i had this problem 3 times! and every time this problem came along was when i used RESTORE engine additives. as soon as i added this product with new oil change and drive out , check engine light comes on and off , 1,2 time i didnt believe it , so i decided to change new oem vtec solenoide . and vtec .... damn i for got the name of that other piece! any ways both brand new oem acura dealer product. i did a oil change with fresh oil and after few month i decided i wanted to add RESTORE additives , to help with high mileage compression loss, and did a new oil change and added RESTORE, and took the car out for drive, and same problem came back!!! and noticed RESTORE additives will cause this problem as soon as u add them to our k20 engines, all that thick slime material which bonds to cylinder wall to restore compression , cause our vtec system to get clogged!