Engine Won't Idle below 1100 rpm

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pcuccatti

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My throttle linkage is set corretly and the engine will not idle below 1100 rpm. I have a 1996 mercury mariner 250 hp EFI 3.0 Liter. Assuming the linkage and idle stop screw are set correctly, is there anything else that controls how low the engine will idle. I assume the timing is controlled by the ECM.
 
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pcuccatti

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Re: Engine Won't Idle below 1100 rpm

Thanks, however, I have the manual, did the link and sync and still can't get the engine to idle below 1100. The TPS is set correctly, throttle linkage is set correctly with the idle stop screw correct as well, the cam roller is seated and aligned properly. The engine does seem to spit out from the exhaust.
 
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CharlieB

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Re: Engine Won't Idle below 1100 rpm

Momentarily push the choke/enrichener while running to ensure that the engine speed changes, indicating that the enrichener is not stuck on.

Check for a possible intake leak by spraying along gasket/mating edges with a quality flammable solvent like carb cleaner or pre-mixed fuel in a spray bottle.

Remove and test both temp sensors with an ohms meter and heating them in a pan of water on the stove, a faulty temp sensor can trigger the ECU to enrichen the fuel map 10% and cause a higher idle.
 
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pcuccatti

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Re: Engine Won't Idle below 1100 rpm

Charlie,

I have removed the intake temperature sensor, put the ohms meter on 20K and cold it read 9.5. When I placed it in hot water, it dropped to 1.3. Does this mean it is good. What max/min ohm value range am I looking for? And thanks for your help.
 
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CharlieB

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Re: Engine Won't Idle below 1100 rpm

Without the 'Book' I cannot tell good/bad.

The temp sensors that I meant are the engine head temp sensors, here again you will need to know the values in the Factory Service Manual.

Hopefully anyone with access to the Manual will you please post values?
 
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