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Hey Cam Got another one...
Hey Cam Got another one for for..
Submitted: 8 months ago.Category: Chevy
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Customer reply replied 8 months ago
Ok I have had this issue for 3 years. Been Diaging it since. When the cooling fans turn on at 223 like there supposed to if you keep your foot in it sitting still for another Minuit at 2500 rpm it will take over by itself and run idle up to about 3500 by itself. If you turn off and restart it is fine until it gets back up in temp. Had a GM tech look at it in 35 years hes never seen one do this. and he sees no evidence of anything on scanner. Now he never had scanner plugged in while it did this. Theres no codes no air leaks fuel pressure is where it should be with no fluctuation at time of it. Throttle body cleaned new IAC New computer Checked for updates for it and its current. I think its electrical. Because when it did this once before the cooling fans relay started clicking fast like it was confused. Wiring to fans has been tested new cooling sensor and plug both cooling fans are fine... Geesh Im lost..
Answered in 1 day by:
9/16/2017
Chevy Mechanic: Jerry Newton, Chevy Technician replied 8 months ago
Jerry Newton
Jerry Newton, Chevy Technician
Category: Chevy
Satisfied Customers: 5,633
Experience: ASE Master Technician, L1, Master GM Technician. Over 20 years of bumper to bumper GM experience.
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I'm not sure what you mean by "keep your foot in it" at 2500rpm. Are you holding the throttle open at 2500rpm?

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Customer reply replied 8 months ago
just keep it at 2500rpm in park for another minute.
Chevy Mechanic: Jerry Newton, Chevy Technician replied 8 months ago

I guess I'm not clear on why you're holding the throttle at 2500rpm, and then the engine speed increases to 3500rpm? Does it stay there if you release the throttle?

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Customer reply replied 8 months ago
This vehicle turns the fans on at 223 degrees via the computer when you are sitting in traffic with it and it turns the fans on on a hot day it still gets a little warmer before it starts cooling down as that happens if you were sitting in traffic the throttle will automatically raise the idle on its own to where you cannot practically hold it with the brake running it up to approximately 3,500 RPM by itself until you have to shut it off I was diagnosing a cooling fan issue thinking it was something with those but since I've pinned out all the wiring and everything seems fine there I believe it has something to do with an electrical issue causing the IAC to adjust the reason why I say about sitting there and running it at 2,500 RPM is to get it warm enough so that I can get it to do what I'm trying to fix
Customer reply replied 8 months ago
I have only found one other person having this problem with their GM and there was no response to their question of why there's does it also so it doesn't sound like a common problem but it does sound like there's more than just me out there that has this at the time
Chevy Mechanic: Jerry Newton, Chevy Technician replied 8 months ago

Ah, OK. I got the impression you were holding the throttle open with your foot.

Did you replace the IAC electrical connector pigtail when you replaced the IAC?

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Customer reply replied 8 months ago
No I did not replace the pigtail
Chevy Mechanic: Jerry Newton, Chevy Technician replied 8 months ago

I have run into numerous issues with broken wires inside the IAC connector. Because the IAC doesn't feedback to the engine computer, the computer doesn't have any idea whether it actually moves or not, or if the wires are even connected. Because of the way this motor works (stepper motor), if you have a broken wire, the IAC can move in one direction and not the other, and this can be very intermittent.

I would replace the IAC connector just as a preventive measure, if you are having issues with high idle, this is a very common problem. However, it's not related to the fan, temperature, etc.

Do you have a scan tool that will read live data so you can watch what is going on?

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Customer reply replied 8 months ago
I can watch the live data I have a modis. I can control the IAC up and down with my scanner but when I had it at the GM garage the tech plugged in his IAC controller and it would not move the IAC up or down in RPM so he said to replace that which I didn't think was the problem because I could move it with my scan tool but I replaced it anyway
Customer reply replied 8 months ago
I thought it originally had a cooling fan issue because at 223 degrees on this specific Aztek it is at the line right before red on the gauge so I was thinking it was a cooling fan issue but since I have done more research I'm pretty confident that it is not it but I did take and do a test of my own by plugging a new IAC in and ran it till it got to the temperature that it backs up at and it looked like to me that the computer didn't know what to do with the IAC because the pencil jumping in and out. I believe I also noticed at one point that when it starts doing this that the relays for the cooling fans start jumping erratically making contact as a clicking fast and irregular not staying steady like they are confused
Customer reply replied 8 months ago
New IAC didnt work..
Chevy Mechanic: Jerry Newton, Chevy Technician replied 8 months ago

The time to diagnose this is when it acts up. When it is acting up, what is the IAC doing, and what are the other data lines doing? There has to be something in the ECM data that will reveal the root of the problem, is the data getting screwy or out of the norm, or anything like that?

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Customer reply replied 8 months ago
Everything I can check has been done. Off to a auto electric shop..
Thanks
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