Intermittent high idle and whining sound

[JIMMYRIG]

I'm getting high idles and a whirring/whining sound (maybe vacuum leak) plus bad throttle response. It used to just happen after freeway driving, now its as soon as the truck is warm and gets worse after driving. Idles at like 2k sometimes after sustained freeway driving. I've chased all the vacuum lines and sprayed with brake clean, I had a thought it could be brake booster, maybe IAC (although its new and made no difference unplugged), or cracked intake/bad manifold gasket. Any ideas?

[hgeranium]

5 hours ago, JIMMYRIG said:

I'm getting high idles and a whirring/whining sound (maybe vacuum leak) plus bad throttle response. It used to just happen after freeway driving, now its as soon as the truck is warm and gets worse after driving. Idles at like 2k sometimes after sustained freeway driving. I've chased all the vacuum lines and sprayed with brake clean, I had a thought it could be brake booster, maybe IAC (although its new and made no difference unplugged), or cracked intake/bad manifold gasket. Any ideas?

I've had bad IACs out of the box. 2/3 of the new ones I've bought have been like that. Manifold gasket could always be a culprit. If you haven't tried, tighten the bolts. What do you have? 2.5? 4.0? Renix or HO? Your course of action can change based on this.

 

Is your EGR hooked up or plugged correctly? I had a similar high idle issue and something that seems to have helped fix it was a new EGR gasket. Mine was totally toast.

 

If you have a renix, the MAP to TB vacuum line is especially important. Cruiser54 has a tip to improve it.

 

Also worth checking your throttle body gasket and also making sure the throttle plate isn't getting physically stuck by debris. I would take the TB off, clean it, and replace the gasket. Especially clean the IAC port.

 

Just a few starting points, I'm sure others will have much more to say. Good luck!