Hi, I've gained so much information from this thread. I just wanted to add my experience with this problem in case it helps anyone. Sorry, it's a long one!
I have a 2008 EX AWD Automatic Transmission with about 145k, 80% oil life since last changing. Returning home from Flagstaff to Phoenix AZ last week, just after filling up the gas tank, I got the Check Engine Light (CEL). I pulled over, checked the manual and decided to check the gas cap. Wasn't loose. The light stayed on but I decided to continue on since the car was driving ok, and the manual suggested that it might be an emissions problem that I did not necessarily need to immediately deal with. But when I got back on the road and accelerated, the car VSA light and the exclamation point triangle came on accompanied with the shuddering and 3000 rpm limiting experience described by many others in this thread. I pulled over, shut off the car and took a look around the car to see if there was anything obviously wrong. FYI, I had just replaced the radiator with a new OEM one and when I did that, I also drained and refilled the transmission fluid. That was just prior to this trip so I assumed it had something to do with that. But the temp gauge was always below halfway and there were no leaks anywhere. Plus it made the 150 mile drive up to Flagstaff two days earlier, no problem. After looking around and not seeing anything obviously wrong, I started the car back up. Only the CEL light was still on and the car drove fine though all the gears. So I decided to risk the 2.5 hour drive to Phoenix. About 20 minutes in, the other two lights came back on, and the car shuddered, etc. Luckily, I had a friend who lives near that exit, so I took the car there and hitched a ride home with the in laws. Over the last week while the car sat at my friend's house, I researched the issue by reading every page of this thread and watching several videos on this Honda VTEC issue, some linked in this thread, some not. I ultimately decided the best thing to do was to replace the entire spool valve assembly with the Honda OEM 15810-RAA-A03 plus a few other things. The genuine Honda spool valve assembly cost me about $180 from my local dealer. I also decided to change my oil with Honda 5W-20 and Genuine Honda oil filter. Here's what I did:
With the front of the car on jackstands about one foot up, I removed the negative battery terminal. Then I loosened the 10mm bolt that holds the power steering hose bracket in place and used a bungee chord to hold it out of the way. I then removed the spool valve by first unclipping the plugs and used needle nose pliers and a flat screwdriver the remove the wires that are attached to the unit. Then I removed the three equal length 10 mm bolts with a socket and short extension. The screen on the spool valve looked pretty clean, no chunky debris like some others had. One of the videos I watched suggested to crank the engine over for a couple of seconds with the spool valve removed to purge any oil that was in the small tube leading to the screen in case there was debris there. This might have helped, but if you do this, be prepared for an oily mess. Even though I was holding a rag there, I spend hours with rags and simple green cleaning up the oil that surged past the rag all over the engine compartment and ground. Some oil got on the plugs for the spool valve assembly too, which I had to clean. I'm not sure I suggest doing that part, but like I said, it might have helped. After the mess was clean (and the engine compartment cleaner that it was before), I installed the new spool assembly. Then I drained the engine oil and removed the old oil filter. Then I filled it with about 4.5 qts of oil and put on the new oil filter. The engine started up, no lights came on, and after a few cautious miles driving around the area, I drove it back to Phoenix with no issues. I'll be sure to follow up if this fix doesn't hold up but, it's gone about 200 miles so far, finger crossed it goes another 140k miles like this!
