Help diagnose problem!

[Rok986]

Originally Posted by thstone

What was the thinking behind the use of the gas additive? Was there a poor running condition that you were trying to address?

No, it was running fine, as far as I could tell at least. Did it for preventative maint, but may have caused problem.

Funny thing happened this morning though. Didn't drive the car all weekend, then tried firing it up this morning and it started and ran fine! Idling normally, no misfires, so I drove it to work. Noticed it started misfiring on idle again once engine was warmed up. This is getting me more confused now. Why would the problem go away when cold, but come back when warm?

[specboxCO]

Almost definitely going to be a vacuum leak somewhere. If you have a vacuum gauge, put it on the manifold and pull off the AOS hose, if the vacuum doesn't drop much, you probably already have a leak.

[specboxCO]

Follow this flow chart to identify the issue.