5.7 surging/low idle

[croaker567]

Hey guys I've got a few problems with my truck that I've had for a little while. Ok quick introduction I bought the truck with a blown engine in it. Bought a new short block and had the heads worked and everything put it all back in and together ram and everything but now when idling it has a surge. The rpm barely drops up and down but you can definitely hear it and notice. Also when I crank it up at first it'll idle around 900 rpm then when you drive it and come to your first stop sign or red light it'll drop to around 550 and 600 and that's when you really notice the surge. I'm most likely going to clean the throttle body and its throwing the code p0456 and p0441 could that have anything to do with it? Also I have a slight whistle when taking off think it may be a vacuum leak that I'll check. Sounds like a turbo. Any help out advice or anything would help out greatly.

 

[croaker567]

Both closes have to do with the purge system. Also p0593 which is cruise control and p2173 and p2106 last two just popped up

 

[croaker567]

Also sometimes when I shut it down there is a loud air blowing noise. Kind of like blowing air out of an air compressor

 

[PCA4208]

Idle is normally about 500ish on an 03 truck. no getting around that without doing a special mod to the engine.

Clean the throttle body, also the pcv valve. The p0441 I get a lot, and usually it fixes itself when i remove the gas cap and let the gas vapors escape.

 

[croaker567]

Alright well its good to know that my idle is right but. I definitely have a vacuum leak

 

[Redtruck-VA]

Alright well its good to know that my idle is right but. I definitely have a vacuum leak

There are two vacuum hoses, one going to the brake booster and a smaller one just behind the booster hose on the manifold. Hard to see but you can reach around and feel it. There is also a rubber cap on a test point on the booster end of the hose that sometimes gets knocked off. A 03 should idle 525-550 rpm warm and 750-800 cold. I'll sometimes use a plain 1/2" hose about 3 feet long and use it like a stethoscope listening back in spots hard to reach for various noises.

 

[croaker567]

Ok I'll try that and see what I get. Thanks guys

 

[croaker567]

I'm missing a hose to my tb. I have the one hooked up my brake booster but theres one sucking air right behind it. Where does this go?

 

[smarsmar101]

Can u just take it to the dealer? Or did I miss that part?

 

[croaker567]

I don't take stuff to the dealer lol might be part of the problem

 

[Redtruck-VA]

That's the one that's easy to miss. It goes to the purge valve located in the lower forward driver side of the engine compartment. It has the hose coming from the manifold and the other hose goes to the NVLP located in front of the emission canister in front of the gas tank. The one you have missing is a hard plastic tube with about 4 inches of rubber hose stuck on it's end that fits to the manifold.

 

[croaker567]

When I plugged that in it started running like crap and really rich so I'm going to reset the computer because it ran for a long time without that tube on so it may have adjusted a few things

 

[croaker567]

Runs better now but still not perfect so I'm gonna drive it tonight and see what happens