Hello! I’ve done some searching to find anyone with this particular symptom – and I didn’t turn up anything that was quite like this. In case it matters, my O2 sensor and Frequency Valve are not operational.

Symptoms:
• My car exhibits the pretty common idle hunt during warm-up. After a minute under load, or a few minutes of holding the throttle slightly open – the car will idle perfectly smoothly.
• Once idling nicely, if I turn on the Air Conditioning the RPMs are pulled down, and it oscillates just like when it is hunting during warm up.

I gather the first suspect should be vacuum leak – I plan on a smoke test (I am researching my options for performing this). A full vacuum line replacement is not too expensive. But I was wondering if the AC-related symptoms would lead someone to suspect a particular vacuum line segment / component.

I can’t find any guidance about how each the vacuum hose segment is replaced. Many are simple and obvious, and I assume the lines that connect directly to the thermotime switch will be a pain (requiring a trip into the VoD), but aside from those – are any vacuum lines particularly challenging? Should I be doing all: engine, and AC / brake related vacuum lines?