air bypass valve?

[echo]

Curious about what the air bypass valve is suppose to do. I noticed that my 87 was idling rather high even after being warm. Just a blind guess I unplugged the bypass valve and the idle came right down. Of course the next morning it wouldn't start well without it plugged in. Are they suppose to work like an electric choke? Are they known to "stick" like this or is it something else?

 

[RustedRanger]

It's a "controlled air leak" to adjust the idle....GM calls it an idle air control valve. They can stick....there are tons on threads about this. Mine had so much gunk in the intake ports for the valve that it fouled the plugs when I sprayed it out. My valve got worse after I cleaned it so I replaced it but some have had em run better after cleaning it out. If you need to get a valve check rockauto.com....way cheaper than the parts stores.

 

[echo]

Yeah I figured it might be out there somewhere, but with over a hundred pages in the 2.9 section alone figured it was easier to just ask. Thanks for the info. I'll take mine off and clean it out then go from that. Have had some amazing luck with this truck so I hope it keeps coming that way with this to. I'll respond with the results.

 

[RustedRanger]

There is a search on this site. Remember to "blank" the computer memory by unhooking the battery for at least 10-15 minutes when ya change something so it can re learn.

 

[echo]

I plugged in a second air bypass valve while the engine was running to see how they work. Are they suppose to work like a little air pump?

 

[chazzone]

They don't work like an air pump, they are simpy an air bypass that allows the engine to start and warm up.

 

[kimcrwbr1]

The idle air control IAC controls engine idle I am not sure what your calling the bypass valve is it controlled by a wire connector or a vacuum hose maybe give us a pic.

 

[kimcrwbr1]

Pull the codes it could be your ECT engine coolant temp senser not telling the computer the engine is warm and just running at high idle.

 

[echo]

Here are the pictures of the item in question and a page from the manual where I got the name from. As for pulling codes I don't have the equipment available to do it. That's why I'm trying the old fashioned way.

 

[echo]

and it is controlled by a wire not a vacuum hose. Sorry the one pick is upside down. It's just there so show I wasn't making the name up.

 

[chazzone]

You don't need a code reader to get codes on these. Here is a link to procedure.

http://www.therangerstation.com/tech_library/OBD_I.html

Throwing parts at a problem and guessing doesn't really make sense when you have a system that will so easily tell you what is being affected.