low voltage causing 1271 error code???

[colin86325]

My 1991 318iS has increasingly been flashing the Check Engine light when I come to a stop sign. A stomp test reveals only 1271--ignition coil #1.

When the Check Engine light flashes, the other lights on the SIL board (Oil Service, Inspection) flicker brighter and the idle falters slightly. The Check Engine light comes on only when the car is stopped, or during coast-down around 2000 rpms. If I keep the rpms up at a stoplight I can get the Check Engine light to go away.

When the headlights are on, there is no Check Engine light whatsoever. The car idles better as well. I'm wondering whether the additional electrical load is somehow causing a marginal alternator to operate correctly?

I'm kind of confused whether this is a ground or an alternator issue, so any clues would be great. I'm thinking that when the voltage dips that the #1 ignition coil starts acting up as well, which results in code 1271.

[colin86325]

Well I measured the voltage at the alternator and it was all over the damn place. It spiked up to 15.8 and went down to 13.2 within a second's time. I barely could read the numbers as they were displayed.

I ordered a new voltage regulator and will update the thread.

It seems that the load from the headlights had a stabilizing effect, but other things like all the lights in the dash would flicker brighter and then go back to normal.

[colin86325]

Ended up replacing the alternator and now no more check engine light.  Everything is back to normal.

[Kellu]

The e36 318is I'm buying tomorrow does pretty much the same thing. I started it and put it in reverse and it started almost dying and when i pushed in the clutch and revved it up above 2000rpm is idled normal again. I'm thinking the alternator is my problem as well. Hoping that when I replace it the check engine light will go away.

[colin86325]

Sounds like that's the problem.  I'd measure the voltage at the alternator first though.

[Kellu]

Sounds like that's the problem.  I'd measure the voltage at the alternator first though.

Replaced the alternator and still dying out. Think it's the battery?

[colin86325]

Most auto places can test your battery for free.
There's also a ground cable from the alternator that can corrode internally but still look ok externally.  I had this problem on 2 M42 cars.

[Kellu]

There was only two cables to my alternator...

[Kellu]

I also checked the terminals and there was very little water. As far as that ground cable goes he had some 12g speaker wire acting as a ground.

[colin86325]

Haha, well i suppose speaker cable is better than nothing.  Barely! 

It sounds like your battery was marginal as well.  Give us an update once you get everything squared away.