Temporary rough idle

Smartbear · Post by **Smartbear** » Wed May 18, 2022 9:33 pm

flybobbie wrote: ↑Wed May 18, 2022 9:02 pm That is what i am thinking.
Looks like a a smoke machine or cigar testing job.

If you’ve got the right diagnostic kit you could check the fuel trims to see if the car’s been adding extra fuel to compensate for an air leak.
Rob

flybobbie · Post by **flybobbie** » Wed May 18, 2022 9:36 pm

Will look at that.

flybobbie · Post by **flybobbie** » Wed May 18, 2022 10:38 pm

Looks like it is fitted with a vacuum pump.
https://www.realoem.com/bmw/enUS/showpa ... Id=11_3758

javis20 · Post by **javis20** » Mon May 23, 2022 1:36 am

Again, have you checked the plug to the eccentric sensor? Is it leaking?

flybobbie · Post by **flybobbie** » Mon May 23, 2022 6:44 am

I will check that today.

flybobbie · Post by **flybobbie** » Mon May 23, 2022 10:40 am

I remember now i checked it when i replaced the servtronic seal. It was dry.

I will try disconnecting air flow sensor, let it run in default, see what happens.

flybobbie · Post by **flybobbie** » Mon May 23, 2022 1:23 pm

Well disconnected mass air flow connector, from cold, engine started normal, straight to fast idle and slowly dropped to 600.
No hesitation or wobbly rpm, even engine was smooth.

Have tried cleaning in the past, looks like just buy another.

Well ordered a VDO Continental.
See if that cures the problem.

flybobbie · Post by **flybobbie** » Fri Jun 03, 2022 10:46 pm

Fitted new sensor.
Has made a difference, just watched some videos i made. Not jumpy, but just doesn't seem to do what it has done in the past.
Normally goes to 1200 smoothly then slowly falls back over about a minute as it warms up, to be stable at 600.
Runs slightly better through all other rev. range.
Did notice when alternator kicked in it shot to over 15 volts for 3-4 seconds before settling at 14.7, at which point idle stabilises.
All a bit odd.

I think i need to check battery volts before the next start.

Smartbear · Post by **Smartbear** » Fri Jun 03, 2022 11:32 pm

flybobbie wrote: ↑Fri Jun 03, 2022 10:46 pm Fitted new sensor.
Has made a difference, just watched some videos i made. Not jumpy, but just doesn't seem to do what it has done in the past.
Normally goes to 1200 smoothly then slowly falls back over about a minute as it warms up, to be stable at 600.
Runs slightly better through all other rev. range.
Did notice when alternator kicked in it shot to over 15 volts for 3-4 seconds before settling at 14.7, at which point idle stabilises.
All a bit odd.

I think i need to check battery volts before the next start.

The ibs system varies the alternator output according to the state of battery charge, it also lessens it under acceleration & increases it on the overrun

Rob

flybobbie · Post by **flybobbie** » Sat Jun 04, 2022 7:39 am

I have watched the volt meter whilst driving and it never varies from 14.5-14.7 volts..
Perhaps it varies the current.
But if the battery is ageing, and BMW docs suggest at 5 years an agm battery is only 80% new capacity, the system might just be charging all the time.

I'm going to try and clean the vanos filters later.

Interesting i have a small motorcycle battery that needed charging. I tried a 0.6 amp trickle charger and it wouldn't charge.
Tried a 4 amp car charger and it charged up.
Shows that batteries need some amps to get charging if low.

I wondered what would happen if i re-register the old battery, whether the system would charge it at a higher rate.
The battery might be more robust to charge than BMW give it credit.

Smartbear · Post by **Smartbear** » Sat Jun 04, 2022 2:52 pm

flybobbie wrote: ↑Sat Jun 04, 2022 7:39 am I have watched the volt meter whilst driving and it never varies from 14.5-14.7 volts..
Perhaps it varies the current.
But if the battery is ageing, and BMW docs suggest at 5 years an agm battery is only 80% new capacity, the system might just be charging all the time.

I'm going to try and clean the vanos filters later.

Interesting i have a small motorcycle battery that needed charging. I tried a 0.6 amp trickle charger and it wouldn't charge.
Tried a 4 amp car charger and it charged up.
Shows that batteries need some amps to get charging if low.

I wondered what would happen if i re-register the old battery, whether the system would charge it at a higher rate.
The battery might be more robust to charge than BMW give it credit.

My battery is only a year or so old, i watch the voltage via an in car display & it varies from 12.7 to 14.7 depending on driving conditions/charge in the battery

Rob

flybobbie · Post by **flybobbie** » Sat Jun 04, 2022 5:52 pm

Mine never changes.
Just done another learn reset, seems a lot better will leave it at that.

flybobbie · Post by **flybobbie** » Mon Jun 06, 2022 9:29 pm

Well perfect now, idles normal.
Did another adaption reset.
Drive down local B roads to friends at 50mph got 50.1mpg, never seen that no matter how carefully driven.

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