Mercury Repair Questions? Ask a Mechanic for Answers ASAP
Hello and thank you for your question,When the check engine light comes on the computer should always set a fault code and or codes. Who ever you had scan it may not have done it properly. If the light is on, can you stop by your local parts store such as Auto Zone and have it scanned again and see what the fault code and codes are. They will do this for you at no charge as well. Post back with the results and I will advise you from there.
If the light is coming on there really should be a fault code setting. The light coming on indicates there is a fault code and or codes. Can they scan it while the light is on?
What year is your Mercury and which engine do you have?
Is this noise your hearing a squealing type noise?
One very common cause for this type of noise can be caused by a failing Camshaft Synchronize located on the front of the engine and if its failing it can cause the service engine light to come on and off. You can check this with a stethoscope placed on the Camshaft Synchronizer while the noise is occurring. If it turns out to be the source of the noise then it will need to be replaced. Its very common for them to fail as well. I have enclosed the location as well as replacement steps in the link below. Copy and paste the link toy our browser to open and view the file. Check this and post back if you need more help and or have more questions and we can work from there.https://dl.dropboxusercontent.com/u/104923897/Camshaft%20Synchronizer%20Feb%2015.pdf
Your very welcome and thank you as well. Please take a moment to rate my service so I can get credit for my time, the question remains open for follow up even after doing so, all you need to do is return to this question if need be.Thank you again.