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E46 (1999 - 2006)
The fourth generation 3 Series (E46 chassis) was introduced in 1999 and set the standard for engineering and performance during it's years of production including being named to Car & Driver's 10 best list every one of those years! ! -- View the E46 Wiki

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  #1  
Old 12-06-2011, 06:53 PM
rbrown601 rbrown601 is offline
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Location: Fort Riley, KS
 
Join Date: Dec 2011
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Mein Auto: 2002 325i
HELP! 2002 325i runs poorly, terrible gas mileage

i recently bought my first bmw a few months ago, a 02 325i, and it's started to give trouble. it runs terribly. it vibrates very rough at idle, almost bouncing, & it's difficult to get it to stay on when started for the first time that day. the acceleration is also down the drain. when i start it to go to work in the morning, i could floor it & it'll barely move. it runs better after everything's warmed up, but it's still nowhere near what it used to be. and it's also guzzling gas like there's no tomorrow. can anyone give me any advice or opinions as to what might be going on? i know next to nothing about cars, so any suggestions would help
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  #2  
Old 12-06-2011, 07:26 PM
Variocam Variocam is offline
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Location: Austin, TX
 
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Mein Auto: 2007 328i, 2004 325i
I would start by taking it to one of the major auto parts stores (Advance, Autozone, or Oreilley's), and asking them to read the codes, which they will do for free. Then do a search on the codes that come up. Chances are it's a bad sensor, connector, vacuum leak, or even a broken or loose wire, that's causing the car to run in a reduced-power mode. Good luck.
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  #3  
Old 12-06-2011, 07:38 PM
rbrown601 rbrown601 is offline
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Location: Fort Riley, KS
 
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thanks, i'll let you know how that goes
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  #4  
Old 12-07-2011, 10:13 AM
mujjuman mujjuman is offline
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Location: NY
 
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Sounds like a massive vac leak to me
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  #5  
Old 12-07-2011, 06:43 PM
Variocam Variocam is offline
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Mein Auto: 2007 328i, 2004 325i
Quote:
Originally Posted by mujjuman View Post
Sounds like a massive vac leak to me
Could very well be. It may not even have to be that massive to trigger some sensor to put the car into a reduced-power mode. I had a very small leak which did something similar.
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  #6  
Old 12-07-2011, 07:15 PM
rbrown601 rbrown601 is offline
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Location: Fort Riley, KS
 
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Mein Auto: 2002 325i
so i got my codes read at oreilley's.......p1349 misfire cylinder 4 w/ fuel cut-off. to be sure, i unplugged the ignition coils one at a time & started the car, with the idea that the one that didnt make a difference when unplugged was the misfire.......sure enough cylinder 4 was the one. so i switched coil 3 with coil 4 and now cylinder 3 wasnt firing. so it seems like it's the ignition coil. hopefully this is the problem, but like i said i know very little about cars (even though i work on multi-million dollar aircraft for the army....kinda sad really). any suggestions in case i'm wrong? and mujjuman could you explain the vac leak idea?
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  #7  
Old 12-08-2011, 01:01 AM
KenG KenG is offline
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sound like it is the ignition coil, I would switch the bad one with another one of the coils if you wanna double check
replace all spark plugs too if they have a miles on them

a vacuum leak is a small (or big) hole that lets extra air in, that screws up the fuel/air ratio, but pretty much check your intake pipes (the big u bent hoses that run from your air filter to the engine) and also any vacuum lines
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  #8  
Old 12-09-2011, 10:43 PM
mujjuman mujjuman is offline
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Location: NY
 
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Quote:
Originally Posted by rbrown601 View Post
so i got my codes read at oreilley's.......p1349 misfire cylinder 4 w/ fuel cut-off. to be sure, i unplugged the ignition coils one at a time & started the car, with the idea that the one that didnt make a difference when unplugged was the misfire.......sure enough cylinder 4 was the one. so i switched coil 3 with coil 4 and now cylinder 3 wasnt firing. so it seems like it's the ignition coil. hopefully this is the problem, but like i said i know very little about cars (even though i work on multi-million dollar aircraft for the army....kinda sad really). any suggestions in case i'm wrong? and mujjuman could you explain the vac leak idea?
it could very well be the ignition coil. its not an uncommon problem.

the vac leak is caused by torn intake boots or a bad seal on the DISA valve that lets unmetered air into the intake and messes up the A/F ratio. This also causes the car to have very poor acceleration, like 0-60 in like 15-20 secs and also could cause cold start problems if the vac leak is large enough.

the hissing noise made me think the vacuum leak because when my car had a vac leak, it made a hissing noise too.
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  #9  
Old 12-10-2011, 08:13 AM
Variocam Variocam is offline
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Mein Auto: 2007 328i, 2004 325i
Nice job troubleshooting the coil. Definitely go ahead and replace it (whatever you do, don't buy one from the dealer unless paying triple what something is worth is your idea of a fun experience), and then see if your symptoms go away. My experience has been that vacuum leaks also throw codes, so the hissing you're hearing may be something else. It wouldn't hurt to poke around looking for cracked vacuum lines and the like while you're waiting for the coil, though. And yes, if you're getting up around 100K miles or so, it's time to replace the spark plugs.

Autohausaz has a couple of different brands, and they recommend checking the brand of yours, and ordering the same type. If you buy the plugs from them as well, bringing your total over $50, the shipping is free, too. Pelican parts is another very good source. Good luck.

http://www.autohausaz.com/search/pro...gnition%20Coil
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  #10  
Old 12-11-2011, 01:59 AM
mujjuman mujjuman is offline
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Location: NY
 
Join Date: Feb 2009
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Mein Auto: hoopty
Well whaddyaknow. My coil just failed too... What a coincidence. It's not so bad though, it happened three times and then went away.

Either way it's just one coil and I have to replace it.
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2002 325i, acceleration issue, gas mileage, idle, start up problems


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