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Agcmrjazzy 09-11-2019 01:52 PM

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.

Chedley 09-11-2019 03:38 PM

Yes, clean up the throttle body with carb cleaner, replace that broken hose, reset the adaptations.
Then test drive.

Agcmrjazzy 09-11-2019 04:15 PM

Reset adaptations meaning what? And the intake is clean. From what I have seen it's the hose going to the idle control valve.

mattmar1 09-11-2019 05:31 PM

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.

Agcmrjazzy 09-11-2019 06:40 PM

1 Attachment(s)
This is the intake boot that goes on the throttle body. The small hose is the one that broke off

jbarb 09-12-2019 06:07 AM


Originally Posted by mattmar1 (Post 13103763)
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.

mattmar1 09-12-2019 01:43 PM

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

Agcmrjazzy 09-12-2019 02:59 PM

New boot will be in tomorrow and I will see if it fixes it.

towertrash 09-18-2019 01:29 PM

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

Agcmrjazzy 09-18-2019 03:14 PM

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.

mattmar1 09-18-2019 07:13 PM

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?

Agcmrjazzy 09-18-2019 07:18 PM

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

Agcmrjazzy 09-19-2019 05:57 PM

1 Attachment(s)
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

Agcmrjazzy 09-19-2019 06:02 PM

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

jbarb 09-20-2019 06:31 AM

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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