My 96 (2.2) has had a low idle problem for about 2 weeks now & with help from a guy at work I found out what is causing it. It happens every so often & didn't have to be during any certain conditions. Today when the idle was low again (approx 300, then died) I pulled the vacuum hose off from at intake & re-started the car. The idle was up about 750, then I re-connected the hose & the idle dropped again. I unplugged & re-plugged several times & this is the problem. I asked the Dealer for the vacuum operated valve & he said they only sell it with the entire throttle body. He called it a "Idle Valve".
Does anyone know exactly what it is called & where I can get just this part? I have looked on line & can't find just this part.

 

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It's actually called the "throttle opener". I think it prevents the sudden closing of the throttle after high rpm operation such as hwy driving. It's just a vacuum operated dash pot. It is adjustable with a screw at the back and it appears that the vacuum overrides a spring on the valve. I think the increase in idle you are getting w/o vacuum is the action of the spring and/or the vacuum leak you create when you disconnect the hose. The adjustment rpm for the valve w/o vacuum after running at 2500rpm is 1300 - 1500.

I don't think your idle problem is that valve however. Usually idle problems are IAC or EGR. I would do a search andtry that first.

 

Thanks for the reply but, the problem I have isn't high idle, it's LOW idle. When the low idle problem happens I see the dash pot pulled away from the throttle linkage about 3/16 inch & the idle is about 300 then the engine dies. I can then unplug the vacuum to the dash pot, start the engine & the idle will be about 750 (close to normal) because the spring inside the dash pot pushes on the throttle linkage. I can then push the vacuum hose on & take it off the vacuum port on the intake manifold & watch the dash pot pull away from the throttle & the idle drops. I can do this over & over again & the same thing happens. I drove around yesterday doing my normal shopping with the dash pot disconnected & vacuum port plugged & the low idle problem isn't there. With out this dash pot hooked up & working normally the idle very's from about 700 to 950 rpm's each time I bring the throttle back to idle (the idle doesn't very as it idles, but it comes to rest at a different rpm each time), so I need to get a new dash pot.

 

If the throttle valve was not working it would behave the same with or without the vac line. It's just a dash pot with a rubber diaphram inside operated by vacuum. It stops working when the diaphram leaks. Low idle problems can result from EGR and IAC. I believe you are using the throttle valve to compensate for improper idle caused in the IAC or EGR. The throttle plate should be closed when your foot is off the gas pedal. Idle air is controlled by the IAC. When was the last time you cleaned the IAC?

 

I bought the car 3 weeks ago & to get it smogged the place I got it from had to do a complete tune up & the IAC looks brand new too. The TPS also looks new. When the problem occurs my scanner reads the TPS at 14.4% at idle and it's normally at 12.2% at idle when there is no problem. The timing goes from 5 deg at idle to about 14 deg at idle when it occurs also. Both O2 sensors go up to about 840 & stay there while I have the low idle problem and a guy at work say it's because the throttle plate is closing off too much & choking the engine. I'm a diesel & chassis mechanic & rearly work on gas engines so I went to the best gas guy we have. We work different shifts so he really doesnt have time to look at my car, besides if I can figure it out I know it will stick in my head better then someone else doing all the work.
I understand what you mean about the dash pot holding the throttle up when there is another problem so I wouldn't notice this other problem. I'll have to find out about the throttle stop & see if that is changed from oem settings & maybe get some parts (dash pot, IAC, etc...) from another car & test them on my car.
Maybe the shop that did the tune & smog work messed with the adjustments of the dash pot (and other things) so it would run smooth & pass smog with a problem it has & now the problem is worse or better & thats why it's running different for me.
When the problem first came up I used a throttle body spray in the butteryfly area but I didn't know where the IAC port was until later when I read the manual I got for it. Should I pull off the IAC to clean it or just spray into the throttle body area while it's running. I originally sprayed the throttle body with the engine off, because thats what the can said to do. I wonder if sediment settled in the IAC port & could be making it worse?

 

I'm going to go through the steps of testing the IAC & TPS the way my manual says to before I start swapping or changing parts.

 

The throttle opener dash pot keeps the throttle slightly open when the engine is OFF. When engine is started the rod should retract via vacuum and not effect throttle position.

When you pull off the vacuum hose (engine on) the rod is being allowed to force the throttle valve open, this should only be occuring when the engine is off (no vacuum to dash pot). It sounds like the dashpot is working OK.

The idle is controlled by the IAC valve.

 

Thanks for the info guy's. I think I need to check the adjustments of each item during the testing of each item.