Could be a lot of things...

You need to have proper voltage - weak battery or could voltage regulator. Fuel wise, I'd guess it has an intake leak with the cold start valve (there is rubber part). At that age- I'd be replacing the injector seats too.
Measure the resistance of the temp sensor (need to know the temp) and compare to factory spec.

All very easy.. just take your time. Yep you can clean the Aux airvalve whlle you have it apart. Symptom would suggest a small split in the coldstart hose- or possibly another vacuum elbow etc.. those plastic lines crack with age too.

Michael