weird error code P1131 - unhelpful dealers please help!

[angelman]

Brief background here:2001 Pathfinder LE been working perfectly, always serviced at dealer, perfectly maintained. Engine starts knocking (we didnt realise that this was the sound we were hearing until later) for a few months.One day dumps oil and starts blowing white smoke. Engine is hosed, one cylinder is completely destroyed and melted. Engine gets rebuilt.Various issues with computer calibrating to new engine. O2 sensors get replaced twice. All is going well and then engine light comes on again. Then the computer dies. A new computer is installed. All is wellNow all seems fine again except engine starts knocking again. Check engine light is off.After a month or so of driving check enging light comes on again.Now this mysterious error code is reported P1131. The mechanic has checked the swirl control valve and the vaccuum line to it (since this code indicates a problem there in other nissan cars) and there was absolutely nothing he could find wrong with it anywhere. So now we are at a dead end again. We have already invested several thousand dollars in this car rather than buy a new one since the rest of it is in perfect condition.Dealer is generally useless ripoff but our mechanic can do no more. He reckons the new computer needs a firmware update but dealership wont do this without doing their diagnostics (for $110). We have already checked just about everything on the car, everything is working fine. Everything has been checked for vaccuum leaks, oil leaks etc. etc.The fuel economy has been poor while the engine has been knocking so there obviously is a problem. Some sensor is not right or the computer is compensating for a problem either real or imaginary.Any ideas on this puzzler?

[fueler]

p1131 - per nissan - "Swirl Control Solenoid Valve" thats a different valve from the swirl control valve. There's a swirl control valve, and then there's a swirl control SOLENOID valve. You or your mechanic needs to check/replace the swirl control SOLENOID valve.

[fueler]

also - your 1 cylinder knocking problems could very well have been due to a bad coil. Just a guess.