My Galant is having the above problem. I am providing some details (below) related to the problem:
a) Check engine light was on. I took to a repair shop. The code was non specific. They did engine tune-up. The problem was not fixed.
b) I took to Mitsubishi. They could not find any specific problem. They recommended changing CAM sensor. After replacement, problem still remains.
c) Recently the car does’nt want to start. Check engine light is gone. Reving is still there at start and during stops.
d) I have noticed some of the coolant splashing out to the adjacent tubing during driving. The coolant chamber is empty. But the engine heating indicator is in the middle.
If there’s a leak in the cooling system where the coolant level gets low and air gets into the cooling system, and if that air gets to coolant temp sensor for the computer, the computer can think the engine is cold. So the computer raises the RPM’s.
Coolant temp sensors are meant to read liquid temperature. Not air temperature.
-The code was most likely for “Temp circuit out of range”
-Any good mechanic would know that a faulty cam sensor wouldn’t be first suspect in a case like that, if having any relation at all.
-By now from running with no coolant i would suspect head gasket loss of compression.
-As Tester said - they are meant to read a liquid temperature, air doesn’t have enough heat transfer to work that way.
Find a better shop and have them find/repair the leak AFTER they test the headgasket.
Leak in the cooling system can be difficult to trace, especially if it is internal. Minor leaks can sometimes cured by sealing preparations, but leakage from radiator cannot be done by your own, and it is better to consult any auto repair service. The last time when I suspect an internal coolant leak, I checked with Apex Automotive in Edmonton. If the cooling system springs a little escape, you need to look for temperature gauge and if it gets into the danger you require to quit and allow the engine to cool.
Not that difficult per-say, you can check the plugs and usually if one is cleaner than the other it will be there that it is leaking (assuming it got past the fire ring), pull your dipstick and see if it looks like mayonnaise or baby poo - sure signs of a internal leak.
it sounds like he is already aware where it is leaking from.
another note from above is that “leak fix miracles” don’t generally work - you could try an aluminum based powder one and pray but that is about it.
My money is still on the head gasket losing compression and now leaking.