Was running great till battery disconnected, now idles super rough

My 2010 Toyota Tacoma was running great until the battery was disconnected fora few hours and now it is idling super rough and when I come to a stop it acts like it wants to die. Any ideas?

 

Clean the throttle body and allow the idle to relearn by unhooking the battery for a few min, reconnect it, start it, and allow it to idle up to operating temp. Idle learn doesn't begin until coolant temp goes above 174F.

 

thank you i will try this

 

It didnt work

 

Also carefully clean the MAF sensor using appropriate techniques. Use a MAF-specific spray cleaner, don't physically touch any of the inner parts of the MAF sensor with anything. (No fingers, Q-tips, cloth, paper towel, etc.) Only takes about 10 minutes the first time, and 3 minutes once you know exactly what you're doing. I tend to clean this sensor about every oil change or roughly 4-5K miles.

My understanding is that if the MAF sensor is dirty it could be causing the truck to mis-read the amt. of incoming airflow and overcompensate in the wrong direction, causing excessive rich or lean and rough idling.

https://www.youtube.com/watch?v=Y9hqj0rrtQI

 

Interesting, did you get it up to operating temp (174F+).

Alot of learned values get cleared with a battery disconnect, idle is typically the one that is most noticeable especially when the throttle body is dirty so it's always my first go to for a low/unstable idle complaint and it fixes 90% of them.
If you have another underlying issue that the ECU has learned to compensate for over time it will be exaggerated when the ECU is reset.
Did you have a CEL/codes before? Do you now?

 

Did you push the throttle blade open and clean the bore with cleaner on a rag or soft bristle brush? You have to get the crud off the bore where the throttle plate sits when its closed. If its really dirty you may have to remove it completely and clean it on the bench

 

There were no codes, and yes, I let it idle for over 30 minutes, and it was at operating temperature. It still ran horrible at idle. I drove to the store about 2 miles away. It ran good until I had to stop at a light and then wanted to die, but it never did die.

 

Interesting, it should have re-learned unless it's not getting past the 174 degree threshold for some reason.
Do you have a scan tool or scangauge so you can see actual coolant temp?

 

No i do not have one

 

did you mess with any vacuum lines or anything. Why was the battery unhooked for a few hours?

 

I took the battery out of my pickup to take it to get another vehicle that had no battery and it was too late to get a battery anywhere. it was out of the truck for about 4 hours. I checked all vacuum lines and all look just fine

 

If its heavily carboned up it won't relearn properly.

Have you actually cleaned the throttle? It makes a big difference.

 

No I have not yet, headed to buy the cleaner after work
today and do that first thing when I get home

 

Thank you all for your help. My truck is now idling perfectly again. You all did a great job. Thank You all again.

 

So, what were the steps and procedures you used that fixed it?

Which of the above suggestions, or did you do them all?

 

Just idling will not get it to re-learn everything that was lost by disconnecting the battery. You just need to drive the car for 10-50 miles and it'll re-learn where everything needs to be for your engine to work correctly. Cleaning the throttle body is a good idea as it'll get rid of any built up gunk in there but it is not necessary for the ECU re-learn procedure.

 

Yea not everything re-learns at idle but idle is typically the most noticeable thing after a battery disconnect especially with a dirty throttle body and it will only learn while idling at operating temp.
If the throttle body is really dirty though it may not learn at all or take forever to learn so cleaning the throttle body is always my first step for a poor idle complaint.