95 Merc 175 EFI inter. running problem, HELP!

I have a 95 Merc 175 EFI XRI that started to loose RPMs while trying to get on plane. Eventually it wouldn't plane at all. After working on it for a while I found that 1 coil was shorted out. So I replaced all 6 coils and the firing trigger. The engine seemed to run fine after that but now recently its been running real rich in the morning and when I first try to excelerate it doesn't want to plane out. Once I finally get it on plane it seems to run fine the rest of the day. It only seems to do this right at start up and after its sat for a while. Sometimes its worse than other times. I took it to be diagnosed on a computer but the shop couldn't tell me anything about why this was happening. They spent two hours looking for problems but couldn't find anything. The oil injection has been bypassed so that I can mix my own oil to be safe so I know its not incorrect fuel/oil ratio (50 to 1). These are the steps I've taken up until now:

Replaced coils
Replaced firing trigger
Replaced water fuel separater
Removed and cleaned internal fuel filter
Removed and checked vapor separater
Replaced all spark plugs
Checked high and low side of stator (stator is ok)

Has anyone had this same problem? If so please let me know what you did to fix it. I've been trying to get to the bottom of this for 4 months now. Thank you!

Re: 95 Merc 175 EFI inter. running problem, HELP!

There are two things that will not show a trouble code and need to be tested

poor fuel pump, it will make pressure at an idle and at revs (no load) in the shop but if you test line pressure IN gear IN the water the fuel pressure falls off

Injector spray pattern, if the injector is worn out it will spray much like a squirt gun instead of a nice fan/cone shaped mist, causing the motor to run rich and bog unless it is very well up to temp. As the injectors wear out even more it will get progressively richer until it totally dies/flooded. Pull the whole injector rail out but leave the fuel lines and wires attached, crank the motor and observe the spray pattern.

Re: 95 Merc 175 EFI inter. running problem, HELP!

From what you have done 2 things was not listed, the TPS and fuel rail pressure. If the tps is misadusted or bad it will act sometimes as you describe.. As for the injectors have never seen one wear out. Pull the injectors and send to Tony Brucatto and have cleaned and flow matched price is about 130.00 for all 6.

Re: 95 Merc 175 EFI inter. running problem, HELP!

Thanks CharlieB and Faztbullet. I did check the fuel pressure at idle in my yard and it was at 40lbs (+ - 2) I'll try what you have suggested and let you know how it goes.