real low idle

[Cincinnati Guy]

I noticed the past few days that sometimes my truck idles real low, my RPM shows about 400 RPM at idle. It is usually about 500-700 RM at idle. I also noticed my high idle didnt kick on. What could be wrong? Seems to run fine but just the idle problem.

 

[Cincinnati Guy]

Now I go out and start it and its idling fine. Could it be my fuel filter?

 

[OLDBULL8]

Do you press the go pedal down to set the Hi idle when starting? How about a loose connection on the cold advance solenoid ? Bad contacts on the motor temp sensor under the t'stat housing ? That powers the Hi idle solenoid until motor temp reaches 112* . Hi idle should be around 900 - 1000 RPM, Lo idle at 650.

 

[Exekiel69]

This may not be the problem, but a clogged fuel return line can lower rpms till it stops the engine.