Gday. Slight annoyance. 1994 WRX, start her up from cold in morning and get a slightly hunting idle, it idles up and down for a few minutes then settles down. Drive off and after a few hundred yards Check Engine light and fan come on, after another few hundred yards both go off, then both on again briefly then.. Thats it, not a peek or a problem again all day until the next morning. This will also happen if I leave it tickover for longer in the morning. Is this just an electrical niggle or is it a potentially bigger issue?. Thanks for any advice.

 

Right now, I'd say that it's a niggle. Have you tried to read a fault code using the under dash connectors yet? That will give you a clue as to which sensor you may need to look at.

It could be as simple as cleaning the MAF sensor...

You'll have to do a search for how to connect up the diagnostic connectors (green and black connectors under the steering column)
The numbers translate as follows:

-11 Crankshaft position sensor-No signal from crankshaft position sensor when starter switch is ON
-12 Starter switch-Starter switch is abnormal
-13 Camshaft position sensor-No signal from camshaft position sensor, but signal from crankshaft position sensor
-21 Engine coolant temperature sensor-Engine coolant temperature sensor signal is abnormal
-22 Knock sensor-Knock sensor signal is abnormal
-23 Mass air flow sensor-Mass air flow sensor signal is abnormal
-24 Idle air control solenoid-Idle air control solenoid valve is not functioning
-31 Throttle position sensor-Throttle position sensor signal is abnormal
-32 Oxygen sensor-Oxygen sensor is not functioning
-33 Vehicle speed sensor 2-Vehicle speed sensor 2 is not functioning
-35 Purge control solenoid valve-Purge control solenoid valve is not functioning
-42 Idle switch-Idle switch signal is abnormal
-44 Wastegate control solenoid valve-wastegate control solenoid valve is not functioning
-45 Pressure sensorPressure exchange solenoid valve 12 Pressure sensor is abnormalPressure exchange solenoid valve is not functioning
-51 Neutral position switch-neutral position switch is abnormal.(AT)

Good luck

 

Thanks very much for your time. I'll give it a go.