Car won't idle after battery change

Won't idle after battery change... SOLVED! well, for me anyway. :)

I just experienced the same problem on my 2002 tundra last night, and fixed it this morning after sleeping on the problem. Here's how it went.
I cleaned the terminals, etc., and replaced the battery, as it was 7yo and old and on the verge of failing.
Immediately after this, the truck would start right up but the idle would drop to about 100 RPM, then slower and slower, and eventually stall. Every time.
I warmed it up and drove around the neighborhood for about 45 minutes, thinking the computer needed to re-learn it's Idle settings, etc... No change.
This morning, I decided to go after the cheap and easy fixes first...
Inspect throttle body... it was filthy full of black sticky dirty/sludgy stuff. I cleaned it off using a rag and some brake cleaner. DID NOT spray brake cleaner IN the opening; just on the rag and then wiped all of the gunk out of the opening, butterfly, and inside as far as my fingers would reach with the butterfly open.
Reassembled everything, started truck... runs perfectly.

Dead battery? Won't run? Dirty throttle body? How do these all tie together?! Here's why (to the best of my understanding).
Over the past 65k miles, dirt and gunk slowly but surely builds up in the throttle body. At some point, the computer senses that this affects the air/fuel mixture or something of this nature. The computer compensates for this, and stores it to it's memory. Sometime during the vehicles lifetime, the battery fails or is disconnected. The compensation settings that the computer stored are lost when the power is disconnected, so the next time the engine is started it's telling everything to behave as default... but the car isn't in a default state, there's **** in the throttle body... or a bad sensor, etc.
I could be way off, but my gut feeling is that this is correct. My advice: Pull the intake tube off the front of the engine and clean the gunk out of the throttle body. It should be the first thing to try, since it's the cheapest and easiest thing that I can think of.

Very simple. Turn the ignition key on without starting the engine, wait about 5 minutes for the computer to learn the gas idle position. Start the enging it will idle again.
David

This is just to vouch for the solution posted by travisray. I have a 2000 Toyota Land Cruiser which had a bad O2 sensor. After replacing it, I disconnected the battery to clear the code, after which it wouldn't idle. I found travisray's post here, tried it and it worked; I've since found several similar responses elsewhere on the Web for a broad range of Toyotas. To clean the throttle body, I just used gasoline and paper towels, being careful not to leave bits of paper towel behind. Both the cause (battery) and the solution (cleaning) still leave me a bit baffled so this is just to help the next guy who can't understand why his car won't idle when all he did was change the battery...

Hello this is Andrew, you may have to replace the throttle body sensor or clean it with throttle body cleaner . do not use to much , spray the flap and start the car and let it run you may have to repeat the process two or three times good luck.