[SOLVED] Trailblazer stalls at idle when defrost or A/C turns on

[04TBStephanie]

Hi, everyone, this is my first time posting on here! Ok I just got an 04 TB with 72,000 miles on it. When we first got it the thermostat went out within a week but it was replaced and good now! Now when I turn my car on and let it sit its just fine, but when i turn the defrost or A/c or just heat on at idle my car dies. Thr RPMs just drop out. So I took it back to the dealership and their mechanic said he cleaned some hose and recalibrated some blades. When I got back in my TB and started it up and turned on the defrost again it still dropped down into the 500's but kicked back up but it is still dropping into the 500's alot. I called a real chevy dealership and they told me that whatever this "mechanic" did sound like BS! I'm thinking its my fan clutch because my husband has an 05 TB with 73000 miles on it and it was doing the same thing and this chevy dealership replaced the fan clutch and now it has no problems what so ever. Both of our TB's started doing the same thing around the 72000 mile marker. Is this typical? What do you guys think??? What do you think the "mechanic" really did???? Any help would be greatly appreciated.

[bvad02]

it is most likely just a dirty throttle body. follow this how to and should clear up your problem.
http://forums.trailvoy.com/articles....ticle&artid=91

[WOOLUF1952]

I think the "mechanic" did nothing. The dirty throttle body is 99.999% the problem. Many forum members clean their t-body every 30k miles. Its is an easy and cheap fix.

[0202-TB]

The throttle body cleaning should be at the top of your list of things todo..... I changed my battery, then it idled fine but when I turned on the AC, RPM would drop to 200 compressor shut off. it would cycle rapidly 2 seconds max. RPM 600--200--600. sometimes would stall. I cleaned the throttle body and it completely fixed it all. I was totally amazed. The best $3.00 I ever spent.
Long story short, DO IT...
Steve

PS, welcome!!

[04TBStephanie]

Thanks so much it absolutely was the throttle body, i made the "mechanic" do it. lol

[yannyfreak]

Hi all, just read this older post trying to troubleshoot my problem and something grabbed my attention. I just replaced the thermostat a couple of days ago so I had the battery disconnected for several hours. Seems like this post is refering to a stalling problem after a thermostat replacement as well. Just a coincidence??? My car ran flawlessly until removing power to do a thermostat job. Could something be glitched in the tuning from a computor reset or something?? My symptoms are the exact same stalling as explained here. Just a thought, any input would be greatly appreciated. (I'm going to clean the TB of course, its due anyway)
Thanks, Jesse

[RayVoy]

Dozens and dozens of threads on stalling problems caused by the dirty throttle body.

Your problem falls under this heading as well......................yes it does.

As the tb gets dirty, the PCM adjusts the fuel mixture to allow the engine to idle smoothly (based upon info provided by the O2 and other sensors).

When you disconnect the battery..... for any reason..... the "adjustments" (discussed above) are erased from the PCM memory; and when the truck is started, the factory tune is in the memory.

The engine now has a dirty tb and a tune for a clean tb, the result is an engine that idles rough and stalls under load.

Give it some time, and it will re-adjust it'self, but the best fix is to clean the tb.

[yannyfreak]

Thanks Ray. That makes perfect sense. Going to clean it right now

[WOOLUF1952]

Just make sure you use a throttle body safe cleaner.

[yannyfreak]

Throttle body cleaned. Problem is gone. Thanks guys!