How do you adjust the mixture in a 1994 Honda civic ex? I know, I know, I need to get a Hanes manual already. My spark plugs are grey on the exposed parts, think Iâ€™m running lean. Is there a mixture screw I can turn or do I have to bring it in and have it tuned? It runs really rough in the low rpmâ€™s especially when it is cold. I installed a test pipe and a cat back, also a ram air intake. My car hasnâ€™t run the same since I tightened up my old leaky exhaust, but Iâ€™m not getting a check engine light like when my O2 sensor went out. Also, I canâ€™t feel my VTEC kick in any more. Can the solenoid get stuck open on the high rpm cam?