162,000 miles and counting here. 2003 EX, been driving off road for over a year now with it. It needs a new tie rod assembly pretty soon I reckon. Struts next. It's VERY wet here in this tropics and I've had a few electrical issues, but I'm loving the car overall. Solved intermittent VTEC issues by using a heavier weight oil and putting seafoam in the oil to increase pressure. It's been running great! Will possibly clean out the top of the engine block and check the timing in the future. Whatever it takes to give it love and keep it running <3
Hammerheart: Thanks for your input here. My '03 EX has had a P2646 and went into limp mode twice intermittently, but both times it went away by itself and has been gone for ~ 2 1/2 months now! I haven't changed anything! Go figure!
One question: Did you add the Seafoam to increase the oil pressure; or did you add it for it's ability to break down and dissolve any particulates that may end up in the screens?
I just added 5 ounces (as directed on the can) of Seafoam to my oil yesterday, and we'll see what happens. The oil currently has ~ 4500 miles on it and still looks to be rather clean. The oil I'm using is Valvoline Synthetic Blend 5W20, with a quart of the thin Rislone oil additive. I've been using Rislone since the '70's in my cars with good results. Rislone too, with it's increased detergents, is good for breaking down deposits inside the engine. But I doubt that it would have any effect on the oil pressure.
I'm guessing it went intermittent because the screens may be partially clogged. But, ????????????????????????
So my plan is to wait another 500 miles or so to see what the Seafoam does, when I go to change the oil I'll also remove the VTEC solenoid to see what's going on with it's screen and electrical connections, stick with the 5W20 Valvoline, skip the Rislone, and go with a Wix oil filter instead of the cheap Fram I had before. I can only hope that fixes it!
One thing for sure: That P2646 code can sure give us a lot of grief! There seems to be any numbers of issues that set it off! And the opinions on how to solve it here seem to run the gamut as well! Some say never use anything other than 5W20, versus like your suggestion to try 10W30. Some say never use any oil additives, versus your suggestion with the Seafoam.
There are two things most everyone here does agree on though: stay away from cheap oil filters, and only replace the VTEC solenoid with a genuine Honda part.
Please let me know, Thanks! : - )