Question about Chevrolet Blazer

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My brother has an 2004 trailblazer he put in a new thermastat and after that the blazer still runs great but now when ever you turn on the fan motor for heat or air . the idle drops down to like 300 or so rpms and it stalls .runs very bad only when using the fan motor controls . the chevy dealer and gm themselves dont know and have had it for days .revamped computer and tried different stuff ,any help would be great .

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  • Ryan Lutton
    Ryan Lutton Jul 18, 2017

    Dennis, this sounds like an easy fix. Was the battery disconnected when the T-stat was put in?



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If it is the IAC valve, or even if it's not because the vehicle is more than 14 yrs old, remove IAC and clean with MAF sensor cleaner...remove all carbon, spray liberally on spring and pintle and inside pintle access, do not touch with bare hands, wear rubber gloves and wipe pintle in a straight forward movement. Do not turn pintle, if you do by accident, it will readjust on it's own, but will take a while longer...cheers..

Note: when done and reinstalled, let engine run and Idle for about 15 minutes to readjust properly...

Posted on Jan 21, 2018

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Hello Dennis,

Is this only occurring at Idle? In other words, if at speed, you turn on fan ac controls and it runs fine (until you return to idle such as at a stop light)?

If so, then I would suspect the IAC (Idle Air Control) valve. When you turn on the fan control and the compressor kicks in, the IAC circuit is supposed to maintain the engine idle.

I recommend checking the IAC valve first, then let us know your findings.

Posted on Jan 21, 2018


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SOURCE: low idle stalls out

Here is the most common cause of surges and stalls at stops and low erratic idle speed and rough idle, it is the idle speed control air-bypass valve and throttle valve (IAC for short), they get full of gunk over the miles and cause idle issues (stalls, low idle) like yours, Get a can of intake cleaner from any local parts store, not carb spray, intake cleaner, it is made by a company called CRC, remove the air intake hose to the engine, hold the idle high so the engine won't stall, then spray the can of cleaner into the intake while keeping the engine running, use at least 1/2 the can, shut down the engine and disconnect the battery for 5 minutes, then restart and complete a number of mixed driving cycles, town, freeway, stop and go etc., after a few days the problem will go away as the system will relearn to the clean intake.

Posted on Mar 13, 2009

  • 718 Answers


Chevrolet 2004 TrailBlazer

Look next to the blower. You can remove the panel under the passenger side. Go through the glove box and move it down out of the way to access the electrical connector. Then remove two bolts and the electrical connector.

Posted on Apr 21, 2009

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SOURCE: when i turn on my heat my 2004 trailblazer stalls

if this happens while the defrost of ac is turned on, it could be a seized ac compressor which will cause the serpentine belt to squeal and drag making the engine sometimes stall. if it happens with the ac off and the selector on say the floor, or dash vents, the issue could be a bad alternator and battery. this is confirmed when the blower motor engages and the lights dim and then the truck goes dead.

Posted on Feb 17, 2010

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SOURCE: 2006 Jeep Cherokee 3.7 V6 2WD almost stalls when idling

while idling the jeep is cleaning its self<!-- from fixya rte -->

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SOURCE: 2004 TrailBlazer: what size tire fits a 2004 chevy trail blazer...

Typically it is a 255/65R/17 or 255/70R/17

Posted on Oct 26, 2010

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