2007 Z300 Hard starting and Idle when cold

[basscat348]

I have a Z300 2007 that is hard to start when cold or first thing in the morning and even when idiling for trolling you can tell its running rough.I have check fuel pressure with key on and its good and checked fuel pressure while running and its good.I have adjusted the tps for proper voltage and have performed a sink and link and the problem is still there.I have 1200 hours on this engine and have run ring free the whole time but I am almost 99% sure that its the fuel injectors and they need to be cleaned or possibly the o2 sensor.I would hate to pull the injectors if I dont need to but I have seen them need cleaning at 300hrs before with no carbon additive in the fuel.If you have any other thoughts please let me know.I was a certified yamaha tec for a few years so this has me kind of scratching my head here.

 

[rodbolt]

Re: 2007 Z300 Hard starting and Idle when cold

need to recert.
the Z300 is a 3.3L block and none of the Z 3.3L blocks EVER used an O2 sensor in the US market.
how is the high pressure rail pressures?
are the temp and air pressure sensors functioning correctly?
ring free wont affect the injectors but dirty fuel can.
remember that engine has 3 fuel systems,low pressure lift,medium pressure,VST and high pressure about 1100 PSI.

 

[basscat348]

Re: 2007 Z300 Hard starting and Idle when cold

Everything is functioning correctly according to when I hook it up to the computer . I have not replaced the low pressure lift pumps yet.After the boat gets above about 2500rpms everything smooths out and runs perfect but before that the engine is really running rough,almost seems like one cylinder isint getting any fuel but then as soon as it passes about 2500rpms perfect.