I have had bad battery since i got my ZJ, i didnt think it was bad since the green checkpoint was green and the voltage was 12+ the times i did messure it. But the car has been a litle hard to start, its like it didnt get any power to the starter but i did think it should be like that. Yesterday i needed to get power from another car to start, then i notice that the starter did run much faster. Today i replaced the battery and the car has a totaly different startup. Could a bad battery cause the engine to run lean?

 

No

 

okey, so when the PCM is in learning mode its running rich?

 

Your problem has nothing to do with fuel. It was the battery. a bad battery can have 12v. starting the engine can put over 200 amps load on your battery which can make it go below 9.6v(which is the suggested replacment margin when loaded at half of the cca rating of the battery beimg tested). But ive seen cars barely start because it dropped as low as 7.5v. This voltage drop can affect everything electical used upon startup. Its also bad to have an alternator charging a junk battery since it can burn it out because of the voltage fluctuations. Ive got the best battery on the market and that baby throws that engine into motion 10 harder!

 

I know that, but since my engine has been running lean (color on the exhaust valve) but there isnt any error codes, i tought that maybe the computer was reset when the voltage drop when i try to start the engine. I do have a new oxygen sensor, but i didnt manage to get the old one out so i havent replaced it. But i did replace the intake temperatur sensor so i will see how it goes.