Re: ? for Merc 575SCi experts
 

BillR,

Mine do the same thing. I talked to a number of techs and Mercury and they all said that they pretty much all do that. It seems to take a while for them to come down to an idle.

Re: ? for Merc 575SCi experts
 

Well you can tamper with the stop all you want but it will not help your idle come down if the IAC thinks it shouldn't. All the stop is for is to keep the blades from jamming in the throttle bore under the return spring pressure. If you bench test the IAC with 12 to 13 volts it should operate properly. However I have noted erratic behavior & numbers from GM IAC’s and TPS’s respectively when the voltage is higher than 14. Sometimes your alternators will bump the voltage this high. This can be the cause but most likely it is just a little sticky. Try an engine stop & restart and see if it doesn't idle properly.

Roby

Re: ? for Merc 575SCi experts
 

There is a parameter area to change this in the computer. Since I've had a laptop while running on the water on mine and completely reprogrammed my ECU after the intercooler/pulley change, install I have adjusted this flare. The problem when adjusted too low was that the engine would not get enough fuel shot to start properly when cold. Also, without the merc password you have to erase your ECU and program from scratch to remap the fuel and all these parameters.

Re: ? for Merc 575SCi experts
 

Can't you save the Merc settings and totally remap w/o password??
on your laptop that is?

Roby

Re: ? for Merc 575SCi experts
 

It is view only without the password. You can see all the Merc parameters but you can't upload permanent changes to the the ECU parameters without the password. Consequently, we erased and started with a base program we got from Dustin. I suppose you could try to write all the data to paper and then re-enter the data to a new file as a start. Not sure that I wouldn't do it that way next time.

Re: ? for Merc 575SCi experts
 

The throttle stop does a little more than keeping the throttle blades from hitting the bore. Merc adjusts the relationship on the dyno so the computer will be able to idle the engine at the desired speed with a combination of air bypassing the IAC and air going bye the throttle blades. The optimum combination is to give the IAC the ability to have air bleed range on either side of the desired idle speed as commanded by the ecu. The trouble is that the engines vacuum signal is not constant through the life of the engine and as it fades this factory set relationship may no longer be optimum.