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Discussion Starter #1
I have a 1994 Chevy s10, I am having an idling issue and I checked all my sensors to make sure they were getting the correct operational voltage after replacing them with new ones. All of them except my O2 sensor is getting the correct voltage, it’s supposed to be getting (.5 volts) in the signal wire with with key turned on. It’s only pulling a (.17). In trying to figure out what is going on because I think this is where my idling is issue is coming from. I’m trying to figure out if it’s my wire or maybe it could be my computer that has failed. Any suggestions?
 

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The signal from the O2 sensor is a voltage, and it varies. With the key on, engine not running, it should level out at a low level, around 100mV more or less. Sounds like yours is working properly.
 

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Discussion Starter #3
So with the engine running is should fluctuate from 100mv to 900mv correct? I though it was supposed to be around 500mv with the key on. But idk, I have a new O2 ready to put in and see what that does
 

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So with the engine running is should fluctuate from 100mv to 900mv correct?
Correct. It's a voltage source that is based on the presence of oxygen. Oxygen present makes it 100mV. No oxygen present and it will be 900mV. With the engine not running, oxygen (fresh air) will work it's way up through the exhaust system and make it 100mV due to an oxygen rich atmosphere at the O2 sensor.
 

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Discussion Starter #5
I seeeeee, I’m going to just replace my O2 and see if that helps, the idle is only bad when my truck warms up
 

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If the O2 sensor is oscillating between ~100mV and ~900mV when it's running, it's working right. If it cycles at least once a second, a new one isn't going to change anything.

Is it misfiring? Stalling? only at idle? or at all engine speeds?
 

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Does the idle RPM wander? Drop sometimes, other times surge a little high? Sometimes drop enough to stall out?

That's the symptoms of a clogged idle air passage in the throttle body. Get some throttle body/intake cleaner and thoroughly clean the small passage next to the throttle plate. You should also remove the idle air control valve and thoroughly clean the bore where that valve sits, and clean the plunger on the valve itself. You usually don't need to replace that valve unless you bend or break the plunger trying to clean it.

That might not be your only problem, but that's where I start when I've got random stalling at idle. No matter what, I'm pretty sure yours is dirty.

Any further diagnosis and suggestions will depend on whether you have TBI (RPO code LB4, VIN "Z" if I remember right) or MFI/CPI (RPO code L35, VIN "W").
 

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Discussion Starter #10
I have replaced the IAC about a week ago and I done that exact thing, I sprayed it where the IAC screws in to the TBI (Z) I also replaced my TPS and CTS which had gone bad.
 

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Discussion Starter #11
Just replaced the O2 sensor and it’s working properly but still has the surge in the idle and eventually chokes, I’ve done absolutely everything I can think of, I’m absolutely lost, not to mention I’ve taken it to mechanics and they’ve all just scratched their heads
 

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Did you clean the passages in the throttle body? The idle air passages that lead to the IAC valve? You might have a bad IAC valve. When you replaced it, did you use a genuine GM part? Or aftermarket?


You should also check for vacuum leaks.
 

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Discussion Starter #13
I sprayed injector cleaner in the valve but it was just hitting the inside of the TBI, I replaced it with a AC Delco, and I’ve looked everywhere for vacuum leaks
 
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