Re: 86 535i (E28) Running Rough

[alex.fadeev@xxxxxxxxxxx]

Terry Peterson <tpeterson99@domain.elided> wrote:
> I have an '86 535i that started running rough after the
> battery was disconnected and then reconnected again.
> This has happened to me twice in the past 2 months.
>
> The first time I removed the battery to try it in a friends
> E28 that had a dead battery.
> After I put it back in my car, It ran very roughly when I
> started it and I had to keep my foot on the gas to keep it
> running.  After a few minutes of this it smoothed out and
> ran fine.
>
> Last week I disconnected the battery so I could remove the
> instrument cluster to replace the service indicator batteries.

Terry,
You did not need to unplug the battery for that.

> When I reconnected the battery and started the car it ran
> very rough and I had to keep my foot on the gas to keep it
> running.  It runs rough at idle and at higher rpms and it
> still runs bad after it warms up.
>
> I checked for vacuum leaks, I checked all of the electrical
> grounding and I checked the idle control valve and found no
> problems.  Does anyone have an idea what this could be?

What you experience is normal.
When you unplug the battery your DME looses all of its adoptive settings
and need to re-adopt to your car.
There are a few separate maps in the DME for idling, driving with partial
throttle, with AC on, WOT. Probably many more. It will need to re-adopt all
of those maps.
This process takes anywhere from 30 seconds on newer cars to 10-30 minutes
on older ones.

Give it time and the smooth idle should return. If it doesn't, then you've
got real issues.

alex f

------------------------------