720 with idle problem

[89720]

When I first start my truck it idles normal then as soon as I even tap the gas it jumps to 1500 and stays there for about 3-4 minutes (feels like forever though) and then sometimes it goes down somtimes it wont. been looking around on here and maybe a vacume leak or mabey my butterfly is gummed up not to sure any suggestions would be great...

[nissannut1992]

mine does that too, and I can't figure out why. I always thought that was because it was cold.

[89720]

well it has been cold since i have had it i notice i have like 2-3 vac lines not there. also i noticed today i have a throttle body not carb

[bob_reynolds]

I had my oil and filters changed over the weekend and today I noticed that it was idleing at 1500 rpm which is not normal. When it's cold it idles at 1000 but after it warms up now its idleing at 1500. I checked all of the vacuum lines etc.

[89720]

I noticed on line missing and then one going from valve cover to the air filter housing has a kink

[brianzero]

Mine does this too, but I have NO vacuum lines except for the vacuum advance. I have no EGR either.

Specifically, Im idling at 900/1000 when cold, but when its hot it jumps up to 1500/1800. Im almost suspecting that the cause is the fuel pump...

[bob_reynolds]

After re-examination I noticed one of the vacuum lines was not seated all the way in the plastic clip that is designed to hold the vacuum lines. It was getting pinched so I pushed it all the way into the clip and now it seems to be ok...

[89720]

i not really sure about it especialy since the throttle body is after market oh well i guess i will deal with it

[flinterman2000]

When the engine is cold there is a lot more restriction to movement causing friction which causes wear. As the engine heats up it expands allowing freer movement of parts. The less the restriction the easier to move. The carb or fuel setting is what brings up the rpm as the engine turns over easier. Setting the carb when hot should help. For the fuel injected engine the opposite is supposed to happen. When cold the ECU sends a signal to the injectors to allow more fuel in the cylinder. As operating temp approached the ECU cuts back the amount of fuel and the engine goes back to normal idle. Your ECU will need to be checked as the operation is backward.