ECU gets Hot

[Sjoerd320i]

Well, just like the title says actualy...

A few weeks ago I had the first test drive with my car and all went great until after about 30 mins it started running on 5 cilinders.
Changed the coil, plug, injector and tested if the injector gets power. Everything was ok but still running op 5 legs.

I then changed the ecu with a mates 525, started the car and nothing wrong, running perfectly on 6 cilinders.

When I pulled my old ecu out I noticed it was VERY hot! and the one I pulled out my mates car wasn't.

I bought a "new" ecu from a lad in Belgium and fitted it the other day and the car ran fine again.
When I felt the ecu again after a 10 min drive it was already starting to get warm again so I stopped the car.

So the question is, what could possibly be the reason it's getting so hot.
Could it be a bad coil?

Edit: couls it also be that the ecu needs to be grounded? As its now just lying in my glovebox.

[craigieeb]

The ecu normally gets "warm" but not hot, (how hot are we talking here)

and im not 100% sure but I think it should be earthed, not for any internal connections, but just for safety ....?

mebbies have a look at your wiring again, just incase there is something dodgy lurking about

[DanThe]

Check your earths for a start, case doesnt need to be earthed but its best to have it mounted on a bit of a heat sink

[Sjoerd320i]

It gets to hot to hold so I dont think that will be solved by a heat sink but I will get one and stick it on as I can't harm.

Witch earth connections should I check, as far as I know everyting is connected properly.

[DanThe]

The engine loom earths