99 528i random misfire running rich - Bimmerfest - BMW Forums



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E39 (1997 - 2003)
The BMW 5-Series (E39 chassis) was introduced in the United States as a 1997 model year car and lasted until the 2004 when the E60 chassis was released. The United States saw several variations including the 525i, 528i, 530i and 540i. -- View the E39 Wiki

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  #1  
Old 09-11-2019, 01:52 PM
Agcmrjazzy Agcmrjazzy is offline
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99 528i random misfire running rich

Hello everybody, I have a 99 528i and a few weeks ago it was runing like I had put racing cams in. I changed plugs, coil boots, and cleaned the maf sensor. Codes read now misfire in 3,5,and 6 and random misfire code. I know what I have done has helped some because before I did all that it was misfire on all cylinders but #2. Now when I cleaned the maf sensor I noticed up by the throttle body a hose going beside it and it was broke off. Don't know if this would cause the misfires I have now or if it is still something else.
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  #2  
Old 09-11-2019, 03:38 PM
Chedley Chedley is offline
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Yes, clean up the throttle body with carb cleaner, replace that broken hose, reset the adaptations.
Then test drive.
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  #3  
Old 09-11-2019, 04:15 PM
Agcmrjazzy Agcmrjazzy is offline
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Reset adaptations meaning what? And the intake is clean. From what I have seen it's the hose going to the idle control valve.
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  #4  
Old 09-11-2019, 05:31 PM
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mattmar1 mattmar1 is offline
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a pic of the broke hose or a better identification of it would help. if its a vacuum hose, this would definitely cause exactly what youre seeing. random misfire codes are often set by a vac leak.
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  #5  
Old 09-11-2019, 06:40 PM
Agcmrjazzy Agcmrjazzy is offline
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This is the intake boot that goes on the throttle body. The small hose is the one that broke off
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  #6  
Old 09-12-2019, 06:07 AM
jbarb jbarb is offline
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Quote:
Originally Posted by mattmar1 View Post
if its a vacuum hose, this would definitely cause exactly what youre seeing. random misfire codes are often set by a vac leak.
This ^

Like others have suggested you might as well clean the throttle body and ICV when your in that under-hood neighborhood too.
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  #7  
Old 09-12-2019, 01:43 PM
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mattmar1 mattmar1 is offline
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oh yes one heckuva vac leak there. unsure...was it replaced? basically, the MAF tracks the amount of air allowed in to the engine for combustion. you have a post MAF air leak with that portion of the boot broken. youre confusing the system, and the 02's are trying to compensate for all the extra air coming in by enrichening the mixture, but cant, youve hit the limit, thats your rich mixture error
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Old 09-12-2019, 02:59 PM
Agcmrjazzy Agcmrjazzy is offline
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New boot will be in tomorrow and I will see if it fixes it.
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Old 09-18-2019, 01:29 PM
towertrash towertrash is offline
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I'd also check the DISA valve and all the vacuum lines in the CCV system too. Seafoam did wonders for me in all of the suggested comments
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  #10  
Old 09-18-2019, 03:14 PM
Agcmrjazzy Agcmrjazzy is offline
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Well I replaced the boot cleaned the icv and throttle body, and still the same. I have a intake cam sensor will be here tomorrow. I'm thinking the maf sensor is bad cause if I unplug it. It does idle somewhat better.
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Old 09-18-2019, 07:13 PM
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mattmar1 mattmar1 is offline
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have you tried clearing codes and seeing if anything changed after the boot replacement? can you read the MAF airflow at idle and post it in here?
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Old 09-18-2019, 07:18 PM
Agcmrjazzy Agcmrjazzy is offline
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the only thing I have to read my car is a Bluetooth adapter and torque app on my phone. yes I cleaned the maf and cleared codes still showing multiple misfires on all but number 2. this thing has me stumped badly
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  #13  
Old 09-19-2019, 05:57 PM
Agcmrjazzy Agcmrjazzy is offline
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This is after I reset the cel changed the intake cam sensor, new intake boot, cleaned icv and the dista I think that's what it is called. So what now
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  #14  
Old 09-19-2019, 06:02 PM
Agcmrjazzy Agcmrjazzy is offline
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And to that I drove the car once I put it in drive it seemed great, and drive great. So this is why I'm stumped only doing this at idle in park. Maybe the mass air sensor
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  #15  
Old 09-20-2019, 06:31 AM
jbarb jbarb is offline
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I would run a smoke test if you haven't done so already. While it could be other things, you'll want to rule out vacuum leaks before getting a bunch of parts (talking from experience...)
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