Rough, low idle after removing battery

@The Traveler
Miss the guy

 

So wait. Yhe 9- volt hooked to alligator clips works to hold memory when you disconnect the battery?

 

Take it for a good long drive and see if it gets better or throws a code. It should do one or the other.

 

Before you changed the alternator and all did it idle rough? When exactly did it start idling rough? Why did you change the alternator?

 

changed alt because i had to jump the truck 3 times in a week then i jumped it a 4th time and when I unhooked it the truck instantly died and the alternator was charging SUPER low, when removed the wheel of my alt spins super hard... thats why I replaced it, it started to idle rouugh as soon as I got it going today with the junk yard alt and the bad bat, then i changed the bat and it still idled hard, BUT it starts on its own now and it is charging strong. I am going to keep an eye in it, its pretty cold down here on the east coast of NB Canada. I will also scan the truck for codes and keep you guys informed. I also forgot to mention its straight piped after the cat.

 

Clean the throttle body

 

Clean the throttle body

 

This is interesting, I noticed this the first time I disconnected my battery and does it every time as well, feels like its going to stall out, and can be hard to even get started but runs fine after several minutes or a quick drive... I get that the computer resets and all that jazz, BUT I've disconnected plenty of batteries over the years and it doesn't idle like total ass afterwards on any other car I've owned.. Wonder why the Tacoma is like this... It did freak me out the first time... Guess ill just chalk it up to normal for this vehicle..

 

*UPDATE* Taco has returned to regular idle this morning when i started it to take it to work, started strong idled at 500 RPM no stalling issues. Think the ECU just was dead so long that it needed to re learn the fuel trim and air values and stuff. All is well in the world! thanks for anyone who commented!!

 

I must be lucky. I've had the cables off my '15 Tacoma 4.0L and my wifes '14 4Runner 4.0L a couple of times for each vehicle. Reinstall cables. Start vehicles. It stumbles and dies. Restart and it runs like it did before. If any relearning was going on, I was blind to it. Both vehicles ran great after a single stall on 1st start up.

A member at t4r.org claims the ECUs in the 4R will retain it's values for up to 4 hrs. I do not know if this is indeed a fact. If so, it may explain my situation as the battery cables on my Tacoma/4R have only been off 30-45 mins.

 

Mine acts weird after disconnecting the battery too. :-/

 

Clean the throttle x2.

I clean every throttle after I disconnect batteries at work.

They collect carbon over time and cause the throttle to not entirely shut. When the battery is disconnected and reconnected, it assumes the throttle is open and needs to learn the open and closed voltages, this takes time. Because it thinks its open, the truck idles low.

You don't need throttle cleaner, just WD40 or penetrating fluid works just as good.

 

Are you talking about the back side of the throttle plate where it gets the dirtiest from the PCV system or are you simply applying a penetrant to the exterior linkage? Thanks.

I've had the ground strap off my 2nd Gen. Tacoma and 5th Gen 4R 3X each and have never experienced the problem some report. There is a slight stumble the first time I restart it - lasts a second or two - then all is as it was before.

 

I have had mine disconnected for up to months at a time. No starting issues, but for sure I agree, It does run different and idles different until the ECU re-learns.

Glad you got it figured out bro!

 

The actual blade in the throttle body is what needs cleaned, pull intake elbow off spray cleaner into it, if you can key on pedal down spray again.

 

The big problem with the vehicle engine "learning" process is that it won't re-learn without a deliberate battery disconnect / re-map / re-boot process. Apparently the electrical bit-heads that invented this tuning system don't drive. So....... if you get a bad tank of gas and it re-times and adjusts the engine to get rid of the knock, you will be stuck with the "dumbed down" computer settings until you remove the power and tell it to start over - yourself.

I took my outfit on a road trip to see my son over in Oklahoma and got some shit gas in New Mexico - that immediately wrecked the gas mileage. When I realized the problem (a couple of tanks along the way), I had to stop, pull the battery connection and stand around tapping my toe for a few minutes - then reconnect. Amazingly, after this and the relearn with a better fuel supply - she did way better.

I've worked on several machines that had to have their PLC programming reconfigured after some brilliant individual installed a poorly conceived (dumb down only) learning scheme. You have to give it the ability to methodically increment performance upward until reaching a negative, then back off and reset for a period (say until the gas gauge says you refilled the tank). Then it needs to start out re-incrementing performance upward again.

I had a GM programed Z28 (2002) - and it needed to be re-set about once a month, despite using the best gas I could find.

 

This has been covered here on TW before.

 

Every time I disconnect my battery this happens, so I think it's normal.

 

This definitely works and have seen it done , there is also a similar set up that you plug into the cig lighter that keeps enough voltage in the system during battery swaps

Last year I had auto club put a new battery in my truck . He put his jump box onto my battery terminals in such a way that even after disconnecting them the still had power so the ECU and other electronics wouldn't be affected by power loss

 

My 3g 3.5 did the same thing yesterday after I had disconnected the battery to do some wiring behind the dash. Seems fine today but the vehicle had a pretty noticable vibration when I was in gear with the foot on the brake. I'm assuming it just needed to relearn the air to fuel ratio.