NEED HELP Rough idle 06 trailblazer 4.2

[Garydoolin]

Hey guys. I have a 2006 trailblazer 4.2 164000 miles. I have had the rough idle in it since I had it. I have pulled and cleaned the TB several times over the years I've had it (I bought it when it had 80000) and it would always fixed It. I would always do the relearn procedure also. It started again about 2 months ago. It idles rough in park, neutral, any way you slice it. The tach moves from 600 down to about 300 and back and forth. It is worse when the A/C is on but it is there regardless. It runs fine while driving. I took the TB off and it was not dirty at all this time. I just put new plugs in it ac delco 41-103. No change. We hooked it to the scanner and I have the following codes.

PO014 exhaust cam position system performance

PO017 CKP TO exhaust Cmp correlation B1

PO420 catalyst efficiency low bank 1
( I cut the cat off. Gonna do a tune to delete it and fix this problem)

PO455 evap leak large
(Gonna change the vent valve canister as it showed a leak on smoke test)

PO463 fuel level sensor.
(Replacing fuel pump with new sending unit)

Also it is lacking power and I'm getting bad MPG. 12 at best. I was getting 15-17 when I first got it. I appreciate any info on this. Thanks.

Gary

 

[Garydoolin]

Hey guys. I have a 2006 trailblazer 4.2 164000 miles. I have had the rough idle in it since I had it. I have pulled and cleaned the TB several times over the years I've had it (I bought it when it had 80000) and it would always fixed It. I would always do the relearn procedure also. It started again about 2 months ago. It idles rough in park, neutral, any way you slice it. The tach moves from 600 down to about 300 and back and forth. It is worse when the A/C is on but it is there regardless. It runs fine while driving. I took the TB off and it was not dirty at all this time. I just put new plugs in it ac delco 41-103. No change. We hooked it to the scanner and I have the following codes.

PO014 exhaust cam position system performance

PO017 CKP TO exhaust Cmp correlation B1

PO420 catalyst efficiency low bank 1
( I cut the cat off. Gonna do a tune to delete it and fix this problem)

PO455 evap leak large
(Gonna change the vent valve canister as it showed a leak on smoke test)

PO463 fuel level sensor.
(Replacing fuel pump with new sending unit)

Also it is lacking power and I'm getting bad MPG. 12 at best. I was getting 15-17 when I first got it. I appreciate any info on this. Thanks.

Gary

Additional info it it helps it seems like it does it after it warms up to operating temperature.

 

[mrrsm]

Welcome to GMT Nation...

Your BEST Point Of Origin for MOST Engine Q&As begins and ends with @Mooseman 's Epic FAQ Thread:

FAQ: Vortec 4.2L I-6

This sticky is for links to the most asked about questions, info, specs and general knowledge of the Vortec 4.2L I-6. If you see a thread that should be considered to be added here, click on the button with a note indicating that it should be added. General Vortec 4200 Wiki (external site)...

gmtnation.com

 

[TollKeeper]

It almost sounds like the VVT solenoid, if not the... the... I cant remember what its called. Its on the cam sprocket and forwards or retards the timing on that cam..

Anyways, the 4.2 is very sensitive to oil, and the cleanliness of the oil. When the VVT Solenoid gets even a tiny bit dirty on the screen, you can get the problems you list.

I am no expert on the 4.2, so I will let the experts explain it further.

A recent video put up on YouTube about the P0014 on a 2006 Trailblazer, and how to replace it.

 

[Mooseman]

Try the CPAS first as explained by @TollKeeper and also clean the cam position sensor. If that doesn't resolve it, try having a CASE relearn done, which requires an advanced scanner or Tech 2.

It could also be the cam phaser (aka: adjustable exhaust cam sprocket). That's a bit more involved to replace.

 

[TollKeeper]

CAM PHASER!!! Thats the word(s) I was looking for!

 

[TollKeeper]

Cam Position Sensor video for you...

 

[Garydoolin]

Thank you both. I will try these and report back.

 

[Garydoolin]

OK I change fuel pump and that fixed the po463. Fixed the evap leak. Did the tune to delete the cat and back o2 sensor. I checked the oil when I read that it could cause the po014 and po017 codes. Sure enough it was low. Close to 2 quarts. Changed the oil and don't have those codes any longer.

Now as we were doing the tune and it was hooked to the laptop we were looking at live data and the rpms was bouncing between 590 and down to 420. Back and forth. Still wose when A/C was on but still there without it on. I have cleaned the TB as stated above and still no help. Also did the relearn. What else could it be? Do you think my TB is bad?
Thanks
Gary

 

[Mooseman]

What relearn did you do? Our usual way is to disconnect the battery or pull the PCM fuse 10 for at least 30 minutes while we clean the throttle body.

 

[Garydoolin]

What relearn did you do? Our usual way is to disconnect the battery or pull the PCM fuse 10 for at least 30 minutes while we clean the throttle body.

It is idling good now. I cleaned the TB again and I had the battery disconnected. After I got it cleaned and the battery hooked back up I did this, starting with number 2

 

[Mooseman]

That may work for V8's but it certainly doesn't for the 4.2. The battery disconnection is the only one that works for sure. Glad you got it figured out.

 

[budwich]

I do believe that's the process outlined by the OP that's in the GM SI when no tech 2 is used.

 

[Garydoolin]

That may work for V8's but it certainly doesn't for the 4.2. The battery disconnection is the only one that works for sure. Glad you got it figured out.

I didn't know that. I guess it was the battery disconnection is what did it. Either way I'm just glad it is fixed. Thanks for your help.