Engine stalls when A/C compressor engages

Tiny
COORDINATOR15
  • MEMBER
  • 2004 CHEVROLET TRAILBLAZER
Six cylinder two wheel drive automatic 65,294 miles.

My vehicle has been great with normal maintenance. My battery was hard cranking and needed to be replace, so I stopped by the local parts store and bought a new battery last weekend and replaced my battery.

Here is where the problem started: that night after changing my battery, I went to use the defroster. When the A/C compressor engages at idle in park or neutral every five to ten seconds the idle drops and will either almost stall the engine or occasionally does stall the engine. This happens in drive as well, and when driving, since the rpm's drop and come back up, the vehicle surges at low speeds. The rpm drop only occurs when any A/C component is on (A/C, defroster, or re-circulation), when just the vent is on, the rpm does not drop and the engine run fines.

Please help me with this question, it seems like this is not a one of a kind problem.

Thank you in advance!
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Saturday, January 26th, 2008 AT 8:52 PM

10 Replies

Tiny
PEAR69
  • MEMBER
Sometimes when you disconnect the battery the engine must go through twenty five running cycles to reboot the computer. Or your IAC valve may be failing. Be sure your battery connections are tight and clean.
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Sunday, January 27th, 2008 AT 6:09 AM
Tiny
BRIAN 1
  • MEMBER
Might want to try this.found bulletin #1878920. Engine stalls when air conditioning is turned on at idle - keywords HVAC rough condition CJ2 CJ3 surge. Engine may stall with the air-conditioner on and or while adding additional loads to the engine at idle. An example of an addition load would be turning the steering wheel left or right with the air-conditioning on. This type of stall usually occurs during idle or slow parking lot maneuvers. This concern may not set any diagnostic trouble codes.

Clean the throttle body bore and the throttle valve plate using a clean shop towel with GM top engine cleaner, GM P/N 1052626 (Canadian P/N 993026) or AC-Delco Carburetor Tune-Up Conditioner, P/N X66-P, or an equivalent product.

Here is a guide to help you see what I am talking about:

https://www.2carpros.com/articles/throttle-actuator-service

Please let us know what happens.

Cheers
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Sunday, January 27th, 2008 AT 5:16 PM
Tiny
PEAR69
  • MEMBER
When you turn on the A/C, the A/C compressor kicks in. This puts a small load on the engine. The rpm's should go down a little. However, when you disconnected the battery, all the sensors that compensate for this load- lost power. The IAC valve can very easily cause the problem you describe and may need to be reset. To do this follow the following:
1: disconnect and remove the IAC valve.
2: measure the distance from the tip of the pintle to the mounting flange. It should be 1 and 1/8 of an inch, if not push the pintle in so it is.
3: re-install the valve.
4: cycle the key on for ten seconds and off for ten seconds. This resets the valve.
5: Start the engine (do not press the gas) and let it idle for five minutes, then shut it off for thirty seconds. Then start the engine again and drive around for a while and test the A/C. During all these steps do not turn on the A/C until driving around during step 5. Let me know how you make out.

https://www.2carpros.com/articles/stall-at-idle

and

https://www.2carpros.com/articles/how-to-replace-an-idle-speed-control-motor-iac

By the way: the IAC valve is the idle air control valve. This valve controls the amount of air allowed to bypass the throttle plate when the throttle plate is closed or at an idle position not necessarily at engine idle, it is at throttle position idle.
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Tuesday, January 29th, 2008 AT 1:03 AM
Tiny
JENNCRRT
  • MEMBER
I have a 2004 also and it was doing the exact same thing.

Sure enough, cleaned the throttle body and problem solved! I also read elsewhere that this is caused from not using "top tier" gas. (Ex. Shell, Chevron) I have always used Walmart, or Sam's. I have joined the trailvoy forum! It is a great site. Has anything you would ever want to know about Trailblazers from other owners. Browsed this site before I found it and thought I would share!
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Thursday, February 21st, 2008 AT 3:22 PM
Tiny
DPOTTER
  • MEMBER
Your problem is a dirty throttle body. Had the same same happen after changing the battery. A good friend sells Chevrolet's and asked the service manager to confirm what I found on line. Over time the car's computer adjusts for driving conditions, engine wear and etc, with a dirty throttle body (which is normal) the computer adjusts. When the battery is changed, it resets to factory settings. So the computer thinks you have a brand new vehicle, with a clean throttle body and regulates fuel/air to that. So it stalls when an extra load is applied. A two dollar can of carburetor cleaner and about twenty minutes will fix you right up. I am so sick and tired of people on here spouting off with what they think is the answer. I had no clue until I started looking on line. Twenty years ago would have been out at least $500.00 at the dealer for this. For all its faults, the internet is a God send.
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Tuesday, June 17th, 2008 AT 7:20 PM
Tiny
MSM1462
  • MEMBER
The dirty throttle body is the cause of surging after disconnecting the battery. It makes sense to me since my throttle body has 105,000 miles on it. To help others out, this happen to me when the defroster was on. Keep in mind, defrost mode automatically turns on the AC if it is warm enough out. This made it difficult to find the cause. Would not surge or die in the colder weather. Twenty five degrees is the threshold give or take a little.

Throttle body runs great with a clean throttle body. It was easier to clean by removing it. Four bolts, vacuum hose and a wire connector to remove. It also helps prevent washing the grime into the manifold.

Love the internet!

Happy trailblazing! : )
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Tuesday, January 12th, 2010 AT 10:58 PM
Tiny
GHOSTRIDERMC1
  • MEMBER
I know this post was created a while back but I would like to say it was extremely helpful! When the battery when out and I had to replace it the car would almost stall when the A/C tried to engage. I suspected a compressor but before I contacted anyone I used the old faithful "Google" and found this thread. After multiple unsuccessful cycles I decided to purchase some throttle body cleaner. It took about one hour to take apart/clean and put back together. Low and behold, praise God, the problem immediately disappeared and the car runs like new!
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Saturday, August 14th, 2010 AT 10:11 PM
Tiny
DANNO28
  • MEMBER
I have to agree it was very helpful. I have a 2003 Trailblazer and had to replace the battery. When I went to use the A/C at low speeds the rpm's would drop and the truck would stall. Figured it had to be related to replacing the battery somehow and found these posts. Cleaned my throttle body and problem solved. Better then paying a mechanic to fix it. Thanks a lot guys!
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Saturday, May 28th, 2011 AT 2:12 AM
Tiny
AWFCOUGAR
  • MEMBER
For the most part this response would be correct. However, the 360 platform does not contain an IAC. Cleaning the throttle body is going to be your 99.9% cure all to the problem.
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Thursday, May 8th, 2014 AT 7:24 AM
Tiny
HECTOR1974
  • MEMBER
  • CHEVROLET TRAILBLAZER
Hello and thank for the help.
My car is a 2004 model year and I have 58,422 miles.
I have some type of electric problem, yesterday I smelled
some really bad rotten odor and my dad saw some smoke coming out of the battery.
I purchased a new battery and I installed it. To this point every
thing is normal. I tested the battery and it show 12.6 volts. Then I installed and I tested again and it show 14.4 volts. I tested all the electricity in the car. Then I find this;
every time the I turn the A/C on the acceleration drops to 200 rpm's or less. I tested the alternator again and it goes to 13.5 volts. Then I saw that every time the A/C compressor try to start the rpm goes down and when the compressor stops, the rpm come back to normal.
I know a little mechanic, but this time I am confused in between the alternator and some part of the A/C.
Please help me.

Thank you to all the mechanics who answer this.
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Wednesday, August 23rd, 2017 AT 12:25 PM (Merged)

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