I had some oh-so-wonderful hesitation and an exhaust backfire this morning. The car wasn't really up to temp - it had been running for about 15 minutes and it's ~68F this morning.
Some potential causes I've found are:
- Sticking exhaust valve
- Running way, way too rich, somehow getting ignition in the exhaust. Note that I have NOT installed a hey-look-at-me spark plug in the exhaust, though flames shooting from the tail pipe would be kind of cool.
I also have a ticking sound when the car is warmed up, but I don't think it's a valve since it doesn't sound like it's RPM-dependent. However, if it is a valve, it could potentially be related to the backfire.
When I rebuilt the engine about 4000 miles ago, I had the head serviced. Redecked, valve guides and springs. I had a sticking valve initially but it worked itself out over the first 50ish miles.
I've looked for exhaust leaks and haven't found any.