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General E46 Forum
This is the place to get answers, opinions and everything you need related to your E46 (sedan, coupe, convertible and wagon) BMW!

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Old 07-22-2015, 03:40 AM   #1
Registered User
Join Date: Mar 2015
Posts: 8
318i cold startup problem

This issue only persists on cold startups only. I got a E46 318i and it's got 175000km's on it.
The problem:
On ever cold startup, the car drives like a snail, I cannot drive beyond 2500rpm on any gear and the rpm fluctuates. The car idles fine and everything returns to normal 5 minutes after startup.

I have changed the plugs and with the MAF sensor disconnected, there seems to be no problem, even on cold startups. Well sometimes the engine shuts down with the MAF disconnected. The acceleration seems to improve tremendously without the MAF sensor.

Should I get a new MAF sensor? Has anyone had similar problem and came up with a solution? Click image for larger version

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Old 07-22-2015, 06:56 AM   #2
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Join Date: Nov 2009
Location: Fairfax, VA USA
Posts: 22,993
My Ride: 330CiC, M5, X5, E93
Not likely the MAF sensor.

We do not have many 318 here in the US, but the problems we have with the I6 are pretty much the same. Not 100% sure how each system is set up on your engine, you will need to do some more research and compare what may be similar on your engine.

Most cold start problems are typically vacuum leaks.

Suggest you read this information below. Not sure your car fully supported EOBD, but if it does, get an OBDII App.

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 $3.95 and ELM327 OBDII to Bluetooth interface.

iProduct - OBD Fusion for $9.95 and ELM327 OBDII to Wifi interface.

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:



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:



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:




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.


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.
Solve your misfires, lean codes, rough idle - http://forum.e46fanatics.com/showthread.php?t=897616

Fuel pump failures - http://forum.e46fanatics.com/showthread.php?t=929501

Temp Info - http://forum.e46fanatics.com/showthread.php?t=964491

Hidden OBC Menu - Check Voltage, Temp, Fuel Level - http://forum.e46fanatics.com/showthread.php?t=239619

E46/E39 GM5 Door Lock Info - www.bmwgm5.com

Lower hose temp switch O-ring - BMW #13621743299
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Old 07-22-2015, 08:25 AM   #3
Registered User
Join Date: Dec 2010
Location: libya
Posts: 19
My Ride: bmw318i
first...your car any model?...98...or 2002...because 318 1998 is not as 2002...
and i have one 318 2002 and was with me as this problem ...it is in camshaft sensor...
..when i washing my engine car ..there are some water inside in camshaft sensor....
sorry my dear my english is very bad...iam still learning english....
my greetings
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Old 07-27-2015, 01:39 AM   #4
Registered User
Join Date: Mar 2015
Posts: 8
Problem solved, it was the MAF sensor that was playing up.
Car info: year 2000 E46 318i with 178000kms on the clock.
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