Tech gurus, help requested - 2003 360 F1 CEL flashing, mis-fire codes

F-chat Tech Gurus, need your help! Any thoughts, suggestions and problem solving ideas appreciated! See below:

1. Initially, the CEL on my 2003 360 F1 was triggered and the OBD2 scanner showed a P0300 (random misfire) code; I cleared the code and set my scanner in data log mode to see if I can replicate the problem (to isolate whether it is a one time or systemic fault);

2. After clearning the initial code - I went for a 2 hour drive and observed the CEL flashing intermittantly under light throttle load on the highway (usually at approximately 3500-4500 RPM);

3. When the CEL starts to flash, it will stop when I increase the throttle load (e.g., by flooring it or going 3/4 throttle) but reappear again once under light throttle conditions; this occurs both when the car is cold and when up at normal operating temperature;

4. Readout from the scanner (it was logging in real-time mode) shows "PENDING" codes for P0300 [random misfire], P0306, P0307, P0303 and P0302 [cylinder misfires for 6, 7, 3 and 2] in that order resident in the ECU, but CEL is currently not illuminated....just flashing iunder light acceleration/disappearing as described above;

5. During the drive (and once a flashing CEL incident occured), I pulled over and took some measurements of the engine manifold temperatures using my IR temperature probe - each cylinder was running within +/- 20 degrees Fareinheit (i.e., doesn't appear to be any particular cylinder running hotter/colder than the other). Cat temperatures were both around 400F (were +/-20 degrees of each other);

6. Spark plugs (NGKs) are about 5 months old and have about 7k miles on them - they have been removed and examined with no real obvious/unusual wetness, white marks, carbon deposits, etc.

7. No real obvious/unusual mechanical noises emanating from the engine compartment. Given it seems to be sporadic CEL flashing, leaning towards ruling out a mechanical failure of some kind (e.g., valve spring broken, etc.) but that's early thinking;

8. Other notes - car has 17k miles, annual service (fluids, plugs, filters) this past 12/2012 and recent clutch change

Any thoughts/ideas on what might be triggering this and what to check for?

Many thanks in advance for your help and comments!

 

Thank you!! So far, Tony @ TandR identified a leaky intake gasket around cylinders 6 and 7...and is working to swap them out now and - fingers crossed this is it, will post final developments.

 

Quick update: intake gaskets were confirmed to be leaky (via smoke and propane test) and new ones installed today, but problem still persists...stay tuned for more developments

 

Just wanted to close to loop on this thread - thanks to everyone for their help! So, in the end, it was the intake gaskets on the drivers side (LHD) that went bad and were leaky coupled with a stubborn ECU that wouldn't clear the codes even after the fault was cured. The last bit required a reset/reflash that finally cleared the codes from memory. Car now drives like a champ!