90 sc won't idle when cold

I went out to start my car the other day and it started up easy but after running for a minute the engine rpms dropped to 500 and almost died and then went up to 1000 and dropped back down I kept doing this until it warmed up I couldn't find vacuum leak it blowing a code but haven't gotten the chance to snag an obd1 scanner .

Check for vacuum leaks... I had the same problem and had to re-do all my IC tubes with copper gaskets.

I did I couldn't find my car had a code 31 which is evp/pee volts lower than min. No idea what that means

31 O,C,R EGR Valve Position (EVP) sensor out of range (low)

See if an auto or tire store nearby will test eec codes for free.

Full code list, SC specific, here: http://www.njtacc.com/tech/eec_codes.html

Unfortuneatly no garages around here have obd 1 ford testers lol