tayto

I have cleaned the throttle body and iac. All vacuum hoses have been replaced. Pcv has been replaced along with all the hoses cleaned out, they were pretty crusty. I reused the iac and throttle body gaskets, they were not ripped and the thing runs to good at idle to have a vacuum leak IMO. I was also thinking about running some cleaner through the iac while running as described in the shop manual. I do all city miles and drive about 20 minutes one way, I'm getting 18 mpg which I'm not happy about.

Like most factory tachs mine reads incorrectly. This is why I checked it with my timing light which displays engine rpm. It was ~700 rpm when fully warmed up and in gear, right within factory spec.

CTS has been replaced with a OEM replacement. Idle rpm on the dash shows 500 when in gear. I hooked up my timing light and it showed closer to 700. I trust the timing light vs the gauge in the dash. Sometimes idle increases when shifting to neutral or park, sometimes it stays the same.

Have only had this happen a few times on my '97 Legacy 2.2L with 200,000 Km on it. It has only happened after the car has sat for 30-45 minutes after running and up to temperature. It has only happened a handful of times and does not do it everything. The idle will fluctuate from 700 to 1200 rpm. A quick flick of the throttle or putting the car into gear will bring idle to normal. Besides that the car runs great aside from "AWD" fuel economy. Recent work done in the past 4 months: timing belt, oem spark plug & wires, oem CTS, oem front o2, air filter, fuel filter, cleaned maf throttle body egr and iac. All work done by me. Only thing I have not checked or adjusted is the tps.