So the last couple of days the battery has been on its last legs, I had it checked and it was a gonner. I replaced the battery, but when I started the engine and started to drive away, as soon as I let up on the gas pedal it dies.
Its as if the damn thing forgot how to idle. It runs great otherwise. I am able to drive it as long as I break with my left foot and keep just enough on the gas pedal to keep it at idle speed, otherwise it dies. It will start right up just fine. When it is cold it idles ok. I can drive it for a few minutes without have to hold the pedal, until ti warms up, then I have to hold the pedal. It worked great until battery change. I am thinking something went screwy in the memory of computer on how to idle, but I dont know where to start. It did throw a n engine check light this afternoon. I have yet to get that code pulled.

 

Do you have access to a scanner ? Knowing what codes are present
or pending would help. You also need to see what the alt is putting out.
It may of killed it and it's only working when it's cool or running
at higher RPMs. So get your DMM out and check the voltage
while it warming up and see if it drops just before it dies.

Sean

 

hey, i dont know if you have a gasser or diesel.

My truck does the same thing. 2 yrs ago I changed the battery and the EXACT same thing happened. It took about 2 weeks of stalling for the truck to figure itself out. After a couple weeks it was back to normal.

Then I did the spark plugs a couple months ago, and disconnected the battery. It did the EXACT same thing again. It took a couple weeks again to get remember.

The worst was when you slightly tap the gas and abruptly let off. A guaranteed stall.

My theory is the gas pedal sensor is f'Ed up somehow, and the computer need some time to adjust. I did a little research 2 yrs ago came to that conclusion. I decided to try to let the truck sort it out itself, and it did.


Hope that makes you feel better.


My suggestion it to not drive with 2 feet. You have to let it try to idle and stall. That seems to be when it makes the adjustments. If you 2 foot drive, it is never going to relearn the idle trim and strategy (of course when you are at a busy intersection, all bets are off)



At least that's my $.02

Good luck

 

I replaced the battery in another brand of vehicle, and it took a couple of weeks before it idled correctly. I suppose that the computer has to reset itself.

 

The codes could help a lot, could be a bad TPS and the computer is trying to tell you with the CEL. In the mean time I would check and make sure your grounds are good. Sounds like you have a Gasser, if so check out the condition of the MAF senso and throttle body for carbon/dirty.

 

It may of killed it and it's only working when it's cool or running

 

Many PCMs have to undergo a "relearning" procedure after they have been installed or if they have been disconnected from the battery. On some newer vehicles, a scan tool may be required to reprogram the PCM and to reset the anti-theft system. On some applications, there may be a specific relearn procedure for establishing the base idle speed and other operating parameters. On others, it may be necessary to take the vehicle for a short test drive so the computer can adjust itself. The exact requirements will be spelled out in the vehicle service manual. The best advice here is to test drive the vehicle after the powertrain control module has been installed. A short drive cycle that includes going over 35 mph will usually reset most PCMs so they will operate properly. The powertrain control module will also continue to learn and make small adjustments to the fuel mixture and other functions over time as the vehicle accumulates miles.

Ford Motor Company Driving Cycle

 

Thanks for all the advice, It is gas. I don't think the alternator is dead, I am inclined to go with the needing to relearn. I read somewhere that removing the battery sends the computer back to default settings, and if it has learned to compensate for dirty maf, and other things that would cause performance problems, then it needs to relearn them, or I need to do to maintenance on the maf, o2 etc.

 

If the battery is disconnected, the engine has to relearn how to idle. Start the engine and let it idle for about 5 minutes.

Your transmission will also need a relearn cycle.

 

For whatever reason, the fly-by-wire gassers do this when the battery is disconnected.

Many people, at least those with V10s, found that cleaning the MAF makes it all better. It's worth a try.

The theory is that over time, the computer deals with the MAF getting dirtier and dirtier. But by resetting it, it forgets what it's learned and has a hard time dealing with the suddenly different MAF readings.

There is also a recalibration process for the fly-by-wire throttle, it's around on the site somewhere...

 

I've never had this problem with my FBW system.

 

Especially after unhooking my battery/resetting PCM. I may be one out of the bunch but I think their is another cause.

 

On my escape when the battery was disconnected to clean my posts I looked in my haynes manual. It stated for the computer to relearn that I had to idle for 1 minute then idle another minute with the air conditioner on, then drive the escape for 10 miles to reset, unreal but worked fine.