F115 idles at 900-1k rpm

[Extreme26]

Hi,my 2006 f115aet is idling at 900-1k rpm currently.....it used to idle at 700-800rpm...i have hook up yds but unable to analyse what is out of specs...hope someone can point what i should look at.

[Extreme26]

[fairdeal]

Hopefully Rodbolt explains this to us..






if the ECU is unhappy with a sensor it raises the idle to '900' rpms
but that doesn't seem to fit with what I see here
besides everything reported as 'normal'...


I don't understand the ISC request at 50% - but then I don't know what is 'normal'
if the ECU wanted the rpms at 1048, wouldn't it be higher than 50% ?

and if you had, say, a manifold leak or throttle plate problem,
wouldn't the request be as low as possible to get the idle back down?

and the timing at 4 ATDC seems like it should be a clue...

[Extreme26]

Thanks for the reply fairdeal.I just got the yds,first time hook it up to the engine to monitor the idling issue.Missed the steps to perform static test on the isc and other sensors...i do notice past diagnosis records.Does clearing them up reset the ecu?

[Extreme26]

Engine has no other issue than this idling problem...wot at 5900rpm,no surging...running smooth all range...only sounds clunky when push into forward & reverse due to higher rpm.

[Extreme26]

Hi fairdeal...what do u see regarding the ignition timing?

[99yam40]

do you have a service manual for that motor?
I would think it would have the timing spec for timing

[Extreme26]

Hi 99yam40,thanks for the reply....i do have the service manual,it indicates ignition timing at 4 ATDC...am i correct?

[99yam40]

yes that is the idle timing, so it looks normal.
there is some other thing going on.
I am not sure if the ISC should be at 50% or not.
Rodbolt needs to have a look at this thread

[dray0151]

Your service manual should give you normal values for things like the ISC. Rod has and the others on here have a process for lynch and sink if that ISC value is to high. If I remember correctly my 2004 f115 was around that value. Also you might check the intake pressure thermosenor. If it is out of spec you will idle wrong and even if it has just vibrated loose it will effect your idle. Mine had vibrated loose increased the idle up. Thought it was bad but checked, tightened it and all was fine.

[pstephens46]

Your service manual should give you normal values for things like the ISC. Rod has and the others on here have a process for lynch and sink if that ISC value is to high. If I remember correctly my 2004 f115 was around that value. Also you might check the intake pressure thermosenor. If it is out of spec you will idle wrong and even if it has just vibrated loose it will effect your idle. Mine had vibrated loose increased the idle up. Thought it was bad but checked, tightened it and all was fine.

How is the Merc? Which model do you have? Can’t remember.

[rodbolt17]

and what is the ISC in %, it is a REQUEST.
the ECU has no clue if it actually moved.
the ISC controls the idle speed .
try using the dynamic function of the ISC on YDIS and see what it does.

[dray0151]

How is the Merc? Which model do you have? Can’t remember.

Merc is doing great just not getting out enough here in Missouri! Can't wait for March to get here!Tthe merc is a 2012 150 four stroke. A real nice machine.

[pstephens46]

Merc is doing great just not getting out enough here in Missouri! Can't wait for March to get here!Tthe merc is a 2012 150 four stroke. A real nice machine.

The 3 liter I assume. The track record appears to be very good. Times are a changing for Mercury it would seem. That is a good thing. Optis and Verados got a lot of bad press the last 15 years or so.

[dray0151]

Yep the 3.0liter! Thought I read somewhere you can't order a Verado in 150 anymore, I think its Pro XS, four stroke and seapros you can get 150's? Not sure on that though. Saving my pennies now to get the diagnostic software Rhinda has like i had for my Yammy. It's just a lot more expensive. I really only want it so I can tinker like I did with the f115 when I want to.