Misfiring and codes P0302 and P0300

W I LLI AM

MEMBER
1999 TOYOTA COROLLA
1.8L
4 CYL
2WD
AUTOMATIC
214,000 MILES

My car's engine is misfiring I get codes P0302 and P0300 usually at the same time. Really rough idle where it vibrates in the cab.
I changed spark plugs and spark plug wires and the airflow sensor and it ran better for a while where it would only give check engine once a week. Now it's every single day at least once it triggers check engine light, usually when accelerating. I took it to a shop and they couldn't find the problem but said the fuel pressure is okay and told me maybe its the fuel injectors not working properly.

What should I do?

1 Reply

ASEMASTER6371

MECHANIC
52,797 POSTS

Good morning,

The first thing I would do is check the compression to be sure the engine is working good internally.

https://www.2carpros.com/articles/how-to-test-engine-compression

https://www.2carpros.com/articles/engine-misfires-or-runs-rough

If the fuel pressure is good, then we need to check for codes. Can you give me all the codes that were listed?

https://www.2carpros.com/articles/how-to-replace-a-fuel-injector

You could try swapping the injector around for number 2 to another cylinder to see if the misfire goes to another cylinder. That will confirm the injector being the issue.

https://www.2carpros.com/articles/how-to-test-a-fuel-injector

Roy