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Discussion Starter #1
My truck is throwing a code for a vacuum leak, and the idle drops pretty frequently when I'm sitting still. I looked around under the hood while I was changing the thermostat, but I didn't see anything that looked like it could be the problem. Are there any usual culprits on our trucks? Its a 2004 i4, base model. It's had this problem since I got it which was about two months ago.
 

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check your resonator hose up top. our engines are what they call a closed orifice system. there is another hose also that requires full replacement of the intake manifold. common problem. had mine done at the dealership. cost me about $600 .
 

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^^^Yes^^^

Also, vacuum leaks can be tough to troubleshoot as it could be anything from a pinhole to hidden crack (dry rot). One of the easiest methods to locate is have your truck checked for leaks at a service ctr...cheaper than going out and purchasing necessary equipment to determine the cause. I let the experts find it...not as easy as the old days when hoses simply broke in half. Good luck.
 

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Discussion Starter #6
check your resonator hose up top. our engines are what they call a closed orifice system. there is another hose also that requires full replacement of the intake manifold. common problem. had mine done at the dealership. cost me about $600 .
Do you have a picture or diagram of where the resonator hose is?
 

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Discussion Starter #9
Alright I checked the resonator hose and it looks good. I checked other possibilities around the throttle body and intake and I can't find it at all. So, I have a question. Is it common for the intakes to leak on the 2.8?
 

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That P0420 code is a catalyst efficiency fault that can be triggered for many reasons.

The P0520 code is for the idle air control (IAC) system rpm lower than expected during cold start up.

What makes you think there's a vacuum leak?

Is this a stock engine with no bolt-on mods?
 

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Discussion Starter #14
That P0420 code is a catalyst efficiency fault that can be triggered for many reasons.

The P0520 code is for the idle air control (IAC) system rpm lower than expected during cold start up.

What makes you think there's a vacuum leak?

Is this a stock engine with no bolt-on mods?
The little print out Auto Zone gave me with the codes both had Vacuum leak listed as the issue. That's why I thought that.
 
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