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Discussion Starter · #1 ·
Hello everyone, first post here! :hi:

I have a twelve year old 325xi and with what appears to be a common problem - flickering oil pressure light at idle after driving in warm weather. Applying a bit of gas extinguishes it and it only appears in Drive (automatic transmission.) I went to a mechanical who suspected vacuum leak and replaced the intake boot because there was indeed a hole in it. He also used the computer to artificially increase idle RPM's and the problem went away for a while but is now back.:thumbdwn:

I also have P0171 and P0174 codes.

Today I finally went out and bought a mechanical oil pressure gauge since first logical thing seems to be to actually measure the pressure. I got the Bosch FST 8216 but have no idea how to hook it up - I looked around the forums but most threads that revolve around this issue simply mention attaching the gauge where the sender is. I am not sure where the sender is since I've never worked on the car before - I checked realoem but did not find anything related to oil pressure sender :hmm:

Does anyone have a few pictures or a DIY link where it's shown, step by step, how to hook up the gauge temporarily? I am not interested in permanently installing it, just for a bit.

What tools would I need? Also, is this something that the car needs to be lifted for?

Thanks in advance for helping a noob out.
 

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Your oil light is flickering? Or do is there an oil pressure light I don't know about......


That sounds like you have a bad oil level sensor. 40 bucks on Amazon. Also look up your codes.
 

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Discussion Starter · #3 ·
It's the oil pressure light (red.)

I would go ahead on the sensor but want to make sure that the pressure is actually fine first. I've read the the sensor is a common problem but what worries me is that this only happens on warm idle, under which condition the oil would actually be at its least viscosity and low rpm = pump pumping it slowly enough to actually dip below trip level.
 

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:banghead:

OK, first things first.

Oil pressure spec at idle is 7 PSI, so you can see a slight changing in engine idle can likely trigger the oil pressure light to flicker.

I would return the oil pressure gauge and just buy a new oil pressure switch, they often fail and the spring gets weak in them over the years. The oil pressure switch is located on the Oil Filter Housing, but be careful there are 2 sensors that look very similar, one is an oil temperature sensor.

Next you CLEARLY have an engine idle problem with the car that needs to be resolved.

I call BS on the mechanic increasing the engine RPM with a computer, can it be done, yes, should it be done, no. Do most mechanics really know what they are doing, NO.

So lets see, you currently have Lean codes for your engine. Lean codes often cause unstable and often lower than normal idle on these engines. Why not fix your Lean codes, they need to be repaired.

I am going to give you ALL the information you will ever need to sort out your Lean codes. Also keep in mind the power brake booster is likely leaking on your car as well. XI's seem to have more problems with leaking power brake boosters than other cars.

So here you go, fix your Lean codes, which will stabilize the engine idle and it will likely resolve the oil pressure light flickering.

Get an OBDII smart phone/tablet App and interface, typically $30 or less. These Apps are usually best for drivability issues and they support Emission Readiness Monitor Status, Freeze Frame and Live/Realtime data. They are also great for Logging data for review after the car has been driven and can really help find unusual problems.

Android - Touch Scan for $5.00 and ELM327 OBDII to Bluetooth interface.

iProduct - OBD Fusion for $9.99 and ELM327 OBDII to Wifi interface.

Some people prefer to have an extension cable to keep the interface away from their feet.

Something like these cables are often of interested:

http://www.amazon.com/gp/product/B0...ue&ref_=ox_sc_act_title_1&smid=A13I33IUTGJ9BK

http://www.amazon.com/OBDII-Extensi...sbs_263_5?ie=UTF8&refRID=1D2JWFQ9HPSGWZ2SB34Q

I usually suggest getting the OBDII interfaces from Amazon if you are located in the US/North America. Make sure you choose an interface that indicates that the order will be "Fulfilled by Amazon" otherwise you may be waiting for WEEKS for an interface to arrive from Asia. Ebay is another option, but pay attention where the interface will be shipped from, again weeks for an interface from Asia, so if you can wait and want to try to save some money, go for it, but if you need an interface soon, choose wisely.

Read the 2 links below:

http://forum.e46fanatics.com/showthread.php?t=897616

http://forum.e46fanatics.com/showthread.php?t=929501

Need to see Freeze Frame info if the SES/CEL/MIL is on and Fuel Trim values at both warm idle and a steady highway cruise between 45-60 MPH.

MAF issues, first cleaning a MAF RARELY resolves anything, the only thing it usually cleans is your wallet.

If you have recently replaced the MAF, put the original back on the engine until you sort out all of the obvious issues. There are MANY counterfeit MAF's on the market and the major trap is ASSUMING the MAF is not the problem since it was recently replaced. Also quite often the MAF is NOT the cause of idle related Lean conditions and misfires, faulty MAF's usually under report the airflow as a percentage and are more of a problem at highway cruise speeds and not engine idle.

Unplugging the MAF will often cause the engine idle to be smoother, reduce or eliminate idle misfires. This DOES not mean the MAF is bad, it is due to the DME going into a fixed fuel Map mode that is typically by default Richer than when the MAF is connected and this will mask Lean conditions caused by intake and/or crankcase air leaks.

P0102 means for some reason there is not likely a signal from the MAF. Verify if the MAF connector is properly plugged in, sometimes the female terminals in the connector are spread and loose on the MAF pins, sometimes there are broken wires inside the wiring harness between the MAF and the wiring box near the throttle body and sometimes the MAF just is bad with no output signal.

WARNING - DO NOT buy a cheap ebay MAF, there are many Asian counterfeits on the market that do not work properly. See of there is an MAF reading in Grams/Sec. Most E46 have an idle MAF reading of between 3.5-4

Note, there may or may not be Lean Codes showing up. Lean Codes usually trigger at around 10% Fuel Trim values or higher. Keep in mind that sometimes these engines can have a Lean condition that does not or only intermittently triggers Lean Codes. This is why monitoring the Fuel Trims in real time is important. Ideal Fuel Trim values are typically in the 0% to +2.5/+3.0% range.

Read this thread - http://forum.e46fanatics.com/showthread.php?t=1057387

Make ABSOLUTELY sure the O2 sensor wiring has not been mixed up, read these links:

http://forum.e46fanatics.com/showpost.php?p=16249570&postcount=27

http://forum.e46fanatics.com/showpost.php?p=16378620&postcount=26

Read my "BMW 20 Questions" comments in this thread - http://forum.e46fanatics.com/showthread.php?t=1059972

Check for or be aware of cracked valve covers and bad valve cover gaskets:

http://forum.e46fanatics.com/showthread.php?t=1021219

http://forum.e46fanatics.com/showthread.php?t=1053359&page=2&highlight=

http://forum.e46fanatics.com/showthread.php?t=1053359

This information ASSUMES that spark plugs have been checked/replaced. If they have not been inspected, you also need to check for oil filled spark plug wells due to a leaking/cracked valve cover gasket.

http://forum.e46fanatics.com/showpost.php?p=16627742&postcount=11

Search YouTube for Scotty Smoke Test. Do what Scotty does or build a tester from related video. Remove the oil fill cap and make sure the crankcase fills up with smoke, put the oil fill cap back on and check for leaks around the valve cover, oil fill cap, dipstick tube and CCV hoses. Cracked valve covers are pretty common on the E46 as it ages.

Note that the Scotty Smoke Test method is not so good for smaller air/vacuum leaks or fully filling the engine crankcase, for this you really need a smoke machine that can provide a solid and continuous low pressure smoke stream. So plan on building a smoke tester of you thing you will use if more than once or may have smaller and harder to find leaks.
 

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Discussion Starter · #5 · (Edited)
jfoj,

Thanks for the detailed reply. I've skimmed your threads before but will pay more attention now. One thing (regarding DISA) - is there a way to check if the DISA Is bad before actually removing it? I saw that one youtube video where the guy had terrible rattling coming from the engine when running so he unplugged the DISA connector and the rattling went away. Is this reliable? I did it as well and heard no difference.
 

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DISA check needs to be removed and at a minimum, resealed. Depending on how the car is driven, most DISA's need to be rebuilt or replaced by year 8-10. You should just resign yourself that everything needs to be addressed on your car.
 
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