Problem with idle speed on f115 four stroke.

[cobb3333]

The problem im experiencing is when I switch off engine and restart ,it restarts reving at around 1500 revs and slows down to normal revs (700) after about 10 seconds , no big deal I know. I have to wait for the revs to drop before I put it in gear , which annoys me slightly. The iac has been replaced , also the throttle sensor, the throttle sensor has been adjusted to .731 v dc as specified. Anyone experienced the same problem , or can point me in the right direction to identify the problem. appreciated

[rodbolt17]

that's how they work, usually slows down faster if the ecu gets the correct cts signal.
that rattle you hear at shutdown is the isc valve reseting to 100% in anticipation of the next restart.

[cobb3333]

Thanks for the reply Rodbolt. Is that a signal from the tps you are talking about.I can live with it as it is , but if it can be improved I would like to do so. I can recheck the voltage to the tps , with another multimeter as my one is a fairly cheap version.thanks again for your help

[boscoe99]

Listen to an F250 outboard motor (or my F150 pickup truck) start and you may think the motor is running away with itself. They run at a very high RPM for a bit of time.

I always like to wait for a motor to be thoroughly warm and at a low idle before putting it in gear. The wife on the other hand goes directly from the key switch to the shift lever and puts it into gear a nano second after the motor starts. The RPM be damned. I just wince and keep my trap shut. If I know what is good for me.

[cobb3333]

Listen to an F250 outboard motor (or my F150 pickup truck) start and you may think the motor is running away with itself. They run at a very high RPM for a bit of time.

I always like to wait for a motor to be thoroughly warm and at a low idle before putting it in gear. The wife on the other hand goes directly from the key switch to the shift lever and puts it into gear a nano second after the motor starts. The RPM be damned. I just wince and keep my trap shut. If I know what is good for me.

Hi Boscoe, I would expect it to do so on a cold engine. My engine does it everytime even if it is hot. ( switched off and straight back on).
If that is normal , I will happily accept that. Save me trying to fix a problem that does not exist.
By the way you are certainly switched on regarding the fairer ***. (lol)

[rodbolt17]

its pretty much normal, hook a tach up to most any EFI engine and you will see the same.

its due to the ISC(IAC) resetting to 100% at key off.

at 100% you get a very high idle.

once started the ECU then starts looking at various inputs,mostly the CTS(coolent temp) and the TPS and the pulser coils so it can figure out what RPM is commanded by its internal mapping.

ya outta see the F250 and the F350 at engine start, if they start at all its instantly at about 2500 RPM.
its rather violent.
if your TPS voltage was off,guess what.

you would simply never see the 700 RPM idle.

if any sensor is out of range it idles about 1100.

the ISC is NOT monitored for any failures.

[cobb3333]

thanks for the information rodbolt, You have put my mind at rest .