common vacuum leaks, The Elbow on the firewall side that plugs into the IAC and lead to the PCV. Others are the smaller vacuum lines that go to firewall side of the battery from there they go to the HAVC....that said check over all the lines. ( at least on mine) There is a vacuum canister in the passenger fender, behind the battery, that can leak too, but not very often. AND of course the intake manifold.

Is this unit 2wd or 4x4? If 4x4 then there is the vacuum lines going to the front axle.

Maybe your waiting until after the fuel filter change? Have you checked the fuel pressure?

 

Yeah I'll spend an hour or so and spray a bit of carb cleaner on all the lines. Hoping its not the manifold gaskets, but then again that would give me a good excuse to pull the throttle body and do a thorough cleaning on that.
It's a 4x4, so the tip about vacuum line on the axle is something I'll check. Definitely waiting till the plugs/O2 sensors/filter are in before ordering more parts.

Something else I forgot to mention that I found yesterday while i was under the truck; there's a rubber line that connects to the brake line splitter(?) just to the left of the rear diff on the axle housing. Its broken right off the nipple on the connector. It feeds up onto a connector in the frame and I cant see beyond that, but it IS broken off the connector, and the connector that sits in the frame is very loose.
This is a google image, but this is the exact line that's broken in the circle. Is that a vent of some sort?

 

The rubber hose is the vent for your diff.

 

Don't use carb cleaner, it's hard on rubber parts. Use an unlit propane torch.

It doesn't plug into the IAC, it plugs into the backside of the intake.

 

Yeah i know that way is better, just gotta go get one. I'll probably rent a fuel pressure tester at the same time to get a baseline of what my FP is before i even change my filter.

 

Would you guys recommend cleaning the EGR valve along with the throttle body just for the sake of being thorough? And if so, would I WD40 the valve shaft like the IAC? I want this thing to run like a top.

 

When you remove the throttle body to clean it, clean out the EGR ports in the elbow. It probably wouldn't hurt to clean the EGR valve, but I wouldn't put anything on the shaft.

 

In that case should i remove the IAC again and clean the wd40 i put on the shaft? And I'm assuming the "elbow" you're refering to is the TB to manifold adapter piece, correct?

 

WD-40 is fine in the IAC, that won't cause problems.

Correct on the elbow.

 

Well i didnt find any obvious vacuum leaks. But then again the probpem is intermittent so if its a vacuum leak its not a constant one.
Pulled off the throttle body and dear god.


I cleaned it up about 95%. I forgot to take an after picture but there was some stuff i couldnt get off with my crappy old tooth brush.

Here's down the elbow. Equally as coated as the TB. So where exactly are these egr ports?

 

At 120K in 2016 vacuum leak causing rough idle tracked down to cracked plastic intake manifold. Replaced with Dornan. Problem gone.

 

You never looked at or interpreted the code descriptions properly.
Codes 135/156/158/1151 are open rear Ox sensor leads both banks in the harness or wiring.
Codes 1130/ 1132 and 172 are all related. Likely again a harness issue under the truck.
Leave the rest of the motor alone unless there is a later need that shows up..
Good luck..