How do you fix a rough Idle after oil change and a possible red-lined rpm?

Answer

If you've red-lined the engine and now it runs bad, there are two possibilities.

First, if the oil foamed it could cause the lifters to collapse and that might cause the engine to run poorly. Let the foam settle then start the engine a few hours later and the problem should take care of itself.

Second, if a valve "kissed" a piston, the valve and/or piston could be damaged. To determine if that's the problem, run a compression test. If any cylinders have zero compression, the valve or piston is probably damaged and you'll need to rebuild the engine, at least the head.

First answer by Redbeard. Last edit by Redbeard. Contributor trust: 1949 [recommend contributor]. Question popularity: 10 [recommend question]