2006 tacoma, when reconnecting battery, truck idles rough, why

hi, i have an 06 racoma 4.0l, anytime i disconnect the battery for any reason, when reconnected and started the engine runs rough, idle loopy like its going to stall out. why is that

 

Probably a dirty throttle body.
When you disconnect the battery the PCM loses all learned values including learned idle and fuel trims, it takes it awhile to relearn everything especially if things are dirty.

 

Always throttle bodies. They gum up and the ecu can’t learn the state of health quickly enough so you get a low idle.

also when you reconnect the battery, leave the key on for 10 second then start it. It gives the system a chance to find throttle position and a better chance at a good idle.

it’s time for a clean!

 

Thank you for the advice. I will keep that in mind and clean it out asap.

 

two different things...

a dirty throttle body can lead to a bad idle.....

disconnecting the battery will erase computer data and can cause a bad idle until the computer becomes self aware....



you can also have random nuttiness like me. came home friday.. all was good. sat my idle was at 400rpm. disconnected teh battery for a few hours... still bad idle... drove to the office.. idle was fine. sometimes these trucks just need a good fart

 

Yep, good clean to the throttle body and give it about 75+ miles for a full relearn. Can definitely be less but more data points are always better.

 

Welcome to TW!

 

So I cleaned throttle body really well, after a few minutes of running at idle it smoothed out. However, now I've got no throttle response.

 

Did you unhook the battery when/after you cleaned it?

 

Yes, I've tried resetting it multiple times, I tried the procedure, it idles but as soon as you press gas it almost dies out

 

Likely one of the hoses is dislodged.

One of the hoses to the valve cover or the fuel pressure regulator at the back

 

Is the electrical connector at the throttle body seated all the way?

 

Yes it's connected correctly and no hose issues. Replaced throttle body itself and still same problem. As soon as the pedal is touched the engine rpm falls on its face.

 

Did you see what code(s) you have before you started replacing things?

 

Do you have a scan tool?

 

Yes of course, the only code I have is an O2 code because the upstream one on driver side got damaged so it's missing but I have a plug in the bung.

 

So you have no throttle codes?
Never seen an electronic throttle go into failsafe (limp) mode without setting codes.
Did you have any issues prior aside from the O2?

 

Absolutely none what so ever. It all started with I ran out of fuel one night, it burned up the fuel pump. So I replaced it. Then added a few gallons of gas, when I went to start engine it started just fine, but stepped on gas pedal and got nothing. If I feather the the pedal it'll gain rpm. So drove it all the way home by feathering. Ever since, the truck will idle but step on pedal and it almost dies Everytime. Still no other codes set. Making me begin to think ecu, but I hate throwing parts at it without testing the cause first

 

Have you checked fuel pressure?
If not that would be my next step with the history your stating.

 

Sounds like a wonky TPS sensor unless there is a fuel pressure or flow issue.