SOLVED! Trailblazer running Horrible after alternator replacement

[BillVear]

I need your Help! My mechanic replaced my alternator in my 2005 Trailblazer, and in the process, removed the Battery as well. It started fine, ran smooth as normal until I drove off. Its been sputtering, idling rough, and even stalling which it has never done before. I've heard there is a process, when to start it the 1st time after removing the battery to "reprogram" the computer to get the idle correct?

Thank you,

Bill

 

[linneje]

Often this happens with the I6 when you disconnect the battery. Try cleaning the throttle body thoroughly, then try running again.

 

[Mooseman]

Clean the throttle body.

How to clean your throttle body

 

[Mektek]

The process is to let it complete the relearn process. That means when you restart it for the first time after a battery replacement don't immediately drive away. Just let it idle for a few minutes and the computer will recalibrate itself. The climate controls also need a minute to recallibrate as well.
So try disconnecting the battery for half an hour or so and then restart and let it idle for a while.

 

[Mooseman]

The process is to let it complete the relearn process. That means when you restart it for the first time after a battery replacement don't immediately drive away. Just let it idle for a few minutes and the computer will recalibrate itself. The climate controls also need a minute to recallibrate as well.
So try disconnecting the battery for half an hour or so and then restart and let it idle for a while.

After cleaning the throttle body first.

 

[TollKeeper]

So I read on the GM tech forums that they are adding a step to this, although unofficial from GM, its what a couple OEM techs are recommending.

Turn ignition on, engine off
Let it sit for 2 mins
Turn key off for no more than 30 seconds, but no less than 10 seconds
Turn key on, and start engine
Let engine idle for 2 mins
Turn key off for no more than 30 seconds, but no less than 10 seconds
Turn Key on, and start engine
Done.

Apparently this fixes a couple different headaches created when disconnecting the battery. Blend doors get calibrated correctly, ETB (Electronic throttle body) gets to go thru the motions, and a couple other active moving sensors get to calibrate.

This does not fix the gummed I6 throttle body, just the next step for once its cleaned.

 

[BillVear]

Thank you all, the throttle body was cleaned today, I did disconnected the battery as it was being cleaned, did the restart routine. It definitely ran better, but not right, did a diagnostic, getting misfires on #6 piston? Did the coil blow? It ran great before all this...I'm speechless...

 

[Blckshdw]

Try swapping the coil with another cylinder, see if the misfire follows it or not.

 

[Mektek]

A badly running engine can cause a coil to fail. Try the coil swap.

 

[BillVear]

The coil was replaced and she is running beautifully again! Thank you all for your help!

 

[linneje]

Glad you got it. I have had it happen before where one repair led to another, which then led to another, etc. It seems like it shouldn't happen, but when you disconnect a battery, it can lead to other things you might not expect.

 

[BillVear]

Thank you!