CHeck engine light in 90 LX
 

Hey guys, the check engine light in my 90 LX 4-cyl keeps going on for about 1minute and going off for about 5 minutes. The guy who does the free diagnostic testing at the local AUtoZone says the light has to stay on for him to read it with the device they use, but the light only comes on while I'm driving in the car. Any suggestions as to what might be causing this?

Mine does the same thing. I wouldn't worry about it. I think it has something to do with either the MAF or exhaust sensors.

Unfortunately the EEC-IV (OBD1) cars have only on-demand testing and don't store continuous codes. Usually only hard faults will show up when testing the system. Most likely there is a sensor that is temporarily going out of range, then coming back again. It's hard to pinpoint those problems since they only happen when you're driving.