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Discussion Starter #1
I got a 1989 s10 4.3 has a good and bad idle. One min it will run great then the next it will drop idle low. You can be sitting at a red light and it will idle down low. Then all of a sudden it will jump up in idle and trys to take off. Then idle fine. So what have a done/changed. Lets get started i rebuilt the whole throttle body including new pressure regulator spring and new injectors. New idle control valve. Throttle sensor. New computer. New EKG valve.. new plugs.. wires cap button. New fuel filter and pump. So what could be going on that i have not already checked. Any help would be great
 

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94 4x4,01 Blazer
2001 Blazer 4dr 4wd LT
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you sir have a vacuum leak.
 

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Discussion Starter #3
All new Vacuum hoses. I put new on it because a few was brittle. So i thought the same thing Vacuum leak replaced all vacuum hoses. And still the same and none are plugged either. Ive been fighting with this case for 4 months now.
 

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Discussion Starter #4
It also has a new O2 sensor and knock sensor. And fuel pump relay. I just just been throwing money at it. And im staring to think that's what it likes. But it does have 300xxx miles. And i bought it for my dad 11 years ago and nothing was ever done to it. Till he passed away and it just sat for almost 2 years.
 

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I would say EGR might be an issue but also the fuel pump ground is known to rust and corrode. If you could get a fuel pressure gauge hooked up and check it in a low/bad idle situation, that could help rule out any issues. Do you have a volt meter? An old alternator and old battery will slowly go bad and put out less amps at idle. If you have dying alt and old battery plus poorly grounded fuel pump, you have a recipe for disaster. Otherwise I would start replacing all of the cheap sensors or at least consider testing them.
 

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Discussion Starter #8
Battery is new. When its running it puts out 14.43 volts even when it idle down. The fuel pressure is 13 and holds when runing and holds when off. The fuel pump was replaced and ground was good. Its act like its missing a little too.
 

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Discussion Starter #9
So it's still running decent. While driving but. Ever once in a while it still idle down and will run thatway for a min then idle back up. The high idle part has gone away. Could it be something electric im over looking. Like i said above i pretty much replaced any and everything that has to do with fuel related. All hoses was rechecked and mad sure they are running to the right part.
 
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