2003 Trailblazer Idle drops when AC or Rear Defrost is on

[pdesimone48]

I have a 2003 Trailblazer with 90,000 miles or so. Recently, I've noticed when I put the AC on, or the heat and one of the 2 defrost settings on the dial on the heater switch my idle drops, flucuates and then stalls the vehicle. Also, without any heat or AC on and I turn on the Rear Defrost button, it does the same thing. The volt gaugestays steady at 14 volts. So, it seems whenever I have a heavy draw on the system my idle drops and the truck stalls out at low RPMs. when I'm on the highway, I can put these devices on (I feel a drag on the system, but the higher RPMs seem to compensate). It only happens at low speeds or at idle. Any suggestions would be appreciated. Phil

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[rbarrios]

most likely-----

sounds like you recently disconnected the battery- and your throttle body is very dirty....
when you do this, the computer forgets parameters that it has learned over time.
so when you run the car again- it runs OK.....but turn on the AC, or recirculate air button (both turn on the compressor), you get this idle fluctuations that go up and down and at times will kill your engine. (at idle, or slow driving and making a turn, or on highway it wont shut off, but you can feel the drag).
the fix is simple.......
get throttle body cleaner ($5)
disconnect battery (for at least 30 min).
clean the throttle body.
reconnect.
should be fixed.
for instructions on how to.......
checkout www.trailvoy.com
theres pics and directions over there/

[pdesimone48]

Thanks for the info.
I'll give it a shot and let you know how I make out.

[pdesimone48]

I just want to say thanks to rbarrios. I got a can of Throttle Body Cleaner for $2 and shot the whole can in it a little at a time and it solved the problem. At first it ran a little rough and if I revved the engine and then let it come back down to an idle it jumped around a little and then stalled out but if I just let it idle it ran OK (this is with the AC on). Maybe I should have disconnected the battery like you suggested but I didn't want to lose all the presets on my radio. Anyway, this morning I drove it to work about 25 miles and it seems to have straightened itself out.

Now I have to check for a vaccum leak. After I shut my engine off, I heard a hissing that sounds like it could be a vaccum leak or something. Any suggestions?
Anyway, thanks again. It's nice to get advice that actually works.

Phil

[rbarrios]

recommend you disconnect the battery for 30 min.
this will get your throttle body/idle to work much better.
the hissing is probably the the AC condenser- after use it makes these noises.
since you were operating the AC- thats what I think it may be.

[rbarrios]

some of the guys over at www.trailvoy.comwill remove the throttle body completely and give it a good cleaning.
they find that it is very dirty.
in the 124,000 miles on my trailblaxer, I have only disconnected the battery(30 min) and then I spray throttle body cleaner into the throttle body and move the door back and forth to help dislodge crud that has accumulated.
after 30 min I restart (it runs rought for a little while it burns off the cleaner) but after that it purrs......
I do this maybe once a year.
Just be very careful not to move the flap on the throttle body while the car is running or key in the ignition... it may end up costing you $$$ to buy a new throttle body..