noise when starting the car

[logicmobile]

hello everyone im new in this forum my name is homer and i have a 2003 infiniti g35 and i have little problem , when i start my car from long time sitting lke 5-8 hours as soon as its about to start it makes a bad sound like pounding hard ( just one time ) but if you turn it off and start it again no more smooth start,,,,if anyone got same problem and you figured it out pls help....

[G_whizz]

Welcome to NICO!

I have posted this question in the Mechanic Forum...it should be answered shortly.

Now...post some pics!

[qship96]

starter grinding?

[joe603]

sorry gotta do it......DOH!!!!!

[elwesso]

Hmmm... Ok, so when you go to start the car it makes a GRINDING noise or a POUNDING (like thump thump) noise...? Sounds like what your saying is right before it starts it makes a single thud and then goes smoothly? Or what?

Please elaborate. Has this problem always been there? If not, when did it start? Any history is needed to diagnose.

[mks8882]

My '03 does the same thing. When you first start it after it's sat for a while the motor turns over and right when it starts you hear one single "Bump". It's not the starter and it's not a grinding. And like he said it only does it when the car has sat for a little while.

[ScottJackson]

If it's a single thump just when you start to crank the motor, I'd say to look for a leaky fuel injector (or injector 0-ring). If it's a clatter that begins right when the motor fires up and then goes away in a second or so, it's probably chain tensioners leaking down and the timing chain clatters until they pump up with oil pressure (could also be hydraulic lash adjusters leaking down), but I don't know if the G35 has timing belt or chain or hyd lash adjusters. If it makes a popping noise only while cranking the starter, it's a cracked flexplate.

[logicmobile]

before i explain it , i just wanna say thank you for a warm welcome for me in this place where eveyone help each other....thank you guyz

ok it not grinding , its pounding like ( thag!) thats what i hear , im thinking its something got to do with gas stuff , so i figured like gas build up and then when fired up make that big noise,,hope not

and for picture ill try to post one but its just stock form right now nothing change but i will.......

[logicmobile]

this problem only happens every time the car is got siiting in a couple hours, i havent tell anything to the dealership yet , but i will soon...

[texasoil]

could it be the first cylinder firing real hard and shifting the engine on its mounts?

I had an airplane once (1963 Mooney Mk20) with a 180 Hp Lycoming 360ci engine and instead of an impulse spring on the magnetos it used a 'vibrator' to generate the starting spark. It would fire with a 'thump' every cold start--that was normal.

[logicmobile]

well hhhmmmp ....thats little relief but hopefully wont hurt it , thanx for your help