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2005 chevy trailblazer_ls
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6 Posts
Discussion Starter · #1 ·
Hey new to the site and from what I see there's a lot of good info here so hopefully you can help me out. I have a 2005 Trailblazer ,99,000 miles, which was coding for a bad ect sensor. So I replaced the ect sensor and the thermostat 192 degree while I had the alternator off. Flushed the coolant refilled and burped the radiator no problems. Temperature sits at 210 according to the less than accurate gauge in the truck, temperature gun says more like 196. No new codes since installation. However now at idle if you turn on the A/C or defroster (engine cold or at operating temperature) the engine rpms surge from 400rpms to 1500rpms back and forth. Throttle response is great and normal driving minus stopping is fine. Upon stopping the motor reinstitues the rpm problem followed by a somewhat confused transmission downshift or torque converter issue. Before changing the thermostat housing and ect sensor the vehicle drove perfect just a ses light on the dash now I wish I wouldn't have touched it. Is it possible that the computer is just trying to learn since I had the battery disconnected for so long? I've check for vaccum leaks or any unplugged connections I have a clean 13.1 V at the battery with my multi tester and no popped fuses in site. Thanks in advance.

BDBWTE
 

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2004 gmc
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26,181 Posts
Welcome! The computer is trying to RELEARN how to deal with a horribly gummed up throttle body. With no PCV valve, these engines gunk up like a toilet on the back side of the butterfly valve, and some members need to clean them every 30K miles.

The symptom that convinces anybody here that it's a cleaning issue is that it's worse with the AC on and the compressor cycling.

It's a miracle cure, you will be saying in about three hours. Less, if you have the TB cleaner in your shop supplies already. :D

http://forums.trailvoy.com/articles.php?do=viewarticle&artid=91
 

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2005 chevy trailblazer_ls
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6 Posts
Discussion Starter · #3 ·
Thanks for the quick reply I'm on my way out the door now to clean the Throttle Body it hasn't been touched since GM put it on I bet it is a site. :D
 

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2002 olds bravada
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2,369 Posts
I've check for vaccum leaks or any unplugged connections I have a clean 13.1 V at the battery with my multi tester and no popped fuses in site.
Shouldn't it be ~14.1 Volts?
 

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2005 chevy trailblazer_ls
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6 Posts
Discussion Starter · #7 ·
Thanks all cleaning the throttle body worked great. I should have taken a picture the back side was extremely dirty took sometime to clean it all but it idles great now. Probably need to do this every 50,000 or more hasn't idles this smooth for awhile. I get 13.1 volts sitting with the engine off with the engine on and alternator charging I read about 14.3v the battery is only 1 year old.
 

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2003 chevy trailblazer_ltz
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201 Posts
glad you were able to get it fixed..just had similar problem with mine, and it turned out to be a vacuum line disconnected on my TB..mine would surge then drop below 1000rpms, usually stalling the motor...glad it was nothing major, warranty paid for it all including new blower motor..
 
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