[mynameisname]

Hey all,

I've recently been getting rough idle when cold starting and engine misfires when going over 3k rpm. Car has 107k miles. It's a n26 motor. I first installed a JB4 and later an ER catted downpipe with no issues. For about a month I took off the JB4 and the car threw codes for catalyst and o2 sensor which would sometimes clear by themselves. I flashed bootmod3 and cleared codes and the car ran fine without any issues. About another 3 weeks later I started getting misfires (engine jerks) at WOT without any codes. From this point I started getting rough idles when starting the car in the mornings, it's gotten rougher as the days go by. I changed spark plugs, ignition coils, engine oil, and engine air filter. No improvements noticed. Now when I go above 3k rpm a little quickly I get misfires and CEL comes on with the drivetrain malfunction and the car basically goes into limp mode with huge loss of power and really shaky ride. Once I stop and turn off the engine and turn it back on the lights sometimes clear and it's no longer in limp mode or the CEL stays and is no longer in limp mode. These are the codes I see with the BM3 software.





Any suggestions?

I'm thinking the next thing is to clean the VANOS solenoids. If that doesn't work, then replacing o2 sensors. Not sure where else to go from there. I'm out of warranty so I'd prefer not to take it to BMW

[RMachuca3d]

Nothing to lose by trying to clean the MAF, some ppl had rough idles and after cleaning it was back to normal.

[fiveohwblow]

I would begin looking into injector malfunction.

[mynameisname]

RMachuca3d fiveohwblow will try both this weekend and update. Thanks!

[rjd_F30]

Cleaning the MAF isn't a bad idea, can't hurt to give that a shot, but it sounds like it's missing or leaning out really bad. Have you tried flashing back to stock to see if the issue persists?

[take1step]

First check and replace spark plugs if necessary. Make sure they're gapped properly.

Then I would look into injectors.

[mynameisname]

rjdnyy224 yeah I'm flashed back to stock currently but same issues persist.
take1step I've replaced plugs and coils, but haven't done injectors yet so that's what I'll be doing this weekend.

[rjd_F30]

Originally Posted by mynameisname

rjdnyy224 yeah I'm flashed back to stock currently but same issues persist.
take1step I've replaced plugs and coils, but haven't done injectors yet so that's what I'll be doing this weekend.

Gotcha, so definitely a mechanical issue. Could be injectors/HPFP too, or something along the fuel path. Interested to see what whoever you take it to for the second opinion says.

[mynameisname]

Late Update: it was fixed with spark plugs gapped properly and using 1 step colder plugs. Engine still shudders every now and then when cold starting and not fully at operational temp but nothing serious. CEL went away after I replaced the upstream O2 sensor for bank 1 sensor 1.

[jubiso]

I have very similar misfire issues with my car. I am posting this so that the forum admin allows me to start a new thread. I am new to this forum.

[Luverse]

hope your engine is not damaged

but, here's a story of mine, with blown N20 engine, with similar symptoms with you

https://f30.bimmerpost.com/forums/sh...&postcount=737

https://f30.bimmerpost.com/forums/sh...&postcount=751

https://f30.bimmerpost.com/forums/sh...&postcount=777

i sold the car afterward, and now driving a B48 330i FBO with BM3 and no issue

[jan31]

Originally Posted by mynameisname

Late Update: it was fixed with spark plugs gapped properly and using 1 step colder plugs. Engine still shudders every now and then when cold starting and not fully at operational temp but nothing serious. CEL went away after I replaced the upstream O2 sensor for bank 1 sensor 1.

Originally Posted by mynameisname

Late Update: it was fixed with spark plugs gapped properly and using 1 step colder plugs. Engine still shudders every now and then when cold starting and not fully at operational temp but nothing serious. CEL went away after I replaced the upstream O2 sensor for bank 1 sensor 1.

Which plugs you used and how much gap?

[mike@x-ph.com]

Originally Posted by mynameisname

Late Update: it was fixed with spark plugs gapped properly and using 1 step colder plugs. Engine still shudders every now and then when cold starting and not fully at operational temp but nothing serious. CEL went away after I replaced the upstream O2 sensor for bank 1 sensor 1.

[jan31]

Originally Posted by mike@x-ph.com

Can I do stage 1 with stock charge pipe? Will hold?

[Luverse]

Originally Posted by jan31

Can I do stage 1 with stock charge pipe? Will hold?

yes it will
stage 2 with stock CP will hold as well, but for how long and is it worth the risk?

[mike@x-ph.com]

Originally Posted by jan31

Can I do stage 1 with stock charge pipe? Will hold?

I recommend upgrading the charge pipe when car is tuned no matter what stage you run

[jan31]

Originally Posted by mike@x-ph.com

I recommend upgrading the charge pipe when car is tuned no matter what stage you run

Thanks for the info!

[GreenF30N26]

I’ve heard no reports of anyone blowing either charge pipe on an N20/26 whether stock, stage 1 or stage 2. Some of the fastest N20s on the quarter mile thread are running stock pipes.

[jan31]

Originally Posted by Green33

I’ve heard no reports of anyone blowing either charge pipe on an N20/26 whether stock, stage 1 or stage 2. Some of the fastest N20s on the quarter mile thread are running stock pipes.

Good