Helping a friend install a new 3.4L in his toyota 4runner. Having a brain fart on how to find TDC. timing is belt is off, overhead camshaft cogs are lined up on timing marks and I turned the crank until air stopped coming out of #1 cylinder spark plug hole. I used duct tape over the hole and watched it flex like a drum skin. How do I know if this is the compression or exhaust stroke? Am I missing something simple? thanks in advance.