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Thread: Problems huge horsepower loss

  1. #1
    Join Date
    Jul 2020
    Location
    Alabama
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    1
    My Cars
    03 325i

    Problems huge horsepower loss

    Ok I have a 03 bmw 325i it's my first BMW I havnt owned it long at all but I really like it and come to realize the quality of craftsmanship BMW puts into there cars. Anyways it has like 230000 but always rans great I drive it anywhere. All of a sudden I have noticed a huge horsepower loss plus I believe I need to replace the vanos things it's been having the 3000 rpm stutters but it hasn't been bad enough or a problem really for me to fix but now I got to fix what's wrong. I diagnosed it and got the following codes and they really don't tell me whats wrong or I don't understand them enough so I figured one of you guys could pin point what exactly needs fixed replaced. The codes it gave me are : P0430 P0461 P0305 P0313 P0304 P0300. Any help or advice is appreciated thanks guys

  2. #2
    Join Date
    Apr 2020
    Location
    Wentzville,MO
    Posts
    15
    My Cars
    2004 BMW 325i 2.5L
    I would start with your exhaust manifolds, fuel pump maybe, and change out your plugs and coil packs. One of your codes is for an engine cylinder misfire and the others sound fuel related and catalytic converter related

  3. #3
    Join Date
    Jan 2015
    Location
    Timaru, New Zealand
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    1,132
    My Cars
    Two Z3 Roadsters
    You have a scanner, that's good.

    Lots of misfire codes. Misfires are usually caused by lean conditions. Do this testing with your scanner. With a hot engine at idle, check the 4 fuel trims, 2 short term and 2 long term. If any are > 8% then you likely have vacuum leaks. Rev the engine to 3,000 rpm for 30 seconds and watch the short term fuel trims. If they reduce significantly, might even go negative, then its confirmed that you have vacuum leaks to find.

    P0430 is about blocked cats. I don't know how to test the cats with a scanner. If your problem is not vacuum leaks then take the car to a shop to get the cats checked.

    P0461 is about a fuel gauge error. Learn how to use the hidden tests in the instrument cluster. In the hidden tests, it will tell you the fuel tank level on both sides of your tank and the fuel level that is displayed on the gauge. They should all be about the same. If not, then one of the tank gauges needs to be replaced.
    1999 2.8L Z3 Roadster,
    2000 3.0L Z3 Roadster,

    There is only one thing more pleasurable than working on a Z3, that's driving it top down on a fine day.

  4. #4
    Join Date
    Jun 2012
    Location
    New Mexico
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    915
    My Cars
    2003 328i
    Don't worry about the cat efficiency codes until you sort out the fuel trims and misfires.

    At the age and mileage your car is it there is a long list of things it probably needs just as far as maintenance. Pull the entire intake manifold, replace the intake gaskets, vacuum lines, crank vent valve and pipes, rebuild the DISA valve, replace the coolant pipes and oil filter housing gasket. Put it back together with new intake boots. Wouldn't be a bad idea to replace spark plugs too. There is a good chance that will fix your problem.

    If this car is like most other e46's you probably need to replace the cooling system as well. Most people just run them until something explodes. At a minimum, it needs a water pump, thermostat and expansion tank. Use genuine BMW parts, aftermarket stuff is garbage. Lot of cheap crap and counterfeit parts made in China but marketed as OE. Buy your stuff from a dealer and get it through a legitimate supply chain and you will get good stuff that will work properly and last a long time.

  5. #5
    Join Date
    Jul 2011
    Location
    Arlington, VA
    Posts
    9,933
    My Cars
    2018 BMW M240i
    To add to no turbo Dan’s excellent advice: The installation of aftermarket cooling system parts is strictly verboten. Go to FCPEuro to buy cooling system parts that are marked “OE” (original equipment: the part is made by the supplier of the part to BMW). Btw, the only brand of expansion tank to buy is MODINE. Make sure you buy a block coolant drain plug crush washer or else you’ll have leaks. Fcpeuro provides a lifetime warranty for everything it sells!

  6. #6
    Join Date
    Apr 2013
    Location
    Mill Valley, CA
    Posts
    346
    My Cars
    2003 330cic
    Quote Originally Posted by nonturbodan View Post
    Don't worry about the cat efficiency codes until you sort out the fuel trims and misfires.

    At the age and mileage your car is it there is a long list of things it probably needs just as far as maintenance. Pull the entire intake manifold, replace the intake gaskets, vacuum lines, crank vent valve and pipes, rebuild the DISA valve, replace the coolant pipes and oil filter housing gasket. Put it back together with new intake boots. Wouldn't be a bad idea to replace spark plugs too. There is a good chance that will fix your problem.

    If this car is like most other e46's you probably need to replace the cooling system as well. Most people just run them until something explodes. At a minimum, it needs a water pump, thermostat and expansion tank. Use genuine BMW parts, aftermarket stuff is garbage. Lot of cheap crap and counterfeit parts made in China but marketed as OE. Buy your stuff from a dealer and get it through a legitimate supply chain and you will get good stuff that will work properly and last a long time.
    Agree with all of this except I would say anything marked as OE on FCPEuro is a perfectly acceptable alternative to genuine. There is zero reason to buy genuine if OE is available - note this is not the same as OEM

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