Just got a 94 Grand Am 3.1 V6 automatic. Car runs great, and just had a used
engine put in with approx 120 000 km (75,000 miles). The engine light comes
on when I am on the highway and I drop in speed by about 10 km/h.
If I travel around in local traffic even upto 80 km/h it does not happen.
Only at or above 100, and then coast down by 10 km , the light comes on. If
I turn the car off, it is reset and the light goes off. It has the OBD1
diagnostic connector, and the garage said something about a map sensor or
possibly O2 sensor, so they replaced both of those. The problem persisted,
then I believe they said they replaced the ECM. The problem went away for 1
day then returned.
Any thoughts ?