Mysterious Smoke At Cold Start Up!? - Chevy TrailBlazer, TrailBlazer SS and GMC Envoy Forum

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Go Back   Chevy TrailBlazer, TrailBlazer SS and GMC Envoy Forum > 2002 - 2009 TrailBlazer/Envoy Tech > 02-09 Vortec 5.3L V8 Engine and Drivetrain > OEM Issues

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Old 01-29-2011, 08:56 AM
AngryItalian AngryItalian is offline
Junior Member
2007 GMC Envoy Denali
Liquid Silver Metallic 5.3L V8 2WD
Join Date: Jan 2011
Location: Macon, GA
Posts: 2
Mysterious Smoke At Cold Start Up!?

Hello all,

Glad to be finally registered and set up! We bought a beautiful '07 Denali a few months back, and we absolutely love the truck. Not too long ago, I began noticing a fair amount of a blue-ish gray smoke coming from the tailpipe at cold startups. The frustrating thing was it was only an intermittent thing. It was kind of line a vintage airplane that when started, would puff out a large cloud of smoke and then that was it, nothing else. I also noticed the oil level was way below the lower x on the dipstick. The engine has been running fine, no noises, no CEL, etc. I did some early research here, and it seems others have had similar issues with the 5.3 liter. It was almost due for an oil change, so I took it into the dealer to have them check it out.

Their diagnosis was a faulty PCV valve, which they replaced under the 12 mo. Certified B2B warranty. They also recommended (and I took the bait hook line & sinker) to have a throttle body injection cleaning service and some upper engine induction chemical cleaning service done while they were in there. Total bill w/ the oil change was about $240 and all is now well. I will be keeping a very close eye to see if the smoke issue comes back, as well as the oil consumption level going forward. I can get past the oil consumption if that is truly "normal" for this type of engine, but a modern well maintained engine with 60k miles should not be spewing more smoke than the local bingo hall on a Friday night!

Any thoughts or feedback? I am hoping the PCV valve was truly the culprit! Thanks for any comments or help. AI
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Old 03-06-2011, 08:59 PM
Brian P's Avatar
Brian P Brian P is offline
Junior Member
2008 Chevy TrailBlazer LT
Graystone Metallic 5.3L V8 4X4
Join Date: Jul 2009
Location: Long Island, NY
Posts: 59
I caught mine doing this once in a rare while. It would just puff for a second after a cold start. It seems more likely that maybe one valve seal is leaking oil when the engine is stopped in a certain position (IE: the seal leaks when its valve is held open). The 4.8L on my father's truck will occasionally do this as well.

Have you noticed any smoke since the PCV change? At least with my experience I can't imagine it being the PCV since the smoke puff occurs instantly upon startup, as if the oil is already in the combustion chamber. I'll make a note to check my PCV anyway and replace it when I perform the tuneup.

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2008 Chevy Trailblazer LT 5.3
1995 Olds Cutlass Supreme SL coupe 3400 V6
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Old 03-06-2011, 10:14 PM
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bromanjr bromanjr is offline
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2004 GMC Envoy SLT XUV
Indigo Blue Metallic 5.3L V8 2WD
Join Date: Sep 2010
Location: Howell, MI
Posts: 691
I had a related issue with my 5.3 after I purchased it, mostly the oil consumption problem. I never noticed any start-up smoke (but never looked for it either).

When I purchased the truck it had 164,000 miles and an unknown service history. It used oil excessively, about 1 qt/1000 miles with no apparent leaks. After a couple oil changes and many added quarts between changes, I searched for an explanation.

I found that in the TrailVoys, the 5.3, which is an Aluminum block, seemed to have a much worse than normal oil usage history. It seemed the iron block versions in the Pickups/Suburbans/Avalanches were not reporting the same level of the problem. Not sure that the aluminum block was the issue, I kept searching. I found that the PCV chamber inside the Driver side valve cover was faulted for sludging up easily and GM was replacing the Valve cover as a fix for the problem, a TSB (don't remember the number) is what I found.

I found and purchased a new GM valve cover w/new PCV for the drivers side. Put it on and have been seeing vastly decreased oil usage for the last 6,000 miles. Also, on top of this I have been driving aggressively (my normal routine) and as time goes by, it has also been idling and running smoother. I attribute the aggressive driving is helping clean the combustion chambers and rings. So after two 3,500 mile trips and needed maintenance my oil usage is down significantly. Last oil change at 4,000 miles and oil was barely low.

I am hoping for continued normal oil consumption. I thought about just replacing the PCV valve and agree it should help. I chose to replace the valve cover because my engine was extremely sludged (remember, unknown maintenance history) and according to the TSB the cover could not be effectively cleaned plus the PCV chamber had a probable seal failure that was mentioned in the TSB.

182,000 and counting. Superchips 2914 Tune, NAV upgrade.
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Old 03-07-2011, 07:30 PM
AngryItalian AngryItalian is offline
Junior Member
2007 GMC Envoy Denali
Liquid Silver Metallic 5.3L V8 2WD
Join Date: Jan 2011
Location: Macon, GA
Posts: 2
I have not noticed the smoke since we had the PCV valve changed and the oil service/regular maintenance. I am watching it closely though. My wife thinks I'm a nut job (maybe she's right??) since every time we go somewhere together and the truck is cold, as soon as I twist the key I run to the rear to look for the smoke. We've only put a few hundred miles on it since the service, so I can't comment yet on how much oil is being consumed. We're probably heading down to Florida next weekend and will pull my 17' boat w/ us. By the time we get back I will check the oil level to see where things stand. Stay tuned...
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Old 03-07-2011, 08:59 PM
Flying Monkey's Avatar
Flying Monkey Flying Monkey is offline
2004 Chevy TrailBlazer LS
Dark Gray Metallic 4.2L I6 4X4
Join Date: Nov 2010
Location: Ringgold, GA
Posts: 256
usually its the sign of a worn valve guide but sometimes worn rings
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Old 03-07-2011, 10:19 PM
atv hauler atv hauler is offline
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2006 Chevy TrailBlazer LT
Silverstone Metallic 5.3L V8 4X4
Join Date: Feb 2008
Location: Palmerston, ON
Posts: 81
I would lean towards leaky valve seals.
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Old 04-11-2012, 11:00 PM
Willie-TB Willie-TB is offline
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2005 Chevy TrailBlazer LT EXT
Silverstone Metallic 5.3L V8 4X4
Join Date: Apr 2012
Location: Minnesota
Posts: 1
Hi All,

New member & first post - glad to be here!

Anyone know the TSB number of the PCV/Valve Cover fix mentioned in this thread?

My '05 TB with the 5.3 is doing the same thing @ 164K Miles. Runs good & still strong but is now drinking oil 1,000 miles after I had to replace a dead lifter on the other side ($1300!).

Not sure I want to do valve seals first or wish I would have done them when they had the motor apart before.

Is there a reliable way to diagnose worn valve seals?

Comments welcome - in the mean time I'm going to look around more on this site & chevy's for more on the TSB & PCV/valve cover fix.

Thanks All!

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