[speedwheels]

Folks,
I spent a good hour searching through the forums on what my symptoms could mean (search yielded coils, vacuum leak and/or plugs) so I have not been lazy before I posted this. I was hoping to get some feedback on what my car symptoms could be.

I have a 2007 BMW N54 335i Sedan with 115k miles on it. About a couple of months ago, my car began having a rough misfiring idle (like it was going to stall) when I started my car. I am pretty sure the rough idle happens everytime I start my car after it has sitting for 3-4 hours. Engine might still be pretty warm in 3-4 hours so I dont know if this is classified as a cold-start condition but those are the parameters under which this occurs. If I give it a little gas (rev past 2k rpm), the engine completely smooths out and once I get driving the rough idle/misfire goes away completely. Power on the highway is normal and after the car has been running for a few minutes, I can idle the car just fine. The problem happens only during start.

Another thing to note: NO Check Engine light.

My plugs were replaced last year and have less than 10k miles on them so I am reasonably confident the issue is not with my spark plugs especially because the misfire does not happen under load.

There is no hesitation during the actual starting of the car (it fires right up to a rough idle) so I am tending to think this is not a HPFP issue. My HPFP was last replaced 2 years ago with the latest BMW part number.

Right now I am thinking clogged/bad injectors(i did run the car to nearly empty on the fuel tank once) or coils (not been replaced for a few years) or perhaps my battery. My battery is on it's last legs and it is possible it is losing charge in the few hours the car sits before I start it and once the car gets going the alternator is able to power the coils (this is a wild guess as I am not sure how effective the alternator is at idle speeds).

I have not pulled codes using a BMW reader, although I did buy an INPA USB-OBD2 cable. The software setup seems very time consuming just to read diagnostic codes (i don't ever plan to code the car).


Does anyone have suggestions on what it could be. I know eventually I will have to take it to someone in the baltimore area to get it scanned but I am trying to have a reasonable understanding of the problem.

Thanks for reading this lengthy post.

[vb7200]

I've also been experiencing rough starting. I'm thinking it's because of a fuel leak. I've noticed when it's sitting, if I don't let the pumps prime the lines, It will long crank/idle rough when it starts. I've gotten myself into the habit of locking/unlocking the car as I'm walking to it to let the pumps run a little bit, and then it starts fine.

[Sgop335]

Originally Posted by kchilaka

Folks,
I spent a good hour searching through the forums on what my symptoms could mean (search yielded coils, vacuum leak and/or plugs) so I have not been lazy before I posted this. I was hoping to get some feedback on what my car symptoms could be.

I have a 2007 BMW N54 335i Sedan with 115k miles on it. About a couple of months ago, my car began having a rough misfiring idle (like it was going to stall) when I started my car. I am pretty sure the rough idle happens everytime I start my car after it has sitting for 3-4 hours. Engine might still be pretty warm in 3-4 hours so I dont know if this is classified as a cold-start condition but those are the parameters under which this occurs. If I give it a little gas (rev past 2k rpm), the engine completely smooths out and once I get driving the rough idle/misfire goes away completely. Power on the highway is normal and after the car has been running for a few minutes, I can idle the car just fine. The problem happens only during start.

Another thing to note: NO Check Engine light.

My plugs were replaced last year and have less than 10k miles on them so I am reasonably confident the issue is not with my spark plugs especially because the misfire does not happen under load.

There is no hesitation during the actual starting of the car (it fires right up to a rough idle) so I am tending to think this is not a HPFP issue. My HPFP was last replaced 2 years ago with the latest BMW part number.

Right now I am thinking clogged/bad injectors(i did run the car to nearly empty on the fuel tank once) or coils (not been replaced for a few years) or perhaps my battery. My battery is on it's last legs and it is possible it is losing charge in the few hours the car sits before I start it and once the car gets going the alternator is able to power the coils (this is a wild guess as I am not sure how effective the alternator is at idle speeds).

I have not pulled codes using a BMW reader, although I did buy an INPA USB-OBD2 cable. The software setup seems very time consuming just to read diagnostic codes (i don't ever plan to code the car).


Does anyone have suggestions on what it could be. I know eventually I will have to take it to someone in the baltimore area to get it scanned but I am trying to have a reasonable understanding of the problem.

Thanks for reading this lengthy post.

Free mhd app would be quite suitable and very easy to read codes, uses the cable but needs usb to micr usb adapter.

[speedwheels]

Originally Posted by Sgop335

Free mhd app would be quite suitable and very easy to read codes, uses the cable but needs usb to micr usb adapter.

Oh. Didn't know about the MHD app. I assume the free version can read codes. I happen to have an OTG cable. Will try it out. Thanks !

[speedwheels]

Originally Posted by vb7200

I've also been experiencing rough starting. I'm thinking it's because of a fuel leak. I've noticed when it's sitting, if I don't let the pumps prime the lines, It will long crank/idle rough when it starts. I've gotten myself into the habit of locking/unlocking the car as I'm walking to it to let the pumps run a little bit, and then it starts fine.

This is a different problem than what I am having. My car fires right up, it just hiccups after starting. The symptoms you describe (long crank plus rough idle) are the ones I had when my HPFP went out.. You might want to scan as well..

[makethiscardriveable]

Reviving some old stuff here but I have almost the same rough idle issues. Vacuum lines done, Index 12 injectors, hpfp replaced, spark plugs and coils done. Not sure what else to do

[tisdrew]

It's not coil packs. If it were, you would get hesitation during WOT and higher rpms.

[beetle6986]

Originally Posted by makethiscardriveable

Reviving some old stuff here but I have almost the same rough idle issues. Vacuum lines done, Index 12 injectors, hpfp replaced, spark plugs and coils done. Not sure what else to do

My car does this also. I've done all the same things you did in addition to cleaning the intake valves. It only seems to do it when the car is first started. Mostly the first 30 seconds while the car is running rich. Although, I'm not too worried about it. The car runs great once it's warm.

[wrongmark]

Sounds like I have a similar if not the same issue (albeit different engine n43 2.0i). Car starts up easily, then runs a bit rough at idle. It runs very rough and lumpy for the first 5 mins of driving then runs and idles totally fine. Don't want to hijack your thread but would be great to know if you solve it.

[Jaronbwall]

Have any of you guys walnut blasted the intake? It sounds very similar to clogged intake ports. When it gets bad the idle is affected big time.

[dpaul]

Sure, could be you need a walnut blast but in my experience, idle issues related to carbon buildup at the intake ports don't go away after 5 minutes of running.

Why don't you log/monitor during startup and initial running? I'd suggest looking at VANOS values actual versus commanded but of course, there could be many explanations for this issue.

[cmh269]

Hoping to revive this thread. I'm having very similar symptoms on my 08 535. I'm really suspecting something to do with the VANOS or possibly O2 sensors for a couple reasons:
1) Problem disappears once oil temp has warmed up.
2) The misfire is so inconsistent. When first starting engine idles at around 1200rpm...no problem. Gradually makes its way down to about 700....no problem. Then for the final drop down to 600rpm, you actually feel a very noticeable shudder and BAM, rough idle at around 600-650rpm. This eventually settles down as the car warms up. If I wait 5 mins (more in the Canadian winter) before driving everything is normal. If I try to drive right away, I feel a loss of power and a lot of studdering, fluttering feel to the engine. The AFR seems ok, so I'm suspecting something to do with VANOS....

Any thoughts?

[Saif2018]

Originally Posted by cmh269

Hoping to revive this thread. I'm having very similar symptoms on my 08 535. I'm really suspecting something to do with the VANOS or possibly O2 sensors for a couple reasons:
1) Problem disappears once oil temp has warmed up.
2) The misfire is so inconsistent. When first starting engine idles at around 1200rpm...no problem. Gradually makes its way down to about 700....no problem. Then for the final drop down to 600rpm, you actually feel a very noticeable shudder and BAM, rough idle at around 600-650rpm. This eventually settles down as the car warms up. If I wait 5 mins (more in the Canadian winter) before driving everything is normal. If I try to drive right away, I feel a loss of power and a lot of studdering, fluttering feel to the engine. The AFR seems ok, so I'm suspecting something to do with VANOS....

Any thoughts?

Assuming you have MHD

Try adjusting Idle rpm to 700 or 750rpm

I've set mine (335i) to 750rpm and it's smooth as butter at idle.

[iqraceworks]

For all you guys having right idling issues after startup.....you have checked for leaky injector(s) right? Very common issue that causes rough idleing right after startup.

Fuel leaks out of the injector as the motor sits for a while...runs right down to the tip of the sparkplug. It takes a while to burn that excess fuel off of the plug right after startup...so you get rough idleing and/or misfires.

It's easy to check for leaking injectors. Pull the spark plugs out in the morning before you start the car for the first time. If any are wet or even smell like fuel, that cylinder has a leaky injector. Replace it.

[virtual_law]

Originally Posted by speedwheels

Folks,
I spent a good hour searching through the forums on what my symptoms could mean (search yielded coils, vacuum leak and/or plugs) so I have not been lazy before I posted this. I was hoping to get some feedback on what my car symptoms could be.

I have a 2007 BMW N54 335i Sedan with 115k miles on it. About a couple of months ago, my car began having a rough misfiring idle (like it was going to stall) when I started my car. I am pretty sure the rough idle happens everytime I start my car after it has sitting for 3-4 hours. Engine might still be pretty warm in 3-4 hours so I dont know if this is classified as a cold-start condition but those are the parameters under which this occurs. If I give it a little gas (rev past 2k rpm), the engine completely smooths out and once I get driving the rough idle/misfire goes away completely. Power on the highway is normal and after the car has been running for a few minutes, I can idle the car just fine. The problem happens only during start.

Another thing to note: NO Check Engine light.

My plugs were replaced last year and have less than 10k miles on them so I am reasonably confident the issue is not with my spark plugs especially because the misfire does not happen under load.

There is no hesitation during the actual starting of the car (it fires right up to a rough idle) so I am tending to think this is not a HPFP issue. My HPFP was last replaced 2 years ago with the latest BMW part number.

Right now I am thinking clogged/bad injectors(i did run the car to nearly empty on the fuel tank once) or coils (not been replaced for a few years) or perhaps my battery. My battery is on it's last legs and it is possible it is losing charge in the few hours the car sits before I start it and once the car gets going the alternator is able to power the coils (this is a wild guess as I am not sure how effective the alternator is at idle speeds).

I have not pulled codes using a BMW reader, although I did buy an INPA USB-OBD2 cable. The software setup seems very time consuming just to read diagnostic codes (i don't ever plan to code the car).


Does anyone have suggestions on what it could be. I know eventually I will have to take it to someone in the baltimore area to get it scanned but I am trying to have a reasonable understanding of the problem.

Thanks for reading this lengthy post.

Have an '07 335i too with the exact same issue. Did anyone pinpoint a solution for this?

[Klos]

Originally Posted by cmh269

Hoping to revive this thread. I'm having very similar symptoms on my 08 535. I'm really suspecting something to do with the VANOS or possibly O2 sensors for a couple reasons:
1) Problem disappears once oil temp has warmed up.
2) The misfire is so inconsistent. When first starting engine idles at around 1200rpm...no problem. Gradually makes its way down to about 700....no problem. Then for the final drop down to 600rpm, you actually feel a very noticeable shudder and BAM, rough idle at around 600-650rpm. This eventually settles down as the car warms up. If I wait 5 mins (more in the Canadian winter) before driving everything is normal. If I try to drive right away, I feel a loss of power and a lot of studdering, fluttering feel to the engine. The AFR seems ok, so I'm suspecting something to do with VANOS....

Any thoughts?

Have you figured out the problem yet, mine is exactly the same

[AZM40i]

Originally Posted by makethiscardriveable

Reviving some old stuff here but I have almost the same rough idle issues. Vacuum lines done, Index 12 injectors, hpfp replaced, spark plugs and coils done. Not sure what else to do

I was in the same boat except the hpfp. I had a rough idle with random misses. Replaced valve cover housing as the gasket was rolled. Replaced coils and plugs. Installed new to me injectors with lower miles and no previous issues. Still had rough idle. Stutters idle. You could tell it was missing in idle but it was hard to mark it happen under load. Sixth gear. Floored to the resistance point. Still no miss. So finally me and my buddy started switching stuff from his car to mine. He has a n54 with no missing. Threw his Ngk step colder from a n20 in and the problem went away. Idle is smooth and no misses. BMW part # 12-12-0-039-6641002D $105 for 6. You should try it.

[ISI236]

I’m currently having the same issues not sure what the problem acctually is but I’ve ordered a set of index 12s mainly because they were on sale but I’m sure its the injectors I don think the injectors are leaking too severely but I have similar symptoms as the above cold start rough idle then it settled and the car drives almost perfectly no CEL.

On another note i think my wastegates are failing which is causing the rough idle but again no conclusive evidence so the turbos are being replaced with 19t’s.

Don’t judge the Chinese turbos I’m a broke uni student from the UK so can’t really afford a single turbo setup.

Overall I’m kind of stuck as the cars a daily driver but I signed up for the n54 problems when I bought it so not gonna whine about it.

2 questions:

The injectors are taking a while to come but I was wondering whether it’s still drive able in the meantime? I need it for short trips maybe 10-30 mins of driving

When the 19t turbos are installed will an MHD tune be sufficient? If so which map? as I’m not aiming for huge HP numbers just to make the car driveable until I can save again for an intercooler, fuel pump, and maybe cat less down pipes?

P.S the car is bone stock other than a Cat back exhaust I know I’m doing the mods in a wierd order but I’m going by what fails first so hope that helps