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Some guy told me the other day that if you leave a computer controlled vehicle without a battery for some length of time that it will have problems when replugged back in. Interestingly enough, my friend has a 3-VZE that did not have a battery for a year while it sat. Get a battery plugged back in, start it up, thing runs like crap. Sure, could be a gas problem but this thing runs beyond just having a little varnished gas. And it ran perfect when he parked it! Now I don't know if the computer could have anything to do with it, but I would like to narrow down the possibilities so he can get back on the road. Anybody have an experience with this? I personally think the guy that told me this is full of it becuase the functionality of the EFI is burned into the computer and thus can never be taken away, but is there perhaps some things that the computer could "forget" that would affect the motor's performance?
 

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i wouldnt think the computer would have anything to do with it. i would search elsewhere for your problem.
 

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If it sat for a year and you started it on the gas that was in the tank that is one of the problems. Modern gas goes bad fairly quick. Get 5 Gallons of fresh and dump it in the tank. The computer start reprogramming itself as soon as you hooked up the battery:D
 

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Actually, depending on the year some comuters do learn. They have a set map they use as a starting point,but they also have the capability to learn and store "driving habits" as we called it.

It retains this in flash memory like pc ,but like a pc if the backup battery goes dead then you need to reconfigure bios.

The ecu will just go back to stock mapping ,which will not make it run that bad. My guess would be fuel contamination and possible injectors being clogged. Maybe even plugg wires have been eaten by mice or field rats.

But in no way what so ever will unplugging the ecu cause any vehicle not to start up again one it is reinstalled. In most cars you will not notice any difference,if that were the case how could we possibly replace batteries and alternators. Just not true.

We do see learning curves start from scratch and the mpg meters in the trip computers and onboard displays go back to a base mpg reading ,like from 18mpg to 15mpg until it runs a tank or 2 through it. That and fuel economy may be affected ,by relearning the octane and ping signals from both knock sensors and o2 sensors and air temp ,and all the other sensors.

We saw this with what we called winter gas out here in Ca in 90-91 when peoples fuel mileage went doen from 21 around town in a LS400 Lexus to 15mpg. That was caused by the alcohol and the MTB's put in the gas to make it oxygenated. Which in a older car without o2 sensors fore and aft of the convertors and the ecu controlling cylinder like we have in some cars would make it run cleaner and hotter when cold. But in these high end cars it made the ecu think it was runing to lean, which made it richen it up .that ate up gas like crazy,so how did we save the enviroment by using more gas and putting more pollutants into the air...
we didnt... but i aint on the Air Resources Board for that arguement.
In short i beleive the ecu isnt the problem in your friends case,chek the basics first fuel and spark .Run some fuel system cleaner through it and change the plugs if need be.


Good luck
GGary
:eek:
 

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The probability of something bad happening with no battery hooked up is less than with one hooked up. The "Some Guy" is presuming a capacitor or rechargable battery has to keep charged up in order to keep the program. I'm not sure what device is used in the Toyota computers but I would think they would use something more permanent, after all people stopped using rechargable batteries and capacitor rows in the 70's in small memory devices. I would think as soon as it gets power it loads the baseline program, perhaps it was tweaked before and the timing or a sensor needs to be reset.

I would look elsewhere before I start looking at the computer, like you said, new gas, check the timing and a good blow out drive on the freeway.
 

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I had this happen on my Chrysler a couple of times. It cleared up in about 30-60 seconds.
 

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HAHAHAHA

You're posting in the wrong board. This board is for SAS questions. You need to find the IFS board where people aren't carb'd.

Yes, the ECM's have eraseable learn tables in addition to their ROM program. Sometimes reseting the computer will also clear damaged tables that can cause the engine to run poorly. Look to the gas like what was previously stated, but you can always try another reset by pulling the ECM fuse for a couple of minutes. Trouble codes get cleared this way as well. The "empty" tables could have gotten corrupted when you hooked up the battery.
 
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