I just replaced the thermostat housing and water pipe on my 07 R56 S.

To get plenty of room I removed/moved the following:

1. Disconnected battery ground
2. Removed CAI inlet
3. Removed airbox and turbo inlet system
4. Disconnected typical connectors to free up the wiring harness (as seen in multiple instructional videos)
5. Disconnected, what I assumed to be the ECU connectors (box to the left of the fuse box) to make the area more accessible
6. Removed intake manifold to get better visual/physical access to the water pipe

From this point I replaced the thermostat and water pipe and re-assembled.

Once put back together, loaded with proper coolant, and appropriately bled I started the engine. The engine fired right up but the idle surged RPM slightly for about 30 seconds...revving slightly up, then down, etc. after which time the idle became rough. Applying throttle evened it out, but as soon as the engine returned to idle it got rough again.

My code reader pulled P0300, P0301, P0302, P0303, and P0304...misfires.

What I've checked so far:

1. Verified all electrical connections (that I recall and that were obvious)
2. Pulled the camshaft sensor, inspected and clean for good measure
3. Pulled a couple plugs and verified that they were in good shape

I hoping that the members here can provide some guidance on what I should check next.

Thanks in advance.

 

the revving up and down is a sign of vacuum leak. check the lines SPECIALLY the ones under the intake manifold. Also, make sure the plug that sits on the ECU bracket is also connected.

 

Interesting that you mention a vacuum leak. After posting last night I discovered a crack in the brittle vent hose running from the crankcase to the intake manifold. I put an order in for a new one this morning, should have it in a day or so.

The other items you mention are all firmly connected.

Thanks for the reply.

 

Yeah that's usually the case with these hoses. The cold side intake pipe to the turbo also cracks amd causes unmetered air fault.

Sometimes I feel like relocating that vacuum canister and valve to be better accessed.

 

Just a quick follow-up on this thread... Replacing the cracked crankcase ventilation hose fixed the issue.