I've got an idle problem and was hoping for some help in understanding the throttle plate functions during warm up.

I've got an S5. I can't remember if there are two primary or two secondary throttle plates....but need some help in understanding how each one functions during the warm up process.

1) High RPM idle for 10-15 sec (around 3K rpm)-not important ...operates okay.
2) Drops to 1200 to 1500 (I've got an oscillation problem here that lasts for appox 1-3 min)
3) Eventually drops down to 800 rpm. Okay once warms up.

Read a thread from JKrueger that described my problem exactly ....he closed either the primary or secondary plates (need clarification here).

The secondaries, in my case seem to be open quite a bit..haven't found the spec on these.

Would appreciate your suggestions.

Thanks.

 

Look in the FSM on page F1-36. It shows the fast idle adjust screw. Use that to set the idle speed when the engne's cold (after the 3000rpm bit).

 

Thanks Jason. Maybe you can give me some tips here.

So I'm not just blindly making the adjustments, should I try to open or close the primary throttle valve? A couple of weeks ago, I tried adjusting that screw. I must have made at least 4 revolutions, I didn't see a difference. Nothing. What could I have been doing wrong?

The FSM says I should have 16 to 20 mils clearance at the primary throttle valve and the bore. I'm pretty sure I had much less than that. Used a 20 mil wire gauge and couldn't get the wire past the plate. Didn't have a 16 mil gauge. What makes sense here..opening or closing it? Opening...right? That's opposite to the thread that I read from JKrueger. He said that he closed down the gap...

If you do a search on "1200 1500", you'll see his post.

What do you think?

Thanks

 

I can really only tell you what I did. You'll see on the same page in the FSM there's a screw on the top of the thermowax rod. Adjust that as per the instructions before you set the fast idle speed.

I didn't measure the primary throttle clearance, I just started it cold and adjusted the fast idle screw until I got a nice 1000-1100rpm idle.