m52b28 misfire :(

[Supafly]

I've just completed swapping an m52 (out of a running e30) into my e30 and it has a misfire from idle and as you rev, bad enough to make the car shake on idle.

It didn't have the problem in the donor car, and everything has stayed the same. Inlet hasn't been off either.

So far I've cleaned the maf with electrical contact cleaner as it has a cone filter, checked for air leaks with carb cleaner around the inlet pipes, t/b, inlet manifold. Checked wiring connectors by injectors(lambda), exhaust manifold(twist connector for coils?), afm, t/b, fuel evap valve.

I've just ordered a set of plugs and I've been sent out four! this was after confirming that it is a six cylinder. I was planning on giving up for the day... but I just can't. Sent a mate out to get me another two plugs and planning on changing them to see if it makes a difference, although as nothing has changed I can't see why there should be a problem but for the sake of a set of plugs I thought why not.

If anyone has any ideas on what else to check or if there are any common causes I would really appreciate any pointers

[Supafly]

Not sure if it's relevant but the oil level light on the check panel used to illuminate on the donor e30 but doesn't on mine. There is no oil level sensor fitted to the sump.

[Supafly]

Just in case anyone searches for a similar problem...

Somehow water has got into the last three spark plug tubes closest to the bulkhead and sat there waiting to mess with the spark. Dried out, new plugs and now all good.

Not sure where this could have come from as the engine has been under bonnets at all times. I still have my elephant trunk drain in place, and I think the donor car had it fitted also, but can't be certain as it's in bits now. My car was parked with the nose in the air, as I put the engine in from underneath, other than that I can't think of how the water got there.