Car revs high after start up

[webb1624]

Looking for a little help with my car. This issue only happens when the car is up to temp, 180 +. Cold starts are fine. When I start the engine the rpms go to over 2000 and immediately settle down to where they are supposed to be (950 rpms). The PWM idle cranking duty for the IAC valve when at temp is 45, and the PWM idle duty for the IAC valve at temp is 54. So I have it set lower at cranking but the engine still revs after start up. My crank to run taper is set at 0. Is there another setting in TS that I am missing ??? I have attached MSQ and a log of what I'm currently running.

[nathanhardy]

two things to check first do you have the diode installed? second some valves actually open below a certain duty cycle IE 30% is closed lower opens higher opens... run test mode and pull the valve off and see what setting actually close the valve... without that diode in there it can do some weird thing mine liked to idle up out of no where

[webb1624]

I bought the MS3X already assembled. Not sure if the diode was installed. Ill run some test to see if it changes if I close it or open it more.

[nathanhardy]

I believe the diode is something you need to install yourself since they don't know what setup you'll be running and it's not need on anything but pwm .. The info is in the hardware Manuel super easy to install it's installed at the valve not MS as far as the test mode stuff I tested mine unbolted so I could see the internal action.

Ps it's in the Manuel under pwm idle control

[nathanhardy]

http://www.msextra.com/doc/pdf/html/MS3 ... e-1.4.html

[webb1624]

What does the diode actually do ?

[nathanhardy]

best i could figure is it lets the 12volt spikes from the coil in the valve cause by turning it on and off flow back to the battery instead of going into the 5 volt or MS grounding system causing sync loss and other really weird things.. aka my car would be warm and nothing it ts would be causing it to change idle but all of a sudden mt rpm would shoot up to 1500.. took me a long time to figure it out and in you case its worth a try.

[webb1624]

Ill look in to that and give it a try. Do you have a 2 wire or 3 wire IAC ? Mine is a 3 wire
Thanks for the information

[nathanhardy]

Mine is a two wire. I'm not sure about three wire setups.

[webb1624]

My mistake. I actually have a 2 wire IAC. Not sure why I was thinking I had a 3 wire. I will install the diode and see if that helps my issue.

[webb1624]

Installed the diode today and it made no difference. Car still revs after it starts when up to temp. I thought it might be lean at start up so I added fuel to the ASE, adjusted the ASE taper, still no difference. This is the only issue I'm having with the Megasquirt. Everything else works great. Is this something I'm going to have to live with?

[slow_hemi6]

Something strange is happening. what happens if you make the last point of cranking duty 200f 44% and the last point of Idle duty 200f 52% ? Just so it is actually operating within the defined curve and not past it. What would the log show duty% for crank and idle at 190f ish with that change?

[webb1624]

That's interesting. I've never thought of doing that. I might have some time tomorrow to mess with it. I'll give it a try and get a log and see what happens. I also want to get a log of the cold starts where it doesn't rev to see if anyone notice's something that might help diagnosis the issue.