2007 Mercury Milan, 2.3 automatic. Engine has a dead miss with no check engine light. Also cooling fans run at high speed continuously. I have smoke tested engine, new plugs, coils, injectors, mass airflow sensor, and coolant temperature sensor. Everything tests good and compression good and leak down are within specs. Any ideas?
Because the fans are running constantly it sounds like you have a communication problem between modules, sensors and the ECM. You need a good local auto electrician with a pro grade scan tool computer. This is not an easy fix that you can do at home because the scan tool is about 5 grand.
Replace coolant temperature sensor
Testimonial: "Checked ohms on cts reads same as new taken at 3 different temperatures also I have approximately 5 volts harness reading"
It may be the harness
could be stuck closed contacts inside a relay for fan high control .
Could be a number of thing's , quit guessing ,have a qualified repair shop check it .
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Do you know how to check computer drivers ? computer drivers are transistors inside the PCM - engine computer , this drivers turn on fuel injectors , control the coils . Have seen ford vehicles with coil on plug ignition system ,spark plug gap was to wide causing the coil to over heat ,short out an short out the drivers inside the engine computer . If you have coil on plug ignition system the driver inside works just like this in the video.
https://www.youtube.com/watch?v=JTCgUY51...
You replaced all those parts - you may need another one - PCM - engine computer , and it will need to be programmed -
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Did you hook up a scan tool an check codes ?
P0480
P0481
P0482 Fan Control (FC) Circuit 1, 2 or 3, respectively
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