Q: Check engine light on 1990 Ford Mustang GT

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when on the interstate my check engine light comes on and goes off every once in a while. I just had motor rebuilt new tranny new clutch new O2 sensors I am lost. The only thing I haven't replaced is the fuel pump and fuel filter.
(1) Answer
(2) Comments
if you are changing altitude , the o2 sensors could be reacting to thinner air. it was not uncommon for obd 1 systems to re act like this.
have it double checked at a shop to confirm.

The altitude isn't changing. It started after heavy rain but on the coast here there is no change in altitude
ok, then you need a shop to pull the code with an obd 1 tester to get the code and diag it to determine the issue. if you give me the code, i can guide you from there.