Reasons a car could have a weak start up?

I have a 2015 Honda Accord and I've been having problems starting my car. I took my car to the Honda dealership back in August when I first noticed the problem. It would have a weak start or it wouldn't start at all. My battery and alternator test came back good and i just had a recall on my battery connects put on yesterday and I'm still having the same problems. What other possibilities are there to be causing this to happen?

It's just like basketball. You don't go out there and try to pull a Kyrie Irving dribble right out of the gate. You gotta warm up. Same concept applies to cars.

Cold air?

Most likely it is an electrical problem. These are hard to diagnose for the average mechanic. Take your care to a place that specializes in such problems.

The fuel pump is supposed to hold pressure when the car is off. Yours may be bleeding back over time. Common for modern fuel pumps.

Do an OBD2 code check for trouble codes and they will tell- not guess- malfunctions. Perhaps a new set of spark plugs can improve performance if the old ones are conventional. Then get platinum plugs. When you say weak, do you mean cranks slower than normal or takes a lot of cranking before it starts? The weather is changing to colder and if gas stations haven't gone to winter gasoline that might be a temporary starting problem.

Your terminology is not descriptive for a mechanic. A "weak" start-up means what?

Your car either starts or it doesn't. If it doesn't, then a trained automotive repair professional can find out why. If your dealership can't help you, then find a different repair facility.

Starting (the turning of the engine crankshaft by the starter) involves the following:
Battery
Battery cables
Starter/solenoid

If you had a condition where the starter was not operating, then you add: the control wiring, the ignition switch, the neutral safety switch and possibly the car security system to the list of possible causes.

Without having any idea from your weak description, I'd say to have the starter checked.

The battery voltage and starting current can be measured, and may point at something.

-General automotive mechanic since 1972

Cold start - engine oil too thick crankshaft rotation slower on cold start / engine.

Replace the battery. Get the fuel pressure checked. Fuel pump could be defective.

Old

Spark plugs