Idle question on my 92 3.6
 

Hi guys,

Just picked up my (new to me) 92 C2 Cabriolet and noticed that right at start up the idle goes up and down several times, ranging from 1200 down to 400 or so before settling in at 800 or so, after 5-10 seconds. After that it seems to idle fine. Is this normal? If not, what might be the culprit? The vehicle just had a lot of work done, complete reseal, immediate shaft bearing, major tune up, etc....

Appreciate any advise here. I'm sure I'll have many more questions for ya soon.

Sometimes mine goes right to 800, sometimes it hunts for a few seconds, so don't really know if normal, but not a problem for me.
You might try cleaning the ISV valve.

Yes, it might be the ISV, but it also might be the micro switch on the throttle bell crank. If for some reason the throttle hangs up a bit before closing completely, the switch might not be closing the circuit that tells the DME that the engine is idling.

Most recently had a problem with starting it. It was warm (ran within 30 minutes) but it took 10-15 seconds of cranking to get it to fire. It then "hunted" for an idle speed and ran fine there after. Very intermittent.....

Worsening vacuum leak?

Sounds like a lazy idle valve, they are easy enough to remove and clean, use carb cleaner, rotate in your hands, you should be able to hear it moving freely

Stupid question but what does the idle valve look like?

Ok, I think this is it? The silver canister on top? What do you do to clean it? http://forums.pelicanparts.com/uploa...1415397559.jpg

yep, 3 pin electric connection and and air In and out

Cleaning is pretty straight forward. Once you have the ISV in your hands, spray carb cleaner down the throat around the little vane valve. Your's is probably gooped up pretty badly with congealed oil and dirt. Technique is to spray the solvent down into the throat and then agitate the area with a small brush or tooth pick. You will continue to flush and shake the valve even after the valve appears clean. Used compresses air to blow out the vaned valve as well.

When you shake the valve do it vigorously. You are attempting to free up the valve which is frozen due to the gunk (technical term). Eventually, the valve will continue to "rattle". When the valve is fully cleaned, the vigorous shaking should produce a sound that is about the same sound you get when shaking a rattle can of paint. The paint can that has metal balls in the can to help mix up the paint (which is why they refer to these paint cans as "rattle cans"). It may take a half dozen solvent washes accompanied with vigorous shaking of the valve to get the ISV to begin rattling.

Finally, use compressed air to do the final cleaning of the valve before re-installing the ISV. This type of cleaning apparently restores most of the poorly operating ISV's out there.

Also, I have been advised that idle hunting is abnormal. It can be a lazy ISV as Bill V. suggests. So, clean the ISV first. If the hunting continues after you clean the ISV, then you should check for a vacuum leak in the myriad of vacuum lines installed on your engine.

Extremely helpful, thank you. I'm going to try today.

Ok, removed it and it has a slight rattle. Feels like it's moving maybe 1/16" inch when shacking it up and down. I have cleaned it 4 time and doesn't seem to increase the rattle. I'm going to leave it soaking full of carb cleaner for a while. How much should it move when shaken?