I was replacing the spark plugs on my 2001 2.3 with 120k on the engine and noticed that there was some oil in the spark plug threads and the plugs on cylinder #2. I also saw that the CHT (cylinder head temp sensor) was installed but disconnected at the wiring harness.

I recently bought this truck and I've had some hesitation coming off idle, hence why I was replacing spark plugs and wires. I don't have a check engine light or any codes stored (I checked with my scanner, and my CEL does work), which was surprising since I've been driving around without the CHT connected. Can anyone confirm that should cause a check engine light? What would symptoms be for driving without it? And is it safe to assume the oil is from a leaking valve cover gasket?

 

Yes, oil is coming from valve cover

Yes, disconnected CHT should set a code
Possible codes seen here, there are others
P1288 Cylinder Head Temperature Sensor out of Self-Test Range
P1289 Cylinder Head Temperature Sensor Signal Greater Than Self-Test Range
P1290 Cylinder Head Temperature Sensor Signal Less Than Self-Test Range
P1299 Cylinder Head Temperature Sensor Detected Engine Overheating Condition

Just FYI, CHTs run hot, 240-250degF is not unusual, because its not coolant temp its head metal temp

Diagnostic codes have a generic code list shared by all vehicle makers, those are the P0xxx codes, i.e. P0301 means #1 cylinder misfire for any vehicles, not Ford specific

P1xxx codes mean different things, they are car maker specific, so P1288 is a Ford specific code, same code might mean something different in a GM or Audi vehicle

 

Awesome, thanks! I will try running it with the CHT plugged back in and see what happens.

Does anyone know of detailed instructions to replace the valve cover gaskets? I have only found vague youtube videos and instructions online. I'd appreciate it if anyone could send me the pages of a detailed service manual.

What other parts should I replace while I'm in there? Intake manifold gaskets, PCV, heater hose, etc.? And how can I source new valve cover bolts? I haven't found them anywhere online

Any answers would be appreciated!