I start the engine cold and it putters and starts to misfire. At this point it either revs itself to 1200 for 5 to 10 seconds and then drops back to 600 with a few more misfires or it stalls. If it stalls then I restart it, it misfires a couple times, then evens out.
Sometimes I put it into drive at this point and the acceleration is a little choppy for a few seconds. There is a stop light 1/3 of a mile from where I start. By the time I get to that light and stop, the car is idling normally and has no acceleration problems.
These rough starts only happen on a cold engine that has been sitting.
Times:
Restart on a warm engine: no issues.
Sitting for 2 hours: no issues.
4-6 hours: no issues.
8 hours: May or may not start rough. If it does, it’s minor.
12 to 16 hours: This is where the misfire show starts. I haven’t let it sit longer that about 20 hours.
I’m wondering if you may have low compression when cold, due to the valves
This would be a valve lash issue, though. With the engine cold, the valve lash is insufficient, and you have low compression. Which leads to hard starting and a rough idle for a time. Then things warm up, the valves seat better, compression goes up. At which point, you can shut it off, and restart a few minutes later with no problem
I’m going to guess this engine has hydraulic lifters, but that doesn’t mean they’re functioning correctly
“My assumption is that I have a leaking injector…”
I would think a leaking injector would cause hot start problems (not cold). Since the issue is with cold running, maybe you need new engine/coolant temperature sensor(s).
Re: Does fuel pump turn on w/key in “on” and engine not started?
Not on my early 90’s Corolla. I think it may be possible for the fuel pump to turn on with the key in “on” with the engine not started, b/c I believe it did that a couple times when I was testing something where I had to prior depressurize the fuel rail. But the fuel pump has never turned on unless the engine is cranking/running in normal day to day driving situation.
Whether it does on your car, I don’t know, as this function varies from car design to car design.
The computer should ground the fuel pump relay to cycle it on for 2seconds when the key is turned on and then cycle off until the key is turned to the crank position when it is turned on again. Once the engine is running oil pressure closes a switch to power the fuel pump.