underwoodiii Posted December 12, 2009 Share Posted December 12, 2009 My 96 2.2 Legacy Wagon hit about 130,000 miles and I noticed the fuel mileage slowly went from 31 to 23 over the next couple of weeks. The "check engine" light came on after that but the engine continued to idle just fine and ran fine on the freeway. I changed the Coolant Temperature Sensor and cleaned the MAF Sensor tonight (disconnected the battery to reset check engine light) and then took it for a spin and when I got home the radiators cooling fans would not kick off. They thought it was the middle of the summer. It's about 15 degrees out so that is a bit confusing to me. The check engine light did not come back on and the engine sounds fine. I guess I'll take it for a longer drive for a mileage check. Does any one have any idea about the mileage and fan issue. Any help would be appreciated. Link to comment Share on other sites More sharing options...
ehsnils Posted December 12, 2009 Share Posted December 12, 2009 And you didn't read the codes? It's always a good idea to read the codes - they may provide information to the problem. Cooling fans running can be an indication of several things - all from that the ECU thinks that the AC is running to a broken ECU that has turned into limp mode. Link to comment Share on other sites More sharing options...
Platinum_Racing Posted December 12, 2009 Share Posted December 12, 2009 My car did this for a while but the temp sensor appeared to be fine, as the temp gauge in the dashboard was still reading accurately. I was told this can be a sort of "Safe Mode". If the engine doesn't know the temperature of the coolant it will leave the fans on just in case. This didn't explain why my 92 was leaving the fans on all the time, but I didn't get a check engine light at all. It was winter so I just unplugged one of the fans. Since then the problem has gone away on it's own, and I never found any rhyme or reason for it. This doesn't explain the loss of gas mileage. It could be a faulty O2 sensor, but those tend to degrade over time and give faulty readings. It could be O2 sensors that are causing the ECU to run the engine blindly, or a faulty ECU itself, as ehsnils posted above. Link to comment Share on other sites More sharing options...
Stang70Fastback Posted December 13, 2009 Share Posted December 13, 2009 Is the gauge on the dash even connected to the thermostat? I once had an issue with my car revving wildly (like up to 4k) on it's own. Had to put it in neutral when coming to a stop or I'd have to have my foot firmly on the brake. People always thought I wanted to race them lol. Made me speed unintentionally on back roads cause it would pull a bit and so I'd realize I was going 10 mph faster than I was expecting. Anyway turned out the thermostat was faulty and giving RIDICULOUSLY cold readings to the ECU which was revving up the engine to try and warm it up. Never saw any sign of anything wrong with the gauge on the dash until I let it sit for a few minutes one day and it ACTUALLY started overheating cause the fans didn't come on (since it thought the engine was cold) and THEN it actually showed on the dash. So just cause the temp looks normal on the dash doesn't necessarily mean the thermostat is working properly. The fact that his fans stayed on makes me think his issue is the opposite, and that his thermostat is giving incorrect HOT readings. Dunno if that would explain the loss in mileage though... Link to comment Share on other sites More sharing options...
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