IAC Vavle, how much should it move?

[c-72]

I have a 1993 S10 Blazer with the 4.3L Vortec engine and I think that my IAC vavle is bad. I took it out and cleaned it and it ran good for a few minutes, and then it went back to a rough idle. So I was wondering how much the post in it should move up and down. The one in mine barely moves at all. Thanks

[c-72]

bump...

[jsgold]

I have a set of GM manuals for the 93 and it does not give that information. I have dealt with them enough though to tell you they don't move much. You should NEVER squeeze the spring or try to adjust it in any way. On other GM cars such as my Corsica it does give the normal length of the assy. but never gives amount of room they move. For the record, I have a 93 and based on my truck and the service manual you could have a vacuum leak, sticking injector, dirty area around the IAC, crankcase vent valve, etc. and you might want to check your EGR valve. They get carboned up quickly. I assume you have good plugs, wires, distributor cap and button? When was last time fuel filter changed? ALL of these can affect idle. Most recently my 93 had a vacuum leak that caused erratic idle. You can check the IAC with a special tool, but not something most people would have(IAC TECH 1 scan tool). Chances are, if it is moving, it is OK. Clean the area it sits in, spray some injector cleaner in the intake area, make sure of the wires, plugs, and vacuum lines. Buy a EGR gasket, remove and clean the EGR. Be sure to reset the IAC. When you hook up battery start the truck and let it idle on its own for 5+ minutes. Do not give it gas. It has to be reset by the computer. If this does not work check for leaky injectors. In fact, check you oil for a gas smell just in case. Would mean new injector spider assy needed. Other ways to check as well. Plenty of information here on THAT. Very common problem....

[blazer94]

Originally Posted by c-72

I have a 1993 S10 Blazer with the 4.3L Vortec engine and I think that my IAC vavle is bad. I took it out and cleaned it and it ran good for a few minutes, and then it went back to a rough idle. So I was wondering how much the post in it should move up and down. The one in mine barely moves at all. Thanks

jsgold gave very sound advice in determining what could be the culprit. Here is what I have found in dealing with my iac. The movement is not what is measured, it is the distance that the pintle extends from the mounting flange surface. The distance is not to exceed 1-1/8 inches. These IAC'c can be adjusted, and the info is in the Haynes book. I gathered the info on the iac from the friendly tech at dealership.

[rksnc]

You can check IAC resistance if you want. With the lock tab in up position. Measure resistance between a&b - c&d....A starting from right to left with lock tab up. Resistance should be 40-80 ohms
Then you can check from b&c---a&d, resistance should be infinite. Now again that is the connection with flat plug and lock tab pointed up.
You can also turn engine off, ground terminal b, wait 45 seconds ,then disconnect iac, crank engine, if rpms greater than 800 there is a vacuum leak.
With scan tool you could watch iac counts and see better as to what is going on. 0 counts would be vacuum laek, high counts could be from running rich.

[c-72]

Thank you, I wil check all of those things within the next few days. I was also wondering if it is possible that a vacuum leak in the 4 wheel drive line cause cause a rough idle? Could it be tied into the rest of the vacuum lines?

[c-72]

And also what do you mean by button?

[jsgold]

I was referring to the rotor cap. Sits under the distributor cap. I have heard it called rotor button and call it that out of habit I guess.

[c-72]

I got it running fine now. It seems as though it was the EGR valve. So for now I am bypassing it until I can get a new one. It looks like they are pretty expensive, around $160.00.