I have an 1988 accord LXI. Over the weekend I changed the oil and air filter. Now the idle will race up to 2000rpm's then drop down to normal 800 or so and then race up to 2000 again. This just keeps repeating. When it gets to 2000 it drops right down and then goes right back up. Does not remain steady for more than a second at each end. Any suggestions? I looked for a loose vacuum hose already.