SOLVED: High Idle and Loud Hissing Noise

[Krmcfarlin]

I recently picked up a 2006 Ram 4.7 that sat for a few months so I’m getting it back on the road.

My only issue with the truck is that it idles high. In park it hovers around 1200-1500 depending on its mood. I’m not getting any check engine lights, while test driving it I’ll occasionally get an ABS and BRAKE light.

I’ve replaced the IAC and Throttle Position Sensor. Today I cleaned the throttle body and wiped the gasket off. It appears to be in good shape.

I also have a really loud hiss sound coming from the driver side of the engine bay. It sounds like someone using an Air blow gun. So im assuming I have a vacuum leak but I’ve check all of my vacuum lines on the top side of the engine and the appear to be in good shape.

Could a bad brake booster or Purge Valve Solenoid cause the loud air sound? It sounds about like the area it’s coming from.

 

[Travelin Ram]

Probably the brake booster.

Find the vacuum hose, disconnect it from the booster and plug the hose going to the engine. If idle goes down, there’s your problem.

*NOT SAFE to drive that way. You’ll have no power brake assist.

 

[pacofortacos]

High revs + hiss = vacuum leak. Usually a split hose or totally broken hard plastic line.

Brake booster would be rare.
Look for a broken vac. line, the vac. lines on the 4.7's get brittle and break and are hard to find. Usually not broken off but split - I have changed several on my son's 4.7 HO jeep.

Usually if it's a brake booster, you will hear it more inside the cab than outside.

 

[Krmcfarlin]

@pacofortacos ill go check them out again, I appreciate the response. Apart from the lines that run to the Purge Valve solenoid under the fuse box am I over looking any lines in that area?

 

[Krmcfarlin]

@Travelin Ram ill give this a shot, do you think that would have anything to do with the CEL as well? It threw a code for low fluid but the fluid was full and the codes gone now.

 

[18CrewDually]

I agree sounds like a vacuum leak. You can unplug one hose at a time and plug the manifold side of where the hose goes and see if the noise goes away to isolate the issue.

 

[pacofortacos]

@pacofortacos ill go check them out again, I appreciate the response. Apart from the lines that run to the Purge Valve solenoid under the fuse box am I over looking any lines in that area?

On the jeep there are several hoses in that area. Isn't the PCV valve hose on the drivers side? There were a few hoses on the back of the jeep behind the throttle body.
If you have a spray bottle, you can put water in it and while it is idling spray a mist where you hear the sound - it and the rpms should change when you hit the leak.

 

[Krmcfarlin]

So I believe I have found the issue. The EGR tube that goes from the Egr valve to the intake is leaking at the intake. I can see the blue gasket, when I push the tube in it runs fine but I keeps pushing back out. I’m thinking someone may have bent the tube? Is there any type of plate to secure it to the intake?

 

[Krmcfarlin]

Does any one have a picture of the EGR mounting bracket marked “1”? I can’t find one online send most pictures block it with the sensors on the throttle body. I have absolutely no hardware there just the tube pressed into the intake.

 

[jws123]

I have never seen a 4.7 have a mounting bracket like you show in pic just pushes in gasket kind of holds it in along with the 2 lower bolts on egr.

 

[Krmcfarlin]

I have never seen a 4.7 have a mounting bracket like you show in pic just pushes in gasket kind of holds it in along with the 2 lower bolts on egr.

You were correct. I went to the junk yard and got an EGR tube. The 4.7s don’t have mounting brackets. The tube I had was bent just enough to cause a vacuum leak because it wouldn’t go in to the intake far enough. Grabbed a new and put it on. It runs great again.