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Discussion Starter #1
Hey guys,

I've been fighting a rough idle for quite some time now. I figured it might have a vacuum leak (I'm hearing a very loud hissing near the throttle body area), so I thought I might as well use my handy dandy ebay smoke tester I used for my sisters 08 mustang lean codes (worked great). I replaced all the vacuum lines quite some time ago, and visual inspection did not reveal anything substantial.

Anyways, I saw a few puffs of smoke coming from the side of the throttle body where is the spring and linkage is, and huge streams of smoke coming from this hole under the throttle body, near the throttle position sensor. If you look at the front of the throttle body, standing from the passenger side, it's under the right side. I see there is a hex bolt and o ring under it, and it's pretty loose when I touch it (I can feel it rocking back and forth). What exactly is this screw? Does it have anything to do with the tps? I can't find anything about it in the service manual. I don't see how smoke coming out from it would be normal. Can I just snug it up? Or will it disturb a preset adjustment?

Any guidance would be most appreciated!
 

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Is that Blue tape holding the intake on? and is that a snake under it... :eek:
 

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Might be worth picking up another used throttle body. Someone on here might have one, or check on Car-Part.com--Used Auto Parts Market

A vacuum leak should just produce a high idle. A rough idle in my experience points to possibly an EGR valve stuck open.

Al
 

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Discussion Starter #4
Very funny...that's shop towel stuffed into the throttle to keep crap out, and that snake.... well it happens.

Anyone happen to have the powertrain/emissions manual? The shop manual references this bolt, but directs you to the powertrain manual. It wasn't in the zip file that was posted a while ago.

The EGR is fairly new, and was not stuck open when I tested it. Spark is good at all 8 plugs, plugs and wires are newish (replaced recently). Smoke test did not reveal any other vacuum leaks. The thing is, if the EGR was stuck open it would act as a vacuum leak, so a large vacuum leak at the throttle body would have a similar effect.
 

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The bearings that support the shaft for the butterfly have a a silicone seal; the ones in the imrcs in the dohc b heads I have were wasted, and that could be it.

You can get new bearings from VXD, if I remember correctly.

Note: I am snake friendly. :)
 

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Discussion Starter #6
Sorry for the late update, I have a habit of not concluding my posts. Too busy with school.

Anyways I marked it with some paint in case turning it screwed up some delicate setting, and tightened it. No difference in the engine running, I'm still trying to diagnose my rough idle. Might just make a new thread.
 
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