M20b20 slight misfire and hunting idle

[Onure30]

Ive been trying to sort out my e30 for the last few months and what ever ive done hasn't made the slightest of improvements .

Its runs and idles but when i rev it itll misfire slightly and also it runs rich.

Ive changed
Spark plugs
Afm x3
Coolant sensor
Rebuilt throttle body
Intake boot
New icv

Still doing the same thing, it also hunts idle ever so slightly.

My last resort is ecu which im suspecting,
Upton removal and inspection i found some water damage on the ecu board, can this be the cause of all my problems?

Looks to me like there is two missing capacitors on c805?

[Speedtouch]

Yes, any water ingress into an ECU won't do it any favours! You could try carefully brushing away the corrosion with a nylon brush and use electrical contact cleaner simultaneously, which may cure or highlight any problem, such as dry solder joints. etc.

Which ECU do you have, e.g. 0 261 200 172 ?

[Andyboy]

A used 320i ECU will be cheap enough so I'd just replace it.

Also, only use Bosch coolant temp sensors as even the 'known good brand' aftermarket stuff can be absolute crap. I fitted one from febi and it failed in a few days.

Ditto aftermarket idle control valves. The Chinese ones are absolute shit and the 'made in Germany' LOWE Automobil ones aren't very good. Bosch no longer make them and BMW seem to have them all - a mere £422, thanks. You're better off with a used Bosch one although with some extra plumbing, an M50/62/54 one does the job.

[Onure30]

Ive had a more thorough look today and its seems to be surging and misfiring while reving between 2-3k. And once warmed up it seems to stop surging but misfire is still present.

[Speedtouch]

Most likely a problem with the ECU, but also check the cambelt timing is correct.

[Onure30]

Received the new ecu (172) yesterday and fitted but its still same.
Its like the engine struggling to idle. Surging badly but then when it warms up its not that bad

[Speedtouch]

Perhaps try cleaning and refitting the original ICV if you still have it...

[Tzantushka]

Frustrating as you’ve thrown a few parts to get to the bottom of this.

I would check ignition, air and fuel systems end to end first before more parts. If the timing belt is sound, start with ignition, as that is a likely culprit from your description. Check the cap and rotor first for wear, looseness or arcing. Then the measure the coil and plug leads if they are in spec.

Then I would look at the intake for leaks as the surging may be a separate issue. Rent a smoke tester or look up DIY video. That will rule out intake leaks

[Tzantushka]

Aargh. Duplicate post from the phone…

[Speedtouch]

Indeed. You could even try running the engine in the dark, to see if there's any ignition stray arcing going on...

[Onure30]

Update.

I thought i found the problem which was the two injectors, the pintle caps had come of and was resting in the injector seats on the intake, i had to remove the intake and upto removal i found the vent tube o ring damaged.

I replaced all and sorted the injector but unfortunately its still the same!

Im thinking to compression test it as you ve given everything to it and its still the same. Hunting on idle and running really rich.

[Tzantushka]

Is it still misfiring?
And have you worked through checking all the ignition components?

e.g coil in the Wiki article?
https://www.e30zone.net/e30wiki/index.php/Ignition