Engine revving by itself with high coolant temp

[sach]

Hello all. My isssue today is this, my 2006 Explorer engine is revving breifly and returning to normal by itself and the engine coolant temp gauge quickly rises to hot. Also sometimes when the gas pedal is pressed the engine revs with a loss /lack of power. When this happened I checked the Thermostat, it was functioning correctly. The engine coolant temp was high because the fluid was expanded in the expansion tank past the high level mark almost filling the whole tank. At first I thought it was air in the coolant system, but I can not tie in the revving issue (fan/pump related?). Possibly a sensor related issue? No trouble codes present.

 

[Flag Gibby]

The revving is normal for an engine that is running very lean because of too much heat and on the verge of vapor lock. Are you sure that the water pump is working/circulating the coolant properly. If you have no air in the system and you know for sure that the thermostat is opening up correctly and staying open then the only thing I can come up with is that you have a blockage in the cooling system or your water pump is failing.

 

[sach]

What do you mean by the engine running very lean because of too much heat and on the verge of vapor lock [Vapor bound Coolant system?]. Vapor/ Air bound was my initial guess based on temp gauge quickly rising to hot instead of slowly increasing. What is the correlation between the pump and engine rpm.Where does the lack of power with rpm increase come into play? Is there a way/procedure to test the pump for proper operation.

 

[Flag Gibby]

These engines are pretty intelligent in terms of being able to dial back the timing etc. based on sensor feedbacks so when it recognizes/detects the engine getting too hot it increases the fan speed to try to cool it down and when it detects a knock it dials back the timing until it is no longer detected. The water pump is mechanical and as the RPM's increase the flow rates increase; to my knowledge there is no easy way to check the pump in terms of flow rate (either all the fins on it are in place and are spinning or it is not).

On another note, when was the last time you changed the fuel filter? I doubt that a really lean engine could cause the engine temps to get that high, but I cannot rule it out completely. If it has been more than 30K miles then it needs to be changed, but the other way to see if it needs to be changed is to check the fuel line pressure at the fuel rail.

 

[sach]

Know of any place to download the powertrain control/ emissions diagnostic manual for the 2006 explorer. I have the Service manual, did not think I would use the PC/ED manual too much and did not want to pay the 150+ for it. Other forums (Infiniti, Honda...) have manuals to download, I have not seen any here yet but I am new to this forum. Any way members can upload their manuals for others to use? Thanks for your time and info.


Fuel filter has approx 3000 miles on it

 

[Flag Gibby]

I think that Ornery has that manual and he may be willing to send you an image of the sections that you need if you ask him, but typically the whole PDF is not available for our generation for free download yet. Most of the time you can find the critical stuff that you need by searching in this forum.