2000 Corolla - Rough Idle, Misfire - Data Capture Included

[superkevster]

Hey everyone,

I'm hoping for some help diagnosing an issue I've been having. This issue occurs after the car has been sitting overnight. Seems to be worse if its colder out, but I'm not 100% sure about this. The car cranks to life just fine, but runs very rough. A few times it has actually completely died. But it always starts right back up. Any pressure on the accelerator and the roughness pretty much disappears.

I'm thinking maybe IAC valve? But I really don't have much of a clue. I thought maybe vacuum leak, but from what I'd gathered, I'd expect positive short term fuel trim at idle and didn't see it.

I checked spark plugs. They looked ok to my untrained eye. MAF looked clean too.
Photos of spark plugs and data captured from torque attached. If I should capture a specific data from a specific drive cycle, just let me know.

Thanks for your input!

View attachment 20150117_112839.jpg

View attachment torqueTrackLog.zip

 

[Scott O'Kashan]

Is the check engine light on?

How many miles are on the vehicle?

 

[superkevster]

~140,000 miles
Engine light is on, code P0300, random misfire.

 

[shawn99corolla]

Does the car stop misfiring once the engine is at operating temperature? In other words does it only misfire when cold?

 

[superkevster]

Yes, it only misfires when cold I believe. It is only when the engine is cold that I can feel it running rough.