I have a pure-stock 1993 RX-7. When I first get on the gas, after warmup, the engine hesitates for a second or two (essentially no power) then takes off and runs normally. What are the most likely causes?

 

Just means it isn't actually warmed up yet so the double throttle (keeps 2ndary ports closed) is staying shut so you don't rail on it when its cold.

If you really think it is warmed up when it is happening check that the coolant temp sensor that reports to the ECU is working in its proper range. It is the upper temp sensor with green connector on the back of the thermostat housing (front of engine).

 

Thanks for the info BLUE TII. You may be correct, I'll drive at low rpm with mild acceleration until engine is hot then make a hard acceleration test. If it still hesitates, I'll check the coolant temp sensor as you suggest. Wow. This is a great site for information. Thanks again.

 

I still get the hesitation for 1 or 2 seconds on first hard acceleration after carefully warming up the engine to normal operating temp. The coolant temp sensor seems to be operating properly both at cold and hot. The spark plugs were due so I replaced them but that didn't solve the problem. (The plugs were worn but not fouled.) Can anyone think of other potential causes of the hesitation?