to be removed in order to access the sensors. This is way too much for me to do it at home. I am not sure also if one is bad, the dealer will tell me all need to be replaced. It's likely, and it makes sense considering the car's age, but there goes big bucks. But I think I'll get the scanner, and it may tell me it's something else, perhaps on the other side of the tank, the fuel sender is bad, which would affect the computer telling me how much I can run with the full tank, but don't know if would lit the service engine light. I'll keep playing with it for a little while to learn more. At least the car is running like it has always. I do not notice any change at all. And now I know the fuel mileage I actually get is OK. But I'll be carefull, if the sensors are really bad, driving won't tell and bigger expenses will come.

    Dr Obnxs guest

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    Don't forget the independant BMW shops

    One near where I live has the factory diagnostic system. Like you, I only go to the dealer for recall or warranty work. And yes, there are jobs I don't have the tools or time for, and I'll pay someone to do the work on them.

    Start hunting around in your area to find a good shop. You're local chapter members will have some good input about where to go and who you can trust. Many will put in parts that you buy.

    If the O2 sensors are going, you'll loose some gas mileage and maybe a bit of performance, but the car will run fine. But there are tons of things that aren't the o2 sensors that can trip the check engine light. A good scanner is nice to have. Autoenginuity makes a laptop system that can talk "BMW" and access the codes and ddata from lots of other systems. I give it a B-. It's not fast on non-CAN interface cars, but it does let you get info from most systems on the car. The BMW extensions can only be run from a laptop, and they double the price of the system. Generic scanners will get you the code number from the car for OBD-II stuff, but if it's a manufacturers code (I think those are the ones over 2000, maybe 1000, I don't remember) you'll have to do some digging on the web to find out what they mean.

    Anyway, some sort of scanner should be in every car owners glove box or tool box.

    Matt

    buchmann guest

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    OBD-II, wonder what else can I do with it

    Ok, I've set my mind to get one of these tools, and I've been reading about it and it appears that a standard OBD tool would only work to give me information on engine emissions system, but BMW uses the same soquet for a more complete tool that is able to read a lot more information specific to BMW including resetting air bag, oil schedule reminders etc. So I wonder if anyone knows this particular device R5/FCX-3. I have another problem with this car that I was planning to ask the dealer at 120000 miles, to turn ON the alarm which according to the previous owner was turned OFF by request of his father (who used the car before him). I wonder what else this car has and it's not operative and I would like to turn everything back ON. But, would this device be able to do that or is there any other that I should look for, or just the dealer can really do this other proggramming stuff. Even the two keys I have for the car behave differently. One, when used, locks the doors after a few seconds when moving the car, and the other key does not and the doors remain unlocked when I am driving. The seats and mirrors memory position work OK on both keys. What bothers me most is the alarm, I could not find a way to make it work, there is nothing on the manual to turn it ON or OFF, it should just work always as I lock the car from outside with the remote, but it does not, the red light under the mirror never flashes and no beep when locking the car. I just wonder if a more complete and made for BMW OBD tool could give me the options to restore all these features. I think the previous shop who mantained this car had someone either stupid or inexperienced who turned off a bunch of these features by mistake, pushed some kind of general reset, then restored only some. The in-dash Bluetooth connectivity to mobile phone is also disabled. I know a bunch of features are optional and not available on all models, but I was told this car is fully loaded, so I want to check why I don't see some. Definetely, I don't think there is any BMW with no factory alarm installed. Jee! The first time I use this forum and I am already abusing it.
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    shanneba

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    The alarm is optional and normally installed at the dealer. The mirror will still have the alarm light even if the alarm is not installed.

    Most software you can buy for the ODBII interface can not set the BMW "options" such as the door lock when car reaches 5 mph, lock/unlock sound/flash lights. This is normally only available from the dealer.

    I have the Autoenginuity software and love it. I have not had to use it to diagnose any failures yet, but have used it to record data as I drive. It can save the data in an Excel file format. I usually save the Speed, RPM, Ignition timing, injector duration, oil temp, water temp at the engine outlet and water temp at the radiator outlet. I usually have it record these data points every second.

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