Would there be much benefit in resetting the car's computer (mine is '95 obd 1 subaru)? I just got back to pdx oregon, from california, and the weather has gotten much much colder recently; real pacific nw winter weather. Anyways, I think the last time I reset my car's computer was in the summer. Would it make any sense to do this now-- due to the different temp's and the winter fuel?
2nd question: my milage has dropped about 10%, now at 25.5 mpg to 26.3 mpg these recent 2 tanks with 2/3 or more hwy. In the summer and much of the fall it's 27.5 to 29.5.
No, it makes no sense in resetting your ECU. Every standard, normal ECU as mounted OEM in a vehicle can handle any type of weather.
And even than, 'resetting' an ECU just erases troublecodes, idle learning needs to start all over etc... But there's no influence at all on weather or fuel economy.
Fuel consumption does go up in winter time. 10% seams normal to me.
There is absolutely zero reason to reset the ECU for weather changes. It has an intake air temp sensor and Engine coolant temp sensor so that it knows what's going on so it calculates how much fuel you need as it goes. As mentioned, if you reset it all you do is make it have to re-learn fuel trims (which aren't affected by temp anyway) and re-start any emissions tests.
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1990 Toyota Cressida 7M-GE 3.0 I6/5-speed manual
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The computer will make adjustments on it's own depending on the conditions it's being operated in. The feedback from the different sensors does all the work for you. Resetting the ECU will cause it to lose all stored memory probably causing you to use more gas until it relearns everything. I know on my '88 Escort which is also OBDI when the battery is disconnected while working on something in the electical system or for battery replacement when the car is first started back up the engine will rev to what sounds like about 3-4K rpm and gradually goes back down over a period of the next 5 minutes or so. Even OBDII systems will usually take 50-100 miles and sometimes even longer to relearn everything and confirm all systems are ready for emmisions testing. That's why if you have a check engine light you can't just disconnect the battery turn the light off and go for an emmisions test. The emmisions testing equipment will tell them whether all systems are ready for inspection or not.