P0302 and other weird stuff happening help!

[phyrefighterjay]

Hey thanks to you all for helping me with this situation. This yaris has 300k miles on it and this is my FIRST check engine light! Here is the time line of what ive done to it. And what is happening
1. Replaced Spark plugs 15k miles ago
2. Removed and cleaned airflow sensor with airflow sensor cleaner spray.
Everything was normal...till now
3. I noticed a Minor chugging only when cold. Seemed to smooth out just fine at any rpm above 1000
4. The siren for my lights being on has been sporadic… Leading me to running the battery dead at least 2 to 3 times because I left my lights on…
5. I refilled the battery with distilled water and trickle charged it so the battery was good as verified by an apparatus at the parts store
6. While accelerating on the freeway… Check engine light came on… Motor was running just fine. I pulled off and got an analysis at an auto parts store and got code P0302… And secondary code P0304
7. I bought a coil for the second cylinder and nothing changed… The engine ran just fine but the code remained and the engine light stayed on.
I bought a coil for the second cylinder and nothing changed… The engine ran just fine but the code remained and the engine light stayed on.
8. The engine ran just fine all the way home from Orlando… But this morning I woke up to the same CEL and now a battery light. I drove it to the auto parts store. I replace the battery and replace the alternator. The battery light went away but the CEL light remained. Now the engine doesn’t even idle very well.
9. I checked all of the injectors… They all came back with 14.2 ohms of resistance.
So...I think the coils are good but I will check them with a multimeter. I think the spark plugs are good they were changed only about 15,000 miles ago. To my knowledge I think the fuel injectors are good. But the car has 300,000 miles on it so it could be anything. I’ll let you guys take it from here. Fuel filter?

[phyrefighterjay]

Oh yeah. One last symptom it fits around 2.5 on the list. The chugging would sometimes happen when decelerating from 40-50mph to a stop. The engine would chugg a bit until it until rpms at idle could kick up and get rid of it. Then everything would be fine. This would happen while it was hot or cold.

[WeeYari]

Whenever the battery has been disconnected for any length of time, the engine will idle rough. This is because the ecu needs to go through a relearning process to establish proper fuel trims. It will settle down after some uninterrupted driving, say 30 minutes or so.

[bronsin]

When checking coils for a P 300 code you just want to switch coils to test them. Don’t buy a new coil. If you’ve got a P301 put the coil from cylinder to onto the cylinder one. If it now throws a 302 code do you know that coil is bad.

I think you are right to check the injectors they could be bad especially at that mileage. But I suspect you need to do more than just check the resistance. Not sure what to do but try to find out more about it. Good luck and tell us what happens!

[phyrefighterjay]

I found the culprit it was a valve timing solenoid right above where you would tighten the alternator bolt… In other words I probably hit the sensor and broke the little plastic thing in half while I was tightening the alternator bolt… Watch out for that thing! The check engine light went off

[bronsin]

Great it’s fixed! That’s a common issue damaging the sensor when tightening the alternator belt.