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2006 chevy trailblazer_ls
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Discussion Starter #1
Looking for a little assistance here. My Trailblazer seems to run fine once I am moving but the idle is very rough. I have done a lot of reading and so far have cleaned the throttle body and still have a very rough idle. I purchased a fuel filter but can't seem to locate the filter, picture would be awesome. Can someone fill me in and also if you have other suggestions as to how to fix my issue?
 

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2004 gmc
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26,181 Posts
Just confirming you disconnected the battery during the cleaning?

Filter's just forward of the fuel tank.

How many miles, and when did you last change the oil, plugs and air filter? Plug wells can collect oil and/or water and ruin the idle. Old oil can clog screens on the cam position actuator/solenoid.

Next things to search for are the camshaft position sensor and cam position actuator.
 

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2006 chevy trailblazer_ls
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Discussion Starter #3
Just confirming you disconnected the battery during the cleaning?
Yes I followed the guide here on trailvoy.com

Filter's just forward of the fuel tank.
Thanks!

How many miles, and when did you last change the oil, plugs and air filter? Plug wells can collect oil and/or water and ruin the idle. Old oil can clog screens on the cam position actuator/solenoid.
81,000 miles. It is currently time for an oil change, light just started coming on or its been roughly 5,000 miles but the oil still looks decently clean so I don't think that is the issue. As for the plugs I have note replaced them yet and have had this vehicle for about 40,000 miles so I assume they have never been replaced. Probably about time, first I am going to tackle the fuel filter, hopefully not to difficult, timely or messy. I hate getting fuel all over the place. While I am at it I will change the oil too.

Next things to search for are the camshaft position sensor and cam position actuator.
I will post back if that doesn't fix the issue as I am unsure of where the camshaft position sensor and cam position actuator are or what do do if it comes to that. Thanks for the tips.
 

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2006 chevy trailblazer_ls
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Discussion Starter #4
Got the new fuel filter in and it made no difference, I still have a rough idle and it runs fine while operating/driving but run rough at stop lights etc. By the way this is an issue that just suddenly started to occur and wasn't something that slowly got worse. Any other pointers?
 

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2002 chevy trailblazer_ltz
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When you say it runs rough, do the RPM's drop to almost stalling and pick up again? If it does, you may need a new forward O2 sensor.

Matt
 

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2002 chevy trailblazer_ltz
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A bad O2 sensor could be messing with you A/F ratio causing a rough idle, but I would check spark plugs and coils first. I just had to replace the spark plugs at 75K because the SES light came on and the engine was misfiring. Sure enough #1 was fouled. Since the weather got cold it had been a little louder at idle and the mpg went down some, but i just thought it was due to the cold. Now it has the new plugs and you can't even tell its running, just like when it was new.

Good luck.
 

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2004 chevy trailblazer_ls_ext
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Rough Idle

Having the same issue on my 04 TB. Replaced plugs with AC Delco, cleaned throttle body (left batttery cables off for more thatn 30 min). Still no luck.

Where are the cam position sensor or cam position actuator/solenoid?


Tony
 

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2003 chevy trailblazer_ltz
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167 Posts
well mine drops down to 600 rpm and stays there and i just replaced the plugs and cleaned the tb. the af is about a year old but still looks new and the fuel filter was changed about 15 thow ago which i only change every 30.
 

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2002 chevy trailblazer_ltz
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Got the new fuel filter in and it made no difference, I still have a rough idle and it runs fine while operating/driving but run rough at stop lights etc. By the way this is an issue that just suddenly started to occur and wasn't something that slowly got worse. Any other pointers?
A coil pack that is starting to get weak will cause a miss at low RPM. Unfortunately, unless it throws a SES code, it will be hard to find out which one it is. :undecided
 

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2002 chevy trailblazer_lt
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Clarification

Is it a rough idle or a vibration? Does it only occur in drive while stopped? Does the rough idle go away when you put the car in park or reverse? If so, it could be motor mounts. Look for the post from Roadie on them.
 

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2002 chevy trailblazer_ltz
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Rough Idle too

I have been chasing it too. I have replaced the motor mounts with original GM mounts, changed plugs and cleaned the throttle body. It is not horrible but it seems to be somewhat intermittant. I lean towards it being the Camshaft Acutuator Solenoid. It could be a coil pack or a wire running to it or maybe even the fan clutch. I do notice that my temp will stay right at 210 and once in a while I notice it drop down a couple of tick marks and then shoot right back up.

Any insight or ideas would help.
 

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2003 chevy trailblazer_ltz
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ruff as in 600rpm in all gears. trust me and its not a viberation at 600 rpm. its not a coil pack either cus i had them cheched out today at chevy dealer and thay r dumb any way
 

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2002 chevy trailblazer_ltz
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Rough Idle

The more I think about it, I am leaning towards trying the disconnect the battery, remove and clean the Throttle Body and then also take off the CPAS and check it/clean it to make sure it is not fouled, after that I will probably move to the fan clutch. After that I will just live with it. It is not a horrible thing just something I notice and that makes it enough of an issue to me. I doubt it would be a cylinder sleeve issue as that would be consistent and get worse.

Then I may also do the PCM Tune after I get a little more time.
 

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2003 gmc envoy_slt
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Vibration at Idle

My 2003 GMC Envoy idles at 6000 RPM and vibrates the grill. This happens in either park or at all stops. Once I accelarate the problem goes away.

I replaced the plugs, the air filter, and cleaned the throttle body with the battery unplugged for 50 minutes.

This occurs with or without the A/C running.

Any other thoughts would be appreciated?
 

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2002 chevy trailblazer_ltz
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If you have the 4.2 I6, I would recommend 2 things. 1st, replace the Camshaft Position Solenoid, from either parts4chevy or rock auto it is priced very good (get the AC Delco one) and either go to the dealership and get a pcm update for around $100 or doing the PCM update/exchange for around $250-300. I did the dealership route and there were approx 14 updates and 2/3 of them related to the idle issue and vibration. the others were for odd shifting going into and out of 1st gear.
 

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2003 gmc envoy_slt
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Low Idle and Vibration

Thanks for the response!

Also - just for clarification purposes - I mean 600 RPM's idling - not 6,000 - if it were 6,000 at idle - I would be more concerned!

I will go to a GMC dealership and have the PCM updated. GREAT IDEA. I bought the vehicle used and don't know the past history but I did put 50,000 miles on in a year - and NO REGRETS!

These vehicles are built for a very long life performance. I drive a considerable amount and usually go 200,000 to 300,000 miles - I believe this is a 300,000 mile vehicle.

The rough idling hasn't always been there. Tried to use Techron to see if it was fuel injector related - no luck........ So far - Techron - replaced plugs, Cleaned throttle body - replace air filter...... On top of that just replaced water pump and fan clutch - now the clicking is gone! Tensioners probably need replaced because it sounds like an airplane when I first take off!

Thanks for all the help and advice - what an awesome forum!
 

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2003 gmc envoy_slt
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Problem Solved

After cleaning throttle body, replacing spark plugs, and so on and so on - I found the vibration. :bonk: The engine mounts needed replaced!

I purchased them at GMPartsdirect.com and had a mechanic install them for $200.00

My vehicle is smooth and when I shut it off - It no longer kicks like a mule!

Mechanic told me engine mounts going bad on these vehicles is very common.
 

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2005 isuzu ascender
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13 Posts
SO what happens if......

I cleaned the throttle body about a 3 months ago.....I didn't unhook the battery....... sorry I hadn't read the "how to" here. THe vehicle ran fine for 2 months, then out of the blue it starts idling horrible....in gear or neutral or park....shakes so bad it about makes me sea sick....radio antenna vibrates around like one of the hula girls on the dash of old cars.
Could not unhooking the battery have caused this?
No codes seem to be thrown no idiot lights on, however my fuel mileage seems to have dropped to 14 mpg HIGHWAY!!!!!!

ANy help would be drastically appreciated.
 
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