High idle

[InspectahDEck]

I have been having an issue with my 05 yukon denali, where the idle is higher than normal. Upon starting the truck, the idle appears normal, but after a few minutes when I come to a stop, the idle is around 1k-1.5k.

It seemed to be worse when it was warmer outside in the past, but now it always does this after a minute or two of driving in any condition.

When coasting around 20mph the idle actually keeps the vehicle moving at the same speed, sometimes even increasing speed. At a stop light, just barely letting off the brake the vehicle really wants to start going, so I have to press the brake a bit harder than normal.

I was thinking maybe the MAF or throttle body, but a friend said o2 sensor? Any suggestions on where to start would be greatly appreciated. I recorded a video of it idling FWIW

 

[RET423]

Usually I would start by looking for a vacuum leak but with that high of an idle you should be getting a code.

 

[Fless]

Recommend cleaning the throttle body and whatever you can on the Idle Air Control (IAC).

 

[strutaeng]

Recommend cleaning the throttle body and whatever you can on the Idle Air Control (IAC).

Agreed. This vehicle should have DBW IIRC(?)

Do those DBW have IAC? Regardless, cleaning the throttle body should be the first step...

 

[rockola1971]

Need a scanner to see if Engine Coolant Temp sensor is reporting the correct temp (Not to be confused with coolant temp sensor that feeds your temp gauge signal). The ECT tells the PCM whether the engine is cold or hot starting. PCM might think you are running a cold engine and is the fuel injection version of "choke mode".

 

[Fless]

Need a scanner to see if Engine Coolant Temp sensor is reporting the correct temp (Not to be confused with coolant temp sensor that feeds your temp gauge signal). The ECT tells the PCM whether the engine is cold or hot starting. PCM might think you are running a cold engine and in the fuel injection version of "choke mode".

Why do I forget about this?

 

[rockola1971]

Why do I forget about this?

Because you could be getting old like me. <shrugs>

 

[InspectahDEck]

ECT sensor appears to be fine, reporting seemingly correct Temps during cold and hot start. Cleaned the TB yesterday, have not drove it yet but seemed the IAC is riveted to the TB directly? Unless I am looking at the wrong assembly