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I have a 2008 328i SULEV. Recently the service engine soon (yellow) light came on the dash. With it came a rough idle (idles at 600rpm). I replaced all spark plugs today. She runs and accelerates fine but at certain speeds will make an engine rumble and still idles rough.

Battery needs to be replaced but aside from that, oil & coolant levels are normal. She's got just over 81k. Going to plug in my scanner tomorrow but hoping someone might have an idea what's going on? Thanks
 

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Bad coil can cause engine roughness. But so can an air leak which results in a lean running engine particularly noticeable for a difficult to idle engine which it is first running while 'cold'.
 

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Bad coil can cause engine roughness. But so can an air leak which results in a lean running engine particularly noticeable for a difficult to idle engine which it is first running while 'cold'.
She idles fine; it's rough though like the engine is misfiring or something. I figured the service engine soon light paired with the rumble meant to change spark plugs....
 

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Can a weak battery cause the SES light to appear/ cause a rough idle? My OBD2 scanner is new but a pos. Wouldn't connect so I'm playing the guessing game. She needs a new battery and wiper fluid.
 

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I have the same problem in my 2013 E9c with only 56,000 miles. Had a friend with a basic scanner hook it in and it read misfire. Smoothes out a little at 60-70 MPH but rough idle and stumbles upon acceleration. Thinking of changing plugs and coils. It is a CPO with time still left but hate to pay a big diagnostic fee and dealer costs for plugs and coils.

Any more suggestions?

Bob
 

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...2008 328i SULEV. Recently the service engine soon (yellow) light came on the dash. With it came a rough idle (idles at 600rpm). I replaced all spark plugs today. She runs and accelerates fine but at certain speeds will make an engine rumble and still idles rough...Going to plug in my scanner tomorrow but hoping someone might have an idea what's going on? Thanks
Can a weak battery cause the SES light to appear/ cause a rough idle? My OBD2 scanner is new but a pos. Wouldn't connect so I'm playing the guessing game. She needs a new battery and wiper fluid.
The SES light indicates a Fault Code has been saved in the DME (Engine Control Module), and has NOTHING to do with battery voltage. As has been suggested, you need to determine what Fault Code(s) are saved in the DME, and any scan tool, even a cheap generic P-code reader is capable of doing that (if it works ;-). So before you spend any money on anything new, let's try to figure out WHY your scan tool is NOT working.

QUESTIONS:

1) What is the make & model of your scan tool?
2) When you connect it to the OBD II socket, does the tool power-up, screen light, etc.?
3) If the tool powers-up, the next step is to try to connect to the DME. What protocol have you selected, or have you selected "auto" to have the tool determine the correct protocol?
4) Do you have a Multimeter? (If NOT why not -- $6 from HFT ;-)

If the tool does NOT power-up, check for 12V+ at pin #16 of the OBD II socket (top pin of INBOARD column of pins) with ignition on. Here are the TIS wiring diagrams for the OBD II Socket and also the power supply to pin #16 via fuse F74:
https://www.newtis.info/tisv2/a/en/...tors/connectors-from-x1/x19527-x19527/vetg6Zt
https://www.newtis.info/tisv2/a/en/...onnectors/components/f-fuses/f74-fuse/iRAwk7N

If the tool powers-up, but can't connect, check any manual that came with the tool to determine the procedure for connecting or selecting "auto-connect" mode to determine the correct protocol (think language) used by your vehicle.

Let us know exactly what happens, carefully noting each step, and we can determine where the wheels come off. :)

George
 

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Discussion Starter #8
...2008 328i SULEV. Recently the service engine soon (yellow) light came on the dash. With it came a rough idle (idles at 600rpm). I replaced all spark plugs today. She runs and accelerates fine but at certain speeds will make an engine rumble and still idles rough...Going to plug in my scanner tomorrow but hoping someone might have an idea what's going on? Thanks
Can a weak battery cause the SES light to appear/ cause a rough idle? My OBD2 scanner is new but a pos. Wouldn't connect so I'm playing the guessing game. She needs a new battery and wiper fluid.
The SES light indicates a Fault Code has been saved in the DME (Engine Control Module), and has NOTHING to do with battery voltage. As has been suggested, you need to determine what Fault Code(s) are saved in the DME, and any scan tool, even a cheap generic P-code reader is capable of doing that (if it works ***x1f609;. So before you spend any money on anything new, let's try to figure out WHY your scan tool is NOT working.

QUESTIONS:

1) What is the make & model of your scan tool?
2) When you connect it to the OBD II socket, does the tool power-up, screen light, etc.?
3) If the tool powers-up, the next step is to try to connect to the DME. What protocol have you selected, or have you selected "auto" to have the tool determine the correct protocol?
4) Do you have a Multimeter? (If NOT why not -- $6 from HFT ***x1f609;

If the tool does NOT power-up, check for 12V+ at pin #16 of the OBD II socket (top pin of INBOARD column of pins) with ignition on. Here are the TIS wiring diagrams for the OBD II Socket and also the power supply to pin #16 via fuse F74:
https://www.newtis.info/tisv2/a/en/...tors/connectors-from-x1/x19527-x19527/vetg6Zt
https://www.newtis.info/tisv2/a/en/...onnectors/components/f-fuses/f74-fuse/iRAwk7N

If the tool powers-up, but can't connect, check any manual that came with the tool to determine the procedure for connecting or selecting "auto-connect" mode to determine the correct protocol (think language) used by your vehicle.

Let us know exactly what happens, carefully noting each step, and we can determine where the wheels come off. <img src="http://s1.bimmerfest.com/forums/images/smilies/smile3453453.gif" border="0" alt="" title="Smilie" class="inlineimg" />

George
Good looks, George. It's an OBD2 Kobra scanner. I connect it to the onboard computer and only the first two lights are lit (red). When I select "connect" on the android app, it comes back with an error. I've restarted the phone, unplugged the scanner, uninstalled the app, etc.

Anyone know a trick to this?


Thanks
 

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Discussion Starter #9
Ok so I downloaded another OBD2 app and on my tablet this time. Error code P0306 - cylinder 6 misfire. Will update the thread once I replace the coil pack.

Cheers
 

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Ok so I downloaded another OBD2 app and on my tablet this time. Error code P0306 - cylinder 6 misfire. Will update the thread once I replace the coil pack.

Cheers
check which coils you have, if they dont have a silver sleeve over them then replace them all. they updated the bosch coils to delphi and theres an SI_B to replace all coils and plugs. if your in a SULEV state bmw warrenty will cover both plugs nd coils as long as your under 15 years 150k miles.
 

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Ok so I downloaded another OBD2 app and on my tablet this time. Error code P0306 - cylinder 6 misfire. Will update the thread once I replace the coil pack.
I would CLEAR the P0306 and then swap plug AND coil between cylinders 5 & 6, and see if fault follows the coil & plug (or you could even switch plugs between 6 & 4, so you KNOW what part it follows if you now get P0305 or P0304. If P0306 returns with different coil & plug, then you either have:
1) a wiring/connector issue on #6 cylinder coil, OR
2) an injector issue on cylinder #6.

May seem like extra work, but the idea is to identify the CAUSE of cylinder #6 "misfire" BEFORE you throw parts at it. Just think where you might be IF you had done this BEFORE changing plugs. :)

Remember in the N51/N52, a "misfire' is NOT an electrical test of spark/ignition, but RATHER a measurement of RPM decrease on the power stroke of cylinder #6 (in this case) as compared to the RPM during power stroke of cylinder immediately BEFORE #6 and immediately AFTER #6 in the firing order, and this measurement is done by the Crankshaft Position Sensor which accurately signals crankshaft RPM to the DME which makes the computation and determines which cylinder "goes slow." So in your case, SOMETHING is causing less power on the power stroke of cylinder 6 than is generated by cylinders #3 and #2.

Even if you have an N51 that has plugs & coils covered under extended warranty, doing diagnostics yourself is likely to save time & aggravation.

Please let us know what you find,
George
 
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