Runs shite from cold & flashing lights

[oomz1975]

Couple of issues that are annoying & need attention...

Firstly on occasions, start up from cold, the cars runs like dogsh*t for around 5/10 mins or until warmed up.
It stutters, coughs, farts, revs slowly & generally feels like its mis-firing.
Once warmed up, it runs as sweet as a nut, no problems at all.

Secondly, I have noticed the dash lights & switches are flickering constantly. Is this a symptom of weak battery or dodgy alternator?

Cheers

[pianist]

If it stutters to low revs the alternator wont be able to produce sufficient power and charge light plus all other lights on dash will light up, therefore if engine is jumping up and down from hi to low revs the lights might be flickering.

First of all it would help if you tell us what car and engine it is, but i would start by looking at ICV (Idle Control Valve)

[oomz1975]

Just remembered...

1990 325i m20

Already checked the usual plugs, leads, battery cables etc.
Also cleaned the throttle body & ICV, checked the tps.

It idles fine, just runs rough when pressing the throttle pedal.

[Speedtouch]

Check the notorious blue temperature sensor as a first port of call.

http://www.e30zone.net/e30zonewiki/inde ... emp_Sensor

[oomz1975]

Check the notorious blue temperature sensor as a first port of call.

http://www.e30zone.net/e30zonewiki/inde ... emp_Sensor

Good shout, will check it & report back.

[Grrrmachine]

Actually, I would expect one thing to be causing both issues, and that would be a failing diode pack in the alternator.

[oomz1975]

Actually, I would expect one thing to be causing both issues, and that would be a failing diode pack in the alternator.

I will run a test on the alternator too, thanks.

[Brianmoooore]

I will run a test on the alternator too, thanks.

Not easy to test without an oscilloscope. A failed diode puts a large AC component into the alternators DC output, which confuses the average test meter.

[steve_k]

I could be wrong but wouldn't it be easier to replace the alternator with a new one & see if the symptoms continue??

[Grrrmachine]

No, because swapping parts over can introduce new problems, and is also the most expensive way of trying to fix the issue.

A failing alternator will usually show up as a pulsing of the headlights at idle, although as Brian says a proper diagnosis needs serious tools. If the charging system is good, Speedtouch is on the money with a duff temp sensor.

[Fred555]

Just set digital multi meter to AC Volts and see if it picks up a reading.

[oomz1975]

Replacing the blue temp sensor with a new one has sorted the rough running issue.
Got a new voltage regulator to sort the flickering light problem.
Happy days

[Speedtouch]

Good to hear that, fella.