E30 Zone

Hi guys, my 1991 316i has an intermittent misfire, mainly when cold. It bogs down when first started (maybe a separate issue) and then badly misfires when idling and accelerating. Intermittently it clears and all is fine, then it might come back again.

It's been gradually getting worse recently, so I removed and cleaned the throttle body, intake pipes, IVC at the weekend (no change) and then fitted a new coil pack a few days ago. This seemed to clear the bogging at startup and misfire when cold completely.

24hrs later (this morning) all the issues are back again! Any thoughts what to check next?

Have you checked the Blue sensor seeing as it has a problem mainly when cold?
Likewise check the TPS is working properly.....check these items at the ECU connector.

Also could be a bad CPS.

Check for air leaks all around the intake area and I would suggest that copper NGK plugs are used and OEM plug leads.....distributor cap and rotor OK?

You may need to check the timing belt is tensioned properly and that the timing is correct.

Could be a bad AFM also.

You mention it 'bogs down' in your OP. Your interpretation of the meaning of "bogging down" may be different from mine, but using my version, "bogging down" under acceleration on an M40 engine is often a symptom of a faulty distributor cap and/or rotor arm.

Cheers guys, I'm doing a cambelt and waterpump change this weekend so will eliminate this. At the same time I will check the cap and rotor. I've yet to check the blue sensor but looks as though I should. My issue is spending too much money on the car. I've already spent more than I paid for it by giving it a major service, new coil, cambelt, waterpump and PAS pump.

When I say it bogs down, I mean the revs dip very low when I first touch the throttle after start-up. Once I'm moving it doesn't bog down. That's when the misfire starts...