Rough idle

Tiny
NYTEMARE68
  • MEMBER
  • 2005 CHEVROLET TRAILBLAZER
  • 4.2L
  • 6 CYL
  • 4WD
  • AUTOMATIC
  • 156,000 MILES
Starts fine but when I start to drive as long as I am on the gas it runs fine. When I come to a stop the vehicle idles down and rough, bad enough that at times it stalls or goes into limp mode. I have tried multiple things to no avail, out of work right now so need possible cheap fix. Cruise control not working as well. Please help!
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Saturday, October 17th, 2015 AT 11:14 AM

42 Replies

Tiny
HMAC300
  • MECHANIC
  • 48,601 POSTS
Try cleaning throttle plate on both sides disconnect the battery first. Here is a guide to help:

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

Please run down this guide and report back.

Cheers
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Saturday, October 17th, 2015 AT 1:30 PM
Tiny
NYTEMARE68
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Thanks! Worked perfect for my car. I love this site.
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Sunday, October 18th, 2015 AT 10:18 AM
Tiny
DD142
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  • 1 POST
  • 2005 CHEVROLET TRAILBLAZER
Six cylinder two wheel drive 92,000 miles.

Recently the check engine light came on. I took the vehicle to the shop and they said they needed to change the fan clutch and gas sensor sending unit for the gas pedal. When the light was on, the engine was running rough when in drive. Once I received the vehicle back, the check engine light was off but the rough idle was still there. I took it back to the garage and now they are saying that the water pump needs to be replaced due to the bearing being bad. The water pump is not leaking at all.
My question is, can a worn water pump cause rough idling? They said they checked the engine on the computer and the engine is not missing. Help!
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Thursday, August 2nd, 2018 AT 7:01 PM (Merged)
Tiny
JACOBANDNICKOLAS
  • MECHANIC
  • 108,014 POSTS
The water pump cannot cause an engine miss. Have you checked for vacuum leaks?

This guide will help us.

https://www.2carpros.com/articles/engine-misfires-or-runs-rough

Please run down this guide and report back.

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Thursday, August 2nd, 2018 AT 7:01 PM (Merged)
Tiny
KBFOUR
  • MEMBER
  • 1 POST
  • 2005 CHEVROLET TRAILBLAZER
  • 6 CYL
  • 2WD
  • AUTOMATIC
  • 111,000 MILES
Engine idle is somewhat rough. Ehen A/C is turned on the engine will shut off. Replaced coil and plug on cylinder six based off misfire code.
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Thursday, August 2nd, 2018 AT 7:01 PM (Merged)
Tiny
RASMATAZ
  • MECHANIC
  • 75,992 POSTS
Try cleaning out the idle air control valve and test the throttle position sensor and manifold absolute pressure sensors.
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Thursday, August 2nd, 2018 AT 7:01 PM (Merged)
Tiny
PIERCE1001
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  • 1 POST
  • 2005 CHEVROLET TRAILBLAZER
  • 6 CYL
  • 4WD
  • AUTOMATIC
  • 45,000 MILES
My vehicle has an issue with the idle and taking off. At times the idle will be at 900 which I have been told is normal. While idling at this rpm everything is fine. At other times it will drop down to 600 and wants to stall. When you give it gas it bogs down and tends to stall. Also, when the idle is this low it also hesitates on take offs. I am also getting a lean engine code. I have changed the intake gasket, cleaned the throttle body, changed the O2 sensor, MAP sensor, cleaned mass air flow sensor and also added fuel injector cleaner to my fuel. Would the secondary air intake cause this problem or is there anything else I can check?
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Thursday, August 2nd, 2018 AT 7:01 PM (Merged)
Tiny
LEGITIMATE007
  • MECHANIC
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Possibly, but at this point I do not think that is your problem. Check your idle air control valve for faultiness.
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Thursday, August 2nd, 2018 AT 7:01 PM (Merged)
Tiny
TIKI
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  • 1 POST
I have the same problem with my 2005 Trailblazer. Is the Idle Air Control Valve the problem? Could it be the coil(I was told it is a common problem) or even the fuel filter?
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Thursday, August 2nd, 2018 AT 7:01 PM (Merged)
Tiny
KYLE HODGES
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  • 1 POST
  • 2005 CHEVROLET TRAILBLAZER
  • 6 CYL
  • 2WD
  • AUTOMATIC
  • 110,000 MILES
When A/C is on idle is below 1,000 rpm and stumbles like it is going to stall out. Does this year have an idle air control and could that be the problem?
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Thursday, August 2nd, 2018 AT 7:01 PM (Merged)
Tiny
RAZERBACK
  • MEMBER
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Check for any vacuum leaks first. Then check air filter. It sounds more like it is having a hard time keeping up. I do not think it is any switches. When was the last time you did a tune up? Any check engine lights come on?
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Thursday, August 2nd, 2018 AT 7:01 PM (Merged)
Tiny
CHEVYBOI42
  • MEMBER
  • 1 POST
  • 2005 CHEVROLET TRAILBLAZER
  • 6 CYL
  • 2WD
  • AUTOMATIC
  • 144,628 MILES
My vehicle is idling rough. I did a tune up and even had my fuel system cleaned with the three step process at Tires Plus. It is still doing the same thing. Yes my engine light comes on for a day and goes off for a few days and then comes back on and goes off in the same manner. I was told that my catalytic converter is bad. I had an after market catalytic converter put on at the beginning of the year though. And as I was driving last night my lights began flickering and my battery needle was moving up and down every time the lights flicked. What could the problem be? I have done a lot of traveling and I have 144,000 miles on my vehicle. This did not start until about three trips to Texas and back from Georgia.
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Thursday, August 2nd, 2018 AT 7:01 PM (Merged)
Tiny
RASMATAZ
  • MECHANIC
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First step here is have the computer scanned for code/s, you have a problem within the engine management system that caused the CEL to turn on. This is your starting point of diagnosis, finding out what is going on.
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Thursday, August 2nd, 2018 AT 7:01 PM (Merged)
Tiny
MAHOY78SPYDER
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  • 2 POSTS
  • 2004 CHEVROLET TRAILBLAZER
  • 6 CYL
  • 4WD
  • AUTOMATIC
  • 88,684 MILES
Hello, I have the EXT model. No work done to motor other than oil changes. Engine idles very rough when cold, even stalls occasionally, but after a couple minutes of driving (when warmed up) it runs just fine. Is this a sensor problem, and if so, which?


https://www.2carpros.com/forum/automotive_pictures/400662_114_2.jpg

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Thursday, August 2nd, 2018 AT 7:01 PM (Merged)
Tiny
RASMATAZ
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Test the resistances on the coolant temperature sensor hot and cold. Also clean out the idle air control valve.

GM Coolant temperature sensor

Temp Resistances

-40 100.7
40 7.5
100 1.8
210 185
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Thursday, August 2nd, 2018 AT 7:01 PM (Merged)
Tiny
MAHOY78SPYDER
  • MEMBER
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Thanks for your blazingly quick response. I did a check on the IAC and learned that 2004 is the first year Chevrolet assembled it with the entire throttle body so it is no longer a separate component. I can see it visually on top there but don't see a way to clean it. Any suggestions?

Also, on the coolant temperature sensor. Where is it located exactly?
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Thursday, August 2nd, 2018 AT 7:02 PM (Merged)
Tiny
RASMATAZ
  • MECHANIC
  • 75,992 POSTS
The coolant temperature sensor is located on left front of engine block near the alternator/generator as for the IACV you have to remove it form the TB and clean out. Does yours looks like this?


https://www.2carpros.com/forum/automotive_pictures/12900_IACV_2.jpg

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Thursday, August 2nd, 2018 AT 7:02 PM (Merged)
Tiny
ALEX HOLLAND
  • MEMBER
  • 1 POST
  • 2004 CHEVROLET TRAILBLAZER
  • 4.2L
  • V6
  • RWD
  • AUTOMATIC
  • 183,000 MILES
It has a rough idle when I start it and leave running for a minute. When I drive about fifty mph it acts like it is losing power. Not sure what is wrong.
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Thursday, August 2nd, 2018 AT 7:02 PM (Merged)
Tiny
KEN L
  • MASTER CERTIFIED MECHANIC
  • 42,554 POSTS
Hey ALEX,

It sounds like you have a catalytic converter that is partially plugged. Have you replaced the spark plugs recently or the fuel filter?

Here is a couple guides you can use for testing:

https://www.2carpros.com/articles/how-to-change-a-fuel-filter

and

https://www.2carpros.com/articles/how-to-test-a-catalytic-converter

and

https://www.2carpros.com/articles/engine-has-low-power-output

and

https://www.2carpros.com/articles/how-to-change-spark-plugs

Please let us know happens so it will help others.

Best, Ken

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Thursday, August 2nd, 2018 AT 7:02 PM (Merged)
Tiny
TIMSTEPHENS
  • MEMBER
  • 1 POST
  • 2004 CHEVROLET TRAILBLAZER
  • 112,000 MILES
I changed the plugs and fuel filter with no change. I took to AutoZone they hooked up diagnostic machine and it said mass air sensor was bad, but my vehicle is not equipped with a mass air sensor. What should I try next it idles rough and has no power when you push on gas.
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Thursday, August 2nd, 2018 AT 7:02 PM (Merged)

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