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2004 gmc envoy_sle
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Discussion Starter #1
Hi, my envoy 2004 RPM needle will move up and down when i turn on the blower/vent or the a/c, and the engine will rev like its about to stall. what can be the cause of this? i tried to google it i found something about "IAC" idle air control valve, this might need cleaning or replacement. any suggestions and advise will really be appreciated. :)
 

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2004 gmc envoy_slt
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56 Posts
i tried to google it i found something about "IAC" idle air control valve, this might need cleaning or replacement. any suggestions and advise will really be appreciated. :)
Welcome Raj!

I'm still new here, and just getting to know my Envoy.

Please fill our your profile, so we know what model, engine, year, etc. you have. Help us, help you. :)

Because of the electronic throttle body, I would think the I6 engine doesn't have a IAC. Yet, that's pure speculation.

Have you cleaned your throttle body?
It's a simple operation which improves your engine performance and saves 3 baby penguins for ever 1,000 miles driven.

Have a great day!

-- AJ
.
 

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2004 gmc envoy_sle
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Discussion Starter #4
Thanks for the advise, so the Vortec 4.2L.I6 do not have an IAC? so i should clean the "Throttle" and could possibly fix the engine rev when i turned on the vent/defroster/ac?
 

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2004 gmc
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26,181 Posts
There is no separate IAC. The main throttle body contains the only butterfly valve in the design. And the back side of the tube gets horribly dirty with crankcase gasses and then the butterfly valve sticks.
 

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2004 gmc envoy_sle
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Discussion Starter #6
Thanks alot, im going to clean my throttle body and sees if that really fix my problem. :)
 

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I had what sounds like the same problem on my 02 TB last year. The problem ended up to be the water pump. Sounds kinda crazy but it was explained to me that the computer is sensing the extra "drag" and getting confused trying to compensate.

Easy enough to check, just take the belt off and see if the water pump pulley moves up and down indicating a worn bearing. I did that and found the bearing was worn.

Replaced the water pump and the idle went back to normal.

Surprised me.

Good Luck.
 

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2004 gmc envoy_sle
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Discussion Starter #8
I did clean the throttle and the when i turn on the a/c or blower it work fine. now my envoy won't stalls or the rpm needle moving like before. thanks again guys for your advise.

 

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2006 chevy trailblazer_lt
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Could also be....

I had the same thing on my 2003 Trailblazer after I had a starter put on. Turned out that they left the battery unplugged too long and my computer lost the data that controls the rpms. Had to have a dealer reprogram it for $100.
 

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I had the same thing on my 2003 Trailblazer after I had a starter put on. Turned out that they left the battery unplugged too long and my computer lost the data that controls the rpms. Had to have a dealer reprogram it for $100.
Knowing what hundreds of members have reported here over the years, I think the dealer was blowing smoke at ya. The vehicle can go MONTHS with a dead battery and still remember how to run. Only a bad PCM would lose its memory as quickly as yours (if that was the true root cause), and that would be covered as a free federal emissions repair up to 80K miles.

What goes bad with a battery disconnection is the experience data of how the computer deals with a dirty/sticky throttle body. The computer seems to be able to handle a throttle body that slowly grows dirty, until it reaches a threshold at 30-50K miles and then starts to have erratic idle when the AC compressor cycles on or off.

If the dealer didn't clean your throttle body for your $100, you should read the article and schedule doing it yourself for $5.
 

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2006 chevy trailblazer_lt
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Thanks!

What he told me was that most will "re-learn" but that my 2003 model was one that would not. It was bad too as the rpms would go up and down, then the car would die on the road. When I picked it back up at the dealer, it worked fine. Maybe he just cleaned that throttle body alone. He said that was included. However now I have had a ticking that they said was the fan clutch. This evening I barely touched the gas pedal and the rpms rev up to 2000 to 2500 and it sounded like am airplane throttling up! Guess it is time to finally get the fan clutch replaced. I have a small garage that said they could do it.
 
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