Rough idle cold

[fallvitals]

My crew is starting to get a rough idle when engine is cold. Done it twice so far. Kinda maybe sounded like it was missing a little during? You could hear it kinda hesitate then when it hit it would 'jerk' the truck.

I was about to seafoam it, then this started. Maybe that would help, what should I look at? Spark plugs were replaced like 7k miles ago.

[HenryJ]

Clean the throttle body and the Idle Air Control valve (IAC)
I think you will find it pretty carboned up on the back side of the throttle blade.

[fallvitals]

I'll try that. That's separate from the throttle blade right? I cleaned it well when I did the blade mod last summer.

Just a funny FYI, I finally put my e fans back in. And I was running hot! Turns out I plugged em in backwards, lol.

[HenryJ]

That oblong hole the the throttle body throat is the passage for the IAC valve. Clean it out good with some throttle body cleaner. You might even remove the valve by unscrewing the solenoid body. You can then clean the pintle and seat really well. This controlled vacuum leak is what controls the idle speed. If it gets sticky or does not work properly, you get erratic idle problems.

The lack of idle speed indicates a restriction. That hole in the throttle blade is a metered hole for the correct idle speed. If it gets carboned up the IAC valve tries to make up the difference by opening slightly. It really is tough for it to meter such small amounts. It is designed to open when needed and close to catch up much like the accelerator pumps would do in the old carbed rigs.

If things don't improve when you clean it up, you might try replacing the IAC. I have had a couple get sticky and cause problems.

Another thing to keep in the back of your mind is intake gaskets. I have found at least one engine with bad gaskets that ran like crud until it warmed up a little. It was fine once warm. I guess things swelled enough to clear things up. I found a leak when spraying cleaner around the gaskets on the intake. The leaks were pretty small, but really raised heck with it cold. Once replaced it has had no further issues.
Rule out all the easy stuff first.

[killian96ss]

If you do take the IAC valve out to clean, make sure you don't move the pintle in or out because you can damage the internals pretty easily.

Steve

[fallvitals]

I think hitting it with the throttle body cleaner did the trick. Well it didn't idle rough before I left to get the cleaner this time. But my truck I though has been idling way high for a while, 1000 rpm once warmed, it would drop to around 800 rpm (all in park), when in a drive gear it would fall 1-2 hundreds rpm. Hit that oblong hole in the back of the body with the cleaner, at first I didn't think it was dirty, but it sure was.... Had a hard time getting it started once done but idle was way down, around 500-600 rpm in park.

Time will tell, but seems like it was likely the issue. Maybe it's me, but the truck also sounded better, louder, "throatier", once I cleaned it. Guess I'll get it warmed up again and try to seafoam it.