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1999 e39 528i 2001 e46 325i
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Discussion Starter #1
Hi! I own an e46 325i 2001 with basically stock internals minus a cold air intake. I'm in NYS and have had a lot of trouble getting my car inspected. This is my first car and I've had it for about 10 months now. I've done some work to it (vacuum lines, power steering res replacement, head gasket) and I'm about to do an oil housing gasket replacement, a trunk floor right replacement (old one rusted out), new brakes and rotors. I have been having some rough idle problems (only on cold starts and occasional stops) and I've had to reset my codes often to clear up the stuff random stuff but I think at this point the sensors for my car have gone bad and they won't tell me if I have a "service engine soon" light on. how would I go about changing those sensors out so all the monitors can read on my code reader? I'm currently getting (3) codes that are set off, P1346 (Misfire During Start Cylinder 3) P0135 (02 Sensor Heater Circuit Bank 1 Sensor 1) and P0155 (02 Sensor Heater Circut Bank 2 Sensor 1) is it possible I need to change out my Vanos seals? Its been a struggle and I need it to be fixed finally. Any help is very much appreciated :)

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Hey on the O2 sensor heat circuit codes, check to see if your O2 sensors are plugged in correctly. After a recent head gasket, I was getting both those codes and I discovered I had mistakenly plugged the rear O2 sensor into the front O2 sensor - yeah I know what a dumbass - but the DME wasn't getting a signal from either one as they were plugged into each other. fixed the plugs and error went away.
 

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1999 e39 528i 2001 e46 325i
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Discussion Starter #3
Hey on the O2 sensor heat circuit codes, check to see if your O2 sensors are plugged in correctly. After a recent head gasket, I was getting both those codes and I discovered I had mistakenly plugged the rear O2 sensor into the front O2 sensor - yeah I know what a dumbass - but the DME wasn't getting a signal from either one as they were plugged into each other. fixed the plugs and error went away.
I will definitely be sure to check them to see if they are thank you! were you getting rough idles from that?
 

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no rough idles... just the two O2 heater codes. Your rough idle could be many things, but maybe you check for leaks in the intake boots. You might also try unplugging MAF sensor and see if it smooths the idle. If it does you likely have an intake leak (or a bad MAF- less likely)
 

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1999 e39 528i 2001 e46 325i
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Discussion Starter #5
no rough idles... just the two O2 heater codes. Your rough idle could be many things, but maybe you check for leaks in the intake boots. You might also try unplugging MAF sensor and see if it smooths the idle. If it does you likely have an intake leak (or a bad MAF- less likely)
I feel like it is that too but I haven't gone that far down into the corner of my engine to check it seems whenever i press the gas sometimes (at a standstill) when its dropping RPMs to go back to 700 sometimes it will go lower than 700 and go to like 500 and then it will jump back to 700 and idle there for a little.
 

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2004 325i automagic
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I cant buy cigars at 18 in NYS but I can ask someone older than me to get one thank you so much!
Wow, old enough to vote, otherwise be an adult, and serve in the military, but not old enough to buy cigs ... holy crap ...
 

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1999 e39 528i 2001 e46 325i
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Discussion Starter #12
OP, what is the mileage? Are the sensors original?
The mileage is around 220000 and I'm assuming so. For NYS I need to have ran through at least 5 of my monitors and I'm assuming if those (sensors) that read the actual engine problems are bad it will take forever to get the actual code. I cant ask the previous owners anything they kinda dumped on me with the car but I still love it.
 

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2003 330cic, 2003 325iT
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The mileage is around 220000 and I'm assuming so. For NYS I need to have ran through at least 5 of my monitors and I'm assuming if those (sensors) that read the actual engine problems are bad it will take forever to get the actual code. I cant ask the previous owners anything they kinda dumped on me with the car but I still love it.
Replace the MAF with VDO/Siemens and the pre-cat sensors with Bosch. Don't hesitate. You are way, way past the mileage on O2, and comfortably into senescence with MAF.

Sensors won't affect misfire during start, because they are ignored, but replacing them will eliminate a source of confusion in the system. They are definitely no longer performing.

Clean the IAC (idle control valve) - with carb cleaner. The valve should "clack" without hesitation when you twist the IAC back and forth quickly.

Replace both boots, and every vacuum line, including the SAP solenoid lines in the back if you have them. I would also check or missing caps on the back of the manifold with a mirror. Replace the CVV if original.

Test the fuel pressure (50psi with the ignition on and engine off). If the filter is over 60k, replace it. If it is original, then DEFINITELY replace it. It is a maintenance item like an oil filter.

It is around $680 to do a relatively thorough intake refresh. Happy to send you the part list and the list of tasks if it would help. Otherwise, you will be replacing lots of things one at a time and it gets really old.
 

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1999 e39 528i 2001 e46 325i
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Discussion Starter #15
Replace the MAF with VDO/Siemens and the pre-cat sensors with Bosch. Don't hesitate. You are way, way past the mileage on O2, and comfortably into senescence with MAF.

Sensors won't affect misfire during start, because they are ignored, but replacing them will eliminate a source of confusion in the system. They are definitely no longer performing.

Clean the IAC (idle control valve) - with carb cleaner. The valve should "clack" without hesitation when you twist the IAC back and forth quickly.

Replace both boots, and every vacuum line, including the SAP solenoid lines in the back if you have them. I would also check or missing caps on the back of the manifold with a mirror. Replace the CVV if original.

Test the fuel pressure (50psi with the ignition on and engine off). If the filter is over 60k, replace it. If it is original, then DEFINITELY replace it. It is a maintenance item like an oil filter.

It is around $680 to do a relatively thorough intake refresh. Happy to send you the part list and the list of tasks if it would help. Otherwise, you will be replacing lots of things one at a time and it gets really old.
I would love a part list for that thanks you so much! I know some things were replaced by the previous owners (cause of their sloppy reassembly) but I'm not sure about those parts. Is there a way to check the 02s with a multimeter to be able to tell if it's reached it's potential for use? Those lil parts are kinda expensive so if I'm gonna take those out I'm gonna want to make sure they're dead.
 

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2003 330cic, 2003 325iT
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I would love a part list for that thanks you so much! I know some things were replaced by the previous owners (cause of their sloppy reassembly) but I'm not sure about those parts. Is there a way to check the 02s with a multimeter to be able to tell if it's reached it's potential for use? Those lil parts are kinda expensive so if I'm gonna take those out I'm gonna want to make sure they're dead.
You can test the hall sensors, but you can't really test the O2 sensors easily. If you run a log from a cold start of the O2 sensor values, you can see if they respond late. But seriously, yours are gone.

A few people asked for the parts list, so I made a post - Intake refresh guide

Message me and I can share the original spreadsheet
 

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1999 e39 528i 2001 e46 325i
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Discussion Starter #18
You can test the hall sensors, but you can't really test the O2 sensors easily. If you run a log from a cold start of the O2 sensor values, you can see if they respond late. But seriously, yours are gone.

A few people asked for the parts list, so I made a post - Intake refresh guide

Message me and I can share the
Alright, I will take a look at ordering some bosh o2's thank you and ill check what I can for that intake refresh guide to see if that's the cause of my rough idles.
 

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1999 e39 528i 2001 e46 325i
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Discussion Starter #20
Definitely clean the IAC
I've had that idea for about a month but I'm scared to break something important that's plastic and them having to wait a week for fcp euro to send me my parts:LOL:
 
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