Hey guys. New here and had a quick question. I'm familiar with cars, but not so familiar with 4runners and their quirks. I just got my codes pulled at Autozone and I got the following ones:

P0303 - Cylinder 3 misfire
P0440 - Evap system small leak/ no airflow
P0133 - Heated oxygen sensor, bank 1 Sensor 1 circuit slow response (O2 sensor)
P0130 - Heated oxygen sensor, bank 1 sensor 1 circuit malfunction (same O2 sensor)

The engine is definitely misfiring pretty badly, to the point where I thought my transmission was slipping. I should also note that I ran without a gas cap for a few weeks about a month ago so I'm hoping P0440 is related to that.

My question is, do you think the O2 sensor errors could be causing all of this? I'd really prefer not to hunt down a vacuum leak or have to replace the EVAP system. Is it possible the code for the evap system is left over from the missing gas cap? The check engine light was on until I put in a new one and then it went away. I'm just wondering if the computer didn't store that error from before. I know the O2 can cause misfires so I'm fairly confident those two are related.

Thanks!

Oh, almost forgot, 1997 3.4 V6 Automatic.

 

I am having the same problem. Mine is a 2000 3.4. I am going to change out the coils this weekend to see if I can make the code jump to a different cylinder.

As to your P0440 code, reset the codes and see if it comes back. If it does come back, you will know it was not the gas cap.

 

So this morning, I swapped out Coil 3 with coil 1. Reset the codes and ran the engine. Still rough running with a misfire in cylinder #3. Swapped out coil 3 with coil 6. Reset the codes and ran the engine. Rough running with a misfire in cylinder #3. Replaced injector for the #3 cylinder. Seems to have fixed the problem.

 

The evap code is likely from the gas cap. Sounds like your o2 senser is ready to be replaced tho. I it was , bank 1 sensor 1 lean condition... id say vacuum leak, or stuck/dead injector.
Sounds like you figured out the misfire on 3 tho....

How many miles on thhe truck?

 

I have 214000 on my 2000 4 runner. It's not the one in my picture. The one in my picture is an 86 with less than 200000 miles on it.