2003 Chevrolet Trailblazer Idle

Tiny
GRIM216618
  • MEMBER
  • 2003 CHEVROLET TRAILBLAZER
  • 4.2L
  • 6 CYL
  • 2WD
  • AUTOMATIC
  • 135,000 MILES
When my vehicle is idling it runs fine. If I turn on the defrost the engine bogs down, and almost dies. The engine drops to about 2000 rpm (normally idles around 5000) and the power drops from just above 14 down to almost 9. I thought maybe the a/c compressor kicking on was putting too much strain on the alternator. I replaced the alternator, and it is still doing it. I had someone tell me that it could also be the thermostat or the engine coolant sensor that is not working properly. I also recently had to replace 2 of the ignition coils. Not sure that they would have anything to do with it or not. I found a sensor just above the thermostat housing that had fluid in the plug that I think was coolant. I could not get the sensor out. I am not sure what the sensor is for. Any help would be appreciated.
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Monday, March 23rd, 2015 AT 5:16 PM

9 Replies

Tiny
CJ MEDEVAC
  • EXPERT
IN THESE NEW FANGLED VEHICLES

ANY HEAT MODE W/ "DEFROST"

TURNS ON THE A/C CLUTCH, WHICH IN TURN MAKES THE COMPRESSOR TURN, AND IN THE END, THE EVAPORATOR TAKES MOISTURE OF OF THE AIR BEFORE IT BLOWS ONTO THE WINDSHIELD

HERE'S MAYBE THE SAD PART OF MY HYPOTHESIS

YOUR A/C CLUTCH IS PROBABLY SPINNING FINE WHEN IT'S "OFF" / JUST FREE WHEELIN' AWAY!

IF YOU TURN ON THE A/C OR A DEFROST MODE AND THE A/C CLUTCH ENGAGES THE ACTUAL COMPRESSOR

YOUR COMPRESSOR MAY BE LOCKED UP :-(

IT CANNOT TURN

THIS BOGS DOWN THE A/C CLUTCH, AS IT IS SORTA NOW LOCKED TO THE NON-SPINNING COMPRESSOR. BASICALLY THAT ONE PULLEY CANNOT TURN WITH THE BELTS MOTION

THIS BOGS THE ENGINE DOWN

YOU AND A PAL MOVE THE BUTTONS AND WATCH THE COMPRESSOR

AM I STILL THE BEARER OF BAD NEWS OR AM I WRONG?

YOUR TURN

THE MEDIC
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Monday, March 23rd, 2015 AT 7:13 PM
Tiny
GRIM216618
  • MEMBER
I have checked the ac compressor to see if it spins, and it does still spin when engaged. The heat and ac both work properly. It just bogs the engine down.
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Monday, March 23rd, 2015 AT 8:13 PM
Tiny
CJ MEDEVAC
  • EXPERT
COULD YOU VERIFY THAT IDLE IS AT 2000 AND 5000 AS YOU SAID ABOVE

OR DID YOU MEAN 200 AND 500?

THE MEDIC
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Tuesday, March 24th, 2015 AT 2:13 PM
Tiny
GRIM216618
  • MEMBER
Yes I am sorry. It is 200 and 500.
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Tuesday, March 24th, 2015 AT 2:36 PM
Tiny
HMAC300
  • EXPERT
I've been asked to help out, check battery for condition including load test. Most places do for free. Then replace belt and tensioner as 60k is recommended the tensioner loses tension, belt slips and causes everything to draw down. Make sure the battery terminals are clean as well. Finally clean throttle plate on both sides and iac hole with choke cleaner. The sensor you are talking about kinda behind the alternator is the coolant temp sensor.
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Tuesday, March 24th, 2015 AT 3:06 PM
Tiny
GRIM216618
  • MEMBER
The battery is new. I replaced it less than a month ago. How do I clean the throttle plate and iac hole?
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Tuesday, March 24th, 2015 AT 7:37 PM
Tiny
HMAC300
  • EXPERT
Use choke cleaner and clean both sides of plat e an iac hole there is a article on our repair site here. YOu don't need to remove it to clean it like the article shows.
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Wednesday, March 25th, 2015 AT 7:03 AM
Tiny
GRIM216618
  • MEMBER
I cleaned the throttle body like you suggested. It fixed the issue of the engine bogging down when the ac compressor turns on. However, now when the car is in park the idle runs about 600. As soon as it is put in gear it jumps to about 1500. If you take your foot off the brake it will run about 25 mph without even touching the gas.
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Monday, March 30th, 2015 AT 8:16 PM
Tiny
HMAC300
  • EXPERT
Check for a vacuum leak or the duct work not installed correctly it may have an air leak causeing it then have a pro look at it as I'm currently out of ideas. And have no further suggestions.
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Tuesday, March 31st, 2015 AT 5:55 AM

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