Issues running after reconnecting battery

I have a 1998 tacoma 2.7. When I start it up after disconnecting battery it barely wants to run but then it evens out and when I push it to full throttle it doesn't act like it should Really low power. Has troubles getting up to 65

 

Wen was the last time you cleaned you MAF sensor? Sounds like your ECU is thinking your air inflow is very low, thus restricting fuel.

 

Happened after you disconnect the battery? Clean up the battery terminal(s). You have a 20 YO vehicle, also check the grounds.

 

What's the maintenance history on this thing? Why are you disconnecting the battery? Does it eventually return to "normal"?

Have you tried connecting an OBDII scanner to it to check for error codes?

But, if the maintenance history is unknown, you should be doing the "normal" stuff anyway, like plugs wires, cleaning the MAF, IAC, throttle body, etc...

 

Totally normal, when you disconnect the battery, you clear the fuel trim tables. When you reconnect the battery and start the engine, the ecm starts learning the fuel trims and everything goes back to normal.

 

Agreed. Just keep driving it and monitor its performance. It should gradually improve after each key cycle, just takes time.

 

I wouldn't go that far. While the ECM does "reset" when the battery is unplugged, the "stock" values shouldn't be that far off. If those values get reset and it runs like shit, that's a sign there's something wrong that the ECM is having to "learn" to compensate for.

When I plugged my battery back in after a weekend of doing my timing belt, it purred like a kitten the instant it started. I've had the battery unplugged numerous times while welding or just letting it sit for a few weeks, and not once has it run like shit when I started it. All the evap codes are "not ready" but there's no noticeable difference in driveability.

 

Incorrect. The values are wiped out to Zero ( 0 ) and only repopulated after the engine and Bank 1 sensor 1 is heated to the proper temp to go into closed loop.

 

cool.

 

Clean the throttle body.