M52 misfire after first minute of driving

[MrT8064]

I've finally got my M52 up and running. For the first minute or so, the engine pulled incredibly smoothly and there was plenty of power.

After this, it felt like there was a judder, or misfire meaning acceleration became that of my old M42!

I've driven it several times since, and it always seems to run well ”“ when cold ”“ for the first 30 seconds to a minute, then start misfiring/juddering.

Any pointers would be a huge help!

[Brianmoooore]

To fit the M52 into an E30 you should have disconnected the wiring to the section of the coolant temp. sensor that worked the temp. gauge in the engine's original home, and connected it to an E30 'brown' temp. sensor.
Are you sure you haven't disconnected the section of the sensor that controls the ECU by mistake?

[MrT8064]

I bought the engine with the brown temp sensor already installed. And I think I plugged them both in right. From memory it's the single pin one. Does this look right to you?




Any other ideas? Cheers

[Supafly]

If the car was outside while you were working on it then check the spark plug wells aren't full of water. Also worth checking the plugs as on my m20 I replaced everything only to find that it was the one month old ngk plugs that were failing when warm (60 seconds after startup).

[MrT8064]

I actually checked the spark plug wells yesterday - and found water in two of them! I've ordered a new set and will hope they fix the problem