Question about 2004 Ford F150

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Computer was unpluged and battery was disconnected and now it won't idle.

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Sounds like your computer needs to relearn it's idle. What you should do is disconnect the negative battery cable for a minute or so. Reconnect it. Star vehicle but DO NOT drive it. Let it idle if it will for 10 minutes (you may need to help it but don't gun the engine just hold it steady and not at a high idle) then turn the air conditioner on for a few minutes. Now drive the vehicle for about ten minutes and that should clear it up. There is a couple of other things that could be wrong such as; did you unplug or plug the computer in when the battery was still connected ? If this is the case you may have bigger problems but may be something as simple as a fuse if this is the case. Try the relearn procedure first. If that doesn't work reply to this solution and i should recieve an email letting me know you replied or you can email me at with any questions and I will see if i can help you. Remember to tell me your make model and year if you email me. Anyway I hope the relearn works for you and good luck....

Posted on Mar 19, 2011


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Code p0506 subaru after disconnecting battery

Often when disconnecting the battery the engine control computer 'forgets' the existing parameters for idle speed and such. The DTC that you are showing indicates that the idle speed is lower than expected. I have found that erasing the code with an OBD reader and then putting about 25 miles or so on the car will correct the low idle as that allows the engine control computer to bring the operating parameters up to date again as they were before you removed the battery.

Jan 17, 2013 | 2007 Subaru Legacy 2.5i SE Sedan

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Sometimes it won't start

Sounds like you may have a starter motor going bad. When they start doing this it is because there is a "bad spot" on the motor armature. It will continue to work each time until by chance, it just happens to stop in that same place again. Usually, it gets worse over time where it starts happening more and more often as more bad spots start to develop on the armature. Then eventually, it gets to where it won't work at all. Disconnecting the battery is probably not doing anything to help you get it started, That is probably just coincidence.

I also would not recommend continuing to disconnect the battery. If there is something else wrong (not the starter motor), it is probably setting a code in the computer. Disconnecting the battery can clear the computer memory and cause this vital information to be lost. You will need this information if you are going to figure out what is going on.

Also, every time you disconnect your battery, your adaptive fuel trim, idle control, and adaptive transmission shift information gets lost. Then when you reconnect the battery, the vehicle can waste a lot of fuel and cause undue wear on your transmission clutches for a few days until it "relearns" this information.

This also causes undue stress and wear on your battery cables that can lead to more serious electrical system problems.

This also causes all of your computer modules to go through a "forced re-boot" every time you do that....anybody that has much experience with a PC at home knows that the best way to destroy a hard drive is to unplug the computer from the wall without properly shutting down then pluging back in again. Files get lost and/or corrupted. If the boot files get corrupted the computer will not reboot at all. Car computers are no different.

Repeatedly disconnecting the battery is just not a good idea.

Feb 15, 2012 | 2000 Mazda MPV

1 Answer

When let off gas idle drops down and stalls. Ok at first when cold idle on but once warm stalls when let off gas. Problem started after removed battery terminals to clean with baking soda.

Not too sure about Toyota's but sounds like the computer has "forgotten how to idle". Fords do this when the battery is disconnected, as did some Cadillac's. Ford's solution is to let it idle for 15 minutes to "re-learn" operational characteristics of the engine. Found the following elsewhere:
Disconnecting the battery (for longer than a few moments) causes the onboard Engine Control Computer to reset and forget all the calibration data for your car. (In much the same way that you might have to re-program your favorite radio station push-buttons again.)

When you re-connect the battery and re-start the car, it has to "re-learn" all the correct settings for your particular car's engine all over again and the only way that happens is by actually using the car. Taking the car to the dealer as someone else suggested won't do any good, unless you like paying $65+ per hour for the mechanic to drive your car around and get it all warmed up. :-)

After about the first 10 miles, the idle will be much better. It will take 30-50 miles for the entire re-calibraton to finish. Take a 25 mile interstate road trip one way, turn around and come back home.

Jan 15, 2012 | 2003 Toyota Camry

1 Answer

I changed the battery on a 99 Ford Escort and now it starts but will not keep running (will not idle),

Check make sure nothing has been unplugged while the battery was put in..If it all looks ok drive it alittle bit,,sometimes the computer needs to relearn after the battery has been disconnected..

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I have a 2004 pontiac sunfire with a few problems. First, when I turn the ignition to start the car all I get is a fast-paced clicking sound from the dash area and the engine doesnt even turn over. This...

as fo the idle, there is a IAC ( idle air control to maintain idle. you may have to remove this and clean the carbon out of it, and the intake as well. as for the clicking there are 3 solutions to fix it. battery if it is ok, the solinoid is bad on starter or the starter itself. but it does sound like a bad starter solinoid, because a bad battery will make the same clicking from solinoid. but make sure battery is ok first. when engine is off voltage at battery should be at least 12.6 or better. when running and alternator is ok, it should read about 14.2 to 14.7 if lower then 14 volts alt. is bad. have a very good day !! hope this helps!

Jul 09, 2011 | 2004 Pontiac Sunfire

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Stalls when at idle after changing battery

When you changed the battery the computer must re-learn the setting again. If it continues have a OBD II reader plugged in and check for codes.

Feb 01, 2010 | 2003 Mitsubishi Eclipse Coupe

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Rough idle

sound slike you may have unplugged or disconnected somethine else or the spark plug you put in is bad or inpropper gap

Sep 03, 2009 | 2002 GMC Envoy

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Battery chaged and car DOES NOT idle

when u disconnected the battery u lost the adaptive idle learn program, do the following to clean the intake and allow normal idle

Here are some of the causes of surges, stalls at stops, slow idle speed, erratic idle speed, rough idle and engine hesitation (and other problems), it is in most cases the idle speed control air-bypass valve and or throttle valve and upper intake, these area's get full of gunk and combustion residue over the miles and cause idle issues (stalls, low idle) like yours, Get a can of intake cleaner from any local parts store, not carb spray, intake cleaner, it is made by a company called CRC, remove the air intake hose to the engine, hold the idle high so the engine won't stall, then spray the can of cleaner into the intake while keeping the engine running, use at least 1/2 the can, shut down the engine and disconnect the battery for 5 minutes, then restart and complete a number of mixed driving cycles, town, freeway, stop and go etc., after a few days the problem will go away as the system will relearn to the clean intake.

May 03, 2009 | 2001 Mitsubishi Montero Sport 4WD

1 Answer

2002 vw 5 speed Golf intermittently running hot for 2 months

the computer is reset when the battery is disconnected, it takes a few days to relearn your driving habits for idle strategy only, it would have not affect on the cooling system of any kind. check and verify the engine cooling fan is running, if u have AC turn it on, this will cool the engine down and should engage the fan. Make sure that no connectors near the battery were left unplugged or accidentally unplugged.

Apr 15, 2009 | 2002 Volkswagen Golf

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