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Discussion Starter · #1 ·
Intermittently when I'm driving my S4, the idle won't drop down below 2k rpm. Happened last night, the first 10 minutes of driving was fine, then as I shifted and drove through back roads and stopped at lights etc, the idle wouldn't drop below like 1900rpm. After about ten minutes of that, it went back to normal and was fine the rest of the ride. I even tried to reach down and pull the gas pedal up like maybe it was sticking, but no change. Oh and I do have the throttle jack disabled and removed, and I did not get a check engine light. Not sure if it's mechanical like the cable is somehow sticking sometimes or if it's maybe the butterflies sticking? Or maybe it's a normal condition that can sometimes occur. Thanks in advance for any comments.
 

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I had a similar problem. It was primarily because the throttle cable was too tight. The slack in the throttle cable changes as the engine heats up, so when it gets hot the cable does not allow it to return.

Not sure if it helped, but I also made a small wooden block with a groove in it, and attached it where the cable makes a sharp bend going into the cable adjuster stop at the engine. That sharp bend bothered me, and the block just gives it strain relief so that it doesn't kink.

Don't overtorque that cable adjuster. Its easy to break. You can guess why I know.
 

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Discussion Starter · #3 ·
Thanks for the info. I removed my IAC and checked it and it seemed clean and working. Then I spent the better part of yesterday adjusting my throttle cable to make sure I had some slack in it - it had no looseness at all. I adjusted both the pedal end and the throttle body end. Turns out I had to adjust both ends way in(out) so I had some slack, then messed with the full throttle opening by adjusting the bolt on the gas pedal back and turning that in. I figured a way to use a long adjustable pole to push on the gas pedal as I was near the back of the car and then look at the throttle bodies to make sure I got full opening - I know, kinda jury-rigged but it worked!
 

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There is no way you can properly adjust the cable or base idle without a scan tool. You can download Freescan and get a cable from Sanj. The whole deal will cost about $100, something you need to have available.
 

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Discussion Starter · #5 ·
Are you talking about checking the IAC counts at idle using a scan tool?

And then checking the TPS for 100% throttle opening?
 

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Yes you should use freescan to make sure you get 0-100% with the throttle, but you do need to leave some slack for the enging expansion due to heat. Adjust the throttle while the engine is hot.

As far as the idle goes. You cannot adjust the idle, the ECU controls that via the IAC. Do not try to adjust it by ear, and freescan will only set the idle temporarily for diagnosis purposes. If you want to check your IAC, connect freescan and allow the engine to idle up to full temp at ~80C coolant temp. The IAC counts should be between 20-40. Otherwise you may have an air leak or other issue.
 

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+1 on cable adjustment.
It took me a long time to get everything right, I was amazed by how much the cable tightened up after the engine was fully warmed.
There are 4 adjustment points that all need to be in the correct balance...

Cable adjustment at the throttle body
Cable adjustment near the pedal
Pedal "Up" travel stop bolt
Pedal "Down" travel bolt (I removed mine altogether for max legroom)

The trick was to set the up and down limits to allow enough deflection for 0-100% throttle, plus a little extra, then work the cable adjusters so I could get 100% throttle with the engine hot without causing undue strain...very finicky.

My car was missing the heat shield over the cable when I got it. I replaced it and found that it does help decrease the heat expansion a little.

I also added a (4" long) piece of PEX tubing to the end of the adjuster near the pedal to reduce friction from rubbing on carpet. I just force-threaded it over the exposed end of the adjustment screw, guides the cable nicely.
 
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