Yaris Misfire

[Stourbridge yaris]

Hi,

 

I hope someone can assist me with an issue I've been having with my car. Recently, I had the PCV valve and rocker cover gasket replaced because my car was misfiring and the spark plugs were covered in oil. New  Spark plus were installed and i replaced one of the coil packs. Additionally, the car was serviced with new oil and filters.

 

After driving about 1000 miles, the car started intermittently misfiring, around 3 to 4 times during a 5-mile journey. The revs are stable, but the tachometer fluctuates occasionally when in idle.

 

There are no error codes. Upon inspecting the spark plugs, I noticed they were covered in carbon, which was unexpected after only 1000 miles.

 

Can anyone recommend what I should check to identify the cause of the misfire?

 

Thanks in advance!

 

[TonyHSD]

Fuel mixture is rich and the oil leak hasn’t been fixed too. One of the plugs is oily again. For the fuel mixture you need to think on the fuel supply side and then non the air supply, both ways thorough inspection and sensors check and clean, map, maf , also on the exhaust side. Fuel mixture sensor , lambda sensor, pre and after cat. These are the things you need to look at. You can also do a throttle body clean. And double check this oil leak again. 
Good luck