03, Trailblazer 4.2L, ruff idle in gear or with a/c on.

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carriedi
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Re: 03, Trailblazer 4.2L, ruff idle in gear or with a/c on.

Unread post by carriedi » Tue Jul 07, 2015 11:41 pm

you should hook up to a scanner and see what it going on when it's running badly. There's no check engine light on? What is the engine rpm when it's idling badly with the engine in gear or with the ac on?
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Beaver

Re: 03, Trailblazer 4.2L, ruff idle in gear or with a/c on.

Unread post by Beaver » Tue Jan 09, 2018 8:14 am

Go to advance auto and rent a compression tester .and make sure u have the right compression in every cylinder.it goes in the spark plug hole .make sure it at least 150 psi in every cylinder.if it is your head is good

mjblack37

Re: 03, Trailblazer 4.2L, ruff idle in gear or with a/c on.

Unread post by mjblack37 » Wed Sep 05, 2018 8:00 pm

mrbozo wrote:
> Hello to All: :)
> Ok I have a good one for you mechanic's out their. I have an 2003
> Trailblazer with a 4.2L, it is the XLT body.
> The problem that I an having is that their is a ruff idle:
> 1) When I put the vehicle into gear, driver or reverse their will be a
> slight ruffness to the idle. It is smooth when it is in Park and Nutural.
> 2) Very ruff when the A/C is turn on and idling. When you drive their
> is not problems at all runs like a champ.
> What I have already done so far to the vehicle:
> 1) Replace the Spark Plugs with AC Delco Iridium #41103 and gap them at
> .044
> 2) Clean the throttle body, no change so I replaced it with a new
> ACDelco Throttle Body Assy.
> 3) Replaced the Exhaust Cam Position Actuator Solenoid
> 4) Reset the cam sensor and crank sensors with my scanner,
> "Modus"
> 5) Replaced the MAP Sensor, just because.....
> Now I am still at step one, I still have a ruff idle with my vehicle and I
> have read that it is the Throttle Body and that is 99.9999999% of the
> problem.
> I have read that the coolant sensor could be bad, the O2 sensor is not
> working correctlly and that I could have a weak coil pak.
> Would anyone have a idea of the issue that I am having. I am at the point
> that it could be a motor or trans mount maybe the A/C Compressor it self.
> The vehicle at this time has 94,456 miles, own it from new and I do keep
> up on my maintenance.
> So is their someone that might have a good idea of what the issue maybe.
>
> Thank you for reading this and for any suggestion that you will have. replace both engine mounts use ONLY AC Delco or u will have same problem

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carriedi
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Re: 03, Trailblazer 4.2L, ruff idle in gear or with a/c on.

Unread post by carriedi » Thu Sep 06, 2018 9:29 pm

oh, on the frozen O2 sensor:
I have a dozen or so, O2 sensor wrenches or sockets. there are all sorts of angles and obstacles in the way to get at the O2 sensors. Getting at them is half the battle. If you can get a good grip on the sensor and have room to turn it but it is just froze up solid you may have to use heat to get it out. I have a mini-inductor that uses electric current to get the sensor hot. Red hot without puting heat where it may do damage to other things around the sensor. Sometimes when the sensor comes out it may damage the threads. You may have to re-thread the hole. Heli-coil or put a new bung in the pipe.

you can try some kind or rust penetrating fluid and let it set for at least 20 minutes and see if that helps.
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carriedi
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Re: 03, Trailblazer 4.2L, ruff idle in gear or with a/c on.

Unread post by carriedi » Thu Sep 06, 2018 9:35 pm

this vehicle should have a misfire counter that could pick up misfires that may not set a code yet. Graphing the cylinders you can see if certain cylinders are missing on the rough idles and concentrate on those cylinders. Move coils, spark plugs, injectors, check your crank pulley, make sure it's on tight. Rather than just putting parts on to see if that does it, take it to a shop that can diagnose something and then see if you can fix it. At least now you would have something to back up putting parts on.
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carriedi
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Re: 03, Trailblazer 4.2L, ruff idle in gear or with a/c on.

Unread post by carriedi » Thu Sep 13, 2018 7:17 pm

something that could affect your idle too is having a problem with your AC. Make sure your ac compressor and clutch are working okay. I had a truck that came in with the ac clutch that was broken. It was way off balance but it still turned on. It vibrated like crazy as you speed up.
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