I just got through my first afternoon working on an '89 sedan that I just bought with some insurance settlement money. Since this car was apparently extremely well cared for (2 POs, who both serviced it regularly at the dealer, the first owner had an oil pressure gauge installed so that bodes well for his consciousness about maintenance), and the 60K maintenance was recently done with timing belt & tensioner, I decided just to clean the throttle body, idle air valve, and flame trap. The old flame trap had been removed, and the little plastic case was pretty dirty inside, especially with the small little vacuum tube that comes off the side. That was completely plugged up, so I cleaned it all really well and put a new flame trap in for good measure. The throttle body was really dirty, probably never cleaned, so I cleaned it up really well, and I even took out the throttle plate and beveled the leading edge of it. The idle air valve didn't look too bad, but I cleaned it up. I also noticed a few vacuum lines getting cracked at the end, so I trimmed them up so there wouldn't be any problems.

So when I get this all back together, it runs better but the idle is way high, probably over 1K. Being an LH 2.4 setup, there is no base idle adjustment. Since this car is automatic it makes it pretty aggressive when you take your foot off of the brake. I'm just wondering what I could have done to cause the high idle. I doubt highly that the throttle plate was reinstalled improperly, and I don't think I could have damaged the idle air valve. A vacuum leak seems like a possibility, but I really think if anything I improved the vacuum situation. Any ideas?