I installed a new alternator. The next day the car would not start. I checked the pigtail the three pin connector to the alternator and it was corroded and pretty much turned to dust in my hand so I went to the dealership bought a new plastic plugin put the three plungers in. but instead of red green white I put green red white and forgot to disconnect the battery. When I started the car I heard a pop. I corrected the wiring. Now every time I start the car I get all the misfire codes as soon as the car gets to operating temperature it will start up run perfectly for about 20 minutes and then the lights will turn on and then the engine will feel like it's going to stall. If anybody has any experience with this I could use somebody's help I don't want to go spend thousands of dollars I think I might have blew the ignition control relay. But I'm not sure this problem literally happened the moment I reconnect the battery started the car and heard the pop. the car was literally 100% before only reason I change the alternator is because the bearing went and I was hearing squeaking. I just put a new alternator in the car today. returned it with the warranty they gave me a new one the last one was pulling 16 volts for some reason I don't know if it was because of what I did. If anyone has any ideas or previous experience with this problem I don't know if anybody was dumb enough to mess with the alternator without hooking the battery but if you did I could use some insight thank you very much

 

What are the exact codes?

Check ALL fuses and report back.

 

The the codes are just the po300 misfire codes. And a crankshaft positioner codes. This problem start literally 20 minutes after I started the car and heard the pop I know I blew a relay or something. All the fuses are fine tomorrow I'm going to swap out the PCU relay. And the ignition control relay which I believe the fuse box behind the change drawer inside the car is a two-sided fuse box so I have to figure out how to get behind it which I have not figured out yet. I just swapped the alternator yesterday. in case something popped inside of the alternator or the alternator is causing me the problem. I haven't drove it yet while I was replacing the alternator again I noticed the coolant reservoir was bone dry.

 

You may have damaged the body ECU or even the engine computer, the regulator in the alternator is tied into several systems. Hopefully you just fried a relay or two.

 

I don't know if the computer is fine or not but it throws off the codes after 20 minutes a half hour I will drive the car it will start up perfectly drive like a brand new car literally and then about 15 to 20 mi later all of a sudden I get to check engine light come on and then 5 seconds later after that it starts blinking and then the car runs like really rough idle sounds like a long one getting ready to run out of gas I have a full gas tank. and might I remind you that none of this happened until I discovered the clip to the alternator was corroded and I heard a pop. Do these es300s have a alternator fuse? Told me to come see and would the car even start if a feasible link is blown.

 

And and do these Lexus ES300 even have fusible links lynx even coming from the alternator

 

Everything on the car is fused except the starter.

 

Do you really think I blew the pcu because it is still throwing off codes and I'm able to turn them off. I know the thing that happened today I drove to the store real fast and whenever I went to start the car it started acting up immediately and as soon as I hooked the computer up shut the lights off boom was acting like a brand new car again. Which relay should I be looking to change I already changed the PCU relay

 

I started up the car again the alternator did not fix the problem the new alternator remember I put a brand new one in something pop because I forgot to disconnect the battery and put the three wires in wrong replace it again like I was saying I drove it today as soon as I started it it started acting up RPM's going up and down up and down check engine light flashing and as soon as I reset the code turn the car off restarted it it drove fine for another half hour and then started all over again lights came on again engine started stuttering RPM fluctuating up and down up and down. And I got five misfire codes codes. so what you were saying is that model car probably does not have a fusible link. Which relays exactly do you think I might have blown. I do not hear any clicking relays. Like I said it drives like a brand new car until 20 minutes later all this stuff starts happening again. I'll have to sit somewhere for an hour let the car cool down and remember it does not overheat. Person I have never met the temperature gauge never goes past the center. So it's not an overheating problem I checked all the fluids I checked all the oil. It has to be some kind of relay what relays are connected to the alternator that could possibly blow? I'm a contractor man I could build a house from top to bottom but when it comes to cars I don't have a clue bro

 

Oh oh and I also changed the CPU relay.I did not change the ignition control module relay because the fuse box inside the car apparently has two sides and I do not know how to get it out to get the backside.if I took it to the dealership would they easily be able to figure it out or are they going to charge me $130 an hour * 10 to figure out something that is pretty easy for them to figure out

 

It almost sounds like your battery is shorted. Don't go and buy a new one, but maybe borrow one from your wife's car or something.