I'm getting an intermittent cold start problem, and am not sure how to proceed.
Circumstances:
- "Cold" start (ambient ~75 - 85F / 27 C), after not driving for several days.
Symptoms:
- It starts first try, but runs very rough, bucking and missing, and fairly quickly stalls out.
- Simply
pushing the throttle causes it to bog and immediately stall out.
- However,
pumping the throttle constantly, I can keep it running, but:
(A) the tach is bouncing wildly (much more than actual engine RPM),
(B) it's backfiring occasionally through the intake, and
(C) it's missing and bucking and not generating any power, even at high RPM -- ie. almost impossible to engage the clutch and move the car without stalling out.
- The last 2 times this happened, after multiple attempted starts (like 20+), pumping the throttle, etc., the idle eventually smooths out and everything goes back to normal.
Codes:
- First time it happened, I nursed the car along to where I needed to go (about 1.5 km, mostly downhill), and got a code for a cyl #3 misfire.
Pulled the #3 plug wire, and the plug end connector FELL OFF. 
What I've tried so far:
Replaced all 3 wires, cap & rotor with good parts from the Firefly. No problems for several more cold start cycles after that.
- But it's happened 2 times since then with NO codes.
Any suggestions on how to diagnose this or what parts to systematically change to find the culprit? I have the Firefly to pull good parts from to ID the problem.
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EDIT - Comparison to no spark on one cyl:
So the cold start problem happened today. After 20+ starts/stalls/playing the throttle, the engine eventually went back to normal, and I used the car for a short trip. It worked perfectly.
Just for fun, I pulled a plug wire when I got back to see how the cold start problem compares to missing spark on one cylinder. It's not the same. The car is MUCH more driveable with one spark wire disconnected than it is when it's doing this bucking/missing/backfiring routine.