Just gussing here, I'm totally unfamiliar with your car or engine:
- A ground issue affecting one bank only?
- Some other electrical component that is "one per bank" (my older volvo has two ignition amps, one for 1-3, one for 4-6).
If you're not sure your fan is running it might be good to make a manual check.
The 320 has a coil pack per cylinder and 2 spark plugs per cylinder. not sure that there is only one earth per bank but I'll go have a dig around.
The temperature seems to be standard so it's appears to be just once that heat soaks through to all the components ...... kind of points to the Ecu again.
Ran the car up to 'failure mode' yesterday, got cylinder 1 misfiring. Disconnected the coil from the harness by unclipping the connector, misfire did not change in the least so it looks like that signal was not getting to the coil! Plugging it back on did not clear the misfire.
turn off, turn on and it's gone. but came back shortly.
Disconnect again ( engine off ) connect to spare coil pack with leads and plug attached, start engine, plugs firing cleanly???? One would think a duff coil pack but the one on the engine is the new one!
I am pretty convinced that the ECU coil drivers are on the way out
Anyone know what the actual repair is to the output drivers? Replacing mosfets or something?
Just found this .......
SLK (from 1999) C class (from 2002) suffer from 'check engine' light illuminating with PO30/32 codes (misfire). This is caused by defective soldered spur connection in wiring harness (+12V feed to coils). Resolder to rectify.
Anyone know anything about this fix?