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Steve, BMW Expert
Category: BMW
Satisfied Customers: 22846
Experience:  BMW Expert
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Am reading these codes on a 2002 325xi,

Customer Question

Am reading these codes on a 2002 325xi, P01704,p01083,p0185,p0171, I changed all the sensor and tune it up run fine but sercive engine. Light come on.
JA: Do you have the trouble code? Do you have a code reader or scan tool?
Customer: No I went to auto zone.
JA: I'll pass this info along to the BMW Mechanic so that he can get you a quick fix. Are you fixing your 325xi yourself? What have you tried so far?
Customer: Every thing changed all four sensor and tune up changed everything from coil to spark , air filter too.
JA: Anything else you want the mechanic to know before I connect you?
Customer: No please connect
Submitted: 26 days ago.
Category: BMW
Expert:  Steve replied 26 days ago.
What exactly has been changed? O2 sensors and plugs and coils? Anything else? Any other checks made?
Customer: replied 26 days ago.
Change all above that it.
Customer: replied 26 days ago.
What might be wrong
Expert:  Steve replied 26 days ago.

will provide an honest answer. I trust this will be appreciated. Please remember that a low rating PUNISHES me for being honest and that I receive nothing for my time until a positive rating is clicked.
Thank you for your attention to the rating requirement.

this is a lean running condition, not an o2 sensor issue or plugs/coils.

This would most likely be caused by an unmetered intake air leak of some kind.

Unmetered air leaks allow excess air into the engine and cause the fuel/air mixture to go out of alignment.

The definitive test for intake leaks is a smoke test where a smoke machine (kind of similar to a fog machine you would see at a concert or on Halloween) pumps the intake full of smoke and then the smoke reveals the leaks as it seeps out through any cracks or holes.

However, you can still check for leaks at home. To check for intake leaks, visually inspect the intake area for any cracked hoses/pipes. If you can't see anything, you can try this trick: spray a can of carb cleaner around the intake with the engine idling. If the idle changes, this indicates that the cleaner is entering the engine and you have localized the area of the leak. You can then inspect further.

The most common source of air leaks is from the rubber intake tubes between the air box, and the throttle.

Another common issue that causes this problem is a failed crankcase vent valve (aka PCV). This valve regulates a vacuum on the crankcase, when they fail, a high vacuum is put on the crankcase - giving an air leak. You can check for this by removing the oil filler cap with the engine running, if there is a high vacuum holding the cap down, the engine stalls, or idle dips a lot, then this valve has failed and is your problem.

the other possible causes are low fuel pressure or a bad airflow sensor, but chances are it is an air leak or bad crankcase vent valve.

Please let me know if you have further questions. Please do not forget to click a positive rating as this is the only way I receive credit for my answer, thank you

Expert:  Steve replied 26 days ago.
if there are no additional questions please kindly CLICK ON a positive rating as this is the only way I receive credit for my time and answer. thank you.

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