I've recently been having troubles with starting up my 04' G35 Coupe (especially after sitting for more than 8 hours). The problem started occuring a couple of months ago where the starter sounded a little funky. This only ever happens on a cold start. If I were to start the car, turn the engine off, then turn it back on, the problem goes away.

I've changed my battery and starter (7k miles ago), as well as the spark plugs (4k miles ago). I also recently had a CEL for my Variable Valve Timing Solenoids, which I also replaced 2k miles ago. Over time, the cold start began to get more rough and rough, however, the car is still cranking and turning over. No CEL or any lights on the dash. I brought the car to AutoZone to scan for any codes, but none showed up. There was one morning where I started the car and went to get gas and as I was filling up, the gas nozzle kept releasing as if the tank was full (even though the tank was empty). I consulted one of the workers at the gas station and they told me it's due to fuel pressure. My guess would probably be the fuel pump.

So I was curious and decided to look up on different forums and majority of people said to get the Techron Fuel Cleaner. I tried it out and the problem is still happening. Even though the problem goes away after the cold start, I'm just worried it might cause problems down the line and potentially not start one day. Any suggestions to what may be the cause and if there are any solutions?

I've also uploaded a video below of the cold start to help visualize the problem. Thank you!

 

The trouble refilling the fuel tank is a separate issue, the fuel station tech doesn't know what he's talking about.

Basically how it works, you pour in fuel, the trapped air inside the fuel tank needs to be displaced but the breather tube has blockage so the displaced air has to come back up the fill tube which shuts the gas pump off.

Your cold/hard start sounds like a parasitic draw on the battery or a bad battery, low cranking amps, and the problem seemingly "disappears" after a second start because the alternator has charged the battery up a little more. I bet if you just didn't start your car for a week the battery would be dead.

EDIT: Are you still throwing a CEL?

 

Thanks for the reply. I took your advice on the battery and exchanged it for a new one. I also noticed a bit of corrosion on my terminals and replaced those for new ones as well. No issue for a few days but noticed the starter to sound a little funky again. Car is still cranking pretty well but there's a slight pause before the engine is turning over, but it definitely wasn't as a bad as before I exchanged the battery. I can try to capture a video within the next few days to help visualize. Still no CEL or anything. I tested the battery voltage which was ~12.7 V and the CCA which dropped to ~11.1 V then rebounded to ~14.6 V. I attached a video of the multimeter results. Do you have any other ideas what might be the cause or any solutions that can help? Could it be a problem with the electrical system/alternator/or fuel system? Thanks again for the help!

 

The rough (cold) start is still persistent even after I changed my battery and terminals. No CEL or anything so far. Any other recommendations?

 

Sounds like the starter and flywheel gears are not meshing properly. You may want to remove the starter and look at the gear for damage or excessive wear.