2005 Lexus IS 200 P0301 error code

[alohomora]

My buddy's '05 Lexus IS 200 auto starts misfiring hard once it warms up. CEL flashes and throws P0301. Swapped plugs and coil pack on cyl 1 already, but nothing happened. Any chance this is a fuel injector or vac leak thing? Any leads would be useful.

 

[LexiLexusLux]

I think you could be on the right track.
A fuel injector is definitely a strong suspect for P0301, especially since the misfire only happens once it warms up.
They often act up more when hot.
A vacuum leak is also possible, but often those tend to be more consistent regardless of temperature, or worsen with throttle input.
A proper diagnostic tool can help pinpoint the issue with live data, but if you prefer to DIY, swapping out the injector to see if that fixes the issue is a pretty reasonable next step.

 

[LeeY0h]

If coils and plugs didnt help at all, then it's likely a bad injector or vacuum leak on cylinder 1.. Check fuel delivery and compression next

 

[alohomora]

Thank you guys for the reply. I was able to figure it out thanks to these. I mean, I just didn't have the time to reply to you all. It was at the tip of my tongue anyway.