07 Sierra Smoking

Danielmattingly · February 25, 2010

Oh I'm having some issues with my 2007 Sierra z71 5.3 "new style"

Its been using oil about a quart every 4k..I'm getting sick & tired of being told by the Dealer that its "normal"... Every chevy I've owned has never burned any oil.. I always run synthetic..always mobil 1..I take very good care of my trucks.. It runs & drives fine but this is what I've noticed with it..it wouldnt bother me so much if it was just simply using it..From what I've read so far on other posts nothing seems to match up with my problem..

When I let it coast downhill for a mile or two with my foot completely off the gas pedal the whole time & when I push back down on the pedal blue smoke will pour out of the tail pipe..It seems the longer I let it coast the more it'll smoke..Its getting oil into the intake manifold & its burning it off..then after maybe 2 seconds or so it'll clear up & it will not do it again unless you coast a long distance..I've notice that it has to coast at least half a mile with your foot off of the gas to do this...

Any ideas? PCV valve? I have no idea where they are located now..I have poeple trying to tell me its the valve seals..But if that was my problem shouldnt it be smoking when I first start it in the morning?

Other than that I cant get it to smoke any other way..You could tach it up to 5 grand & it wont smoke..

Its got 158,000 on it now & its been doing this for about as long as I can remember..Its never gotten worse than 1 quart every 4k..

I'm getting very sick of carrying oil around with me & its embarrasing to have a newer truck that smokes..

I love the truck it goes great.. all highway driving...I'd like to figure out the problem & keep driving it till 200k

KMGZ400 · February 25, 2010

whoa... that truck has 158k miles on it?

09Jimmy · February 25, 2010

You're correct, if it was the valve seals it would smoke on startup. It's drawing oil into the intake manifold under high vacuum conditions, i.e. coasting. GM has a revised passenger side valve cover with improved oil baffles and PCV but it hasn't helped my truck. I would suggest you install an oil catch can in the PCV hose that comes from the passenger side valve cover to the intake tube. This will capture the oil in the cannister before it gets into the intake and burns.

GM - some assembly required.

Danielmattingly · February 25, 2010

whoa... that truck has 158k miles on it?

146k in that picture

pm26 · February 25, 2010

My 1999 Mazda 626 V6 is using about 1 quart of oil every 3 k miles, but I have never seen any blue smoke from the exhaust . The motor has 243k miles on it and runs strong. There are no oil leaks. I am not worried about 1 quart every 3k at this stage.

Zembonez · February 25, 2010

Have you pulled the plugs and had a look at them? My bet is a cracked oil ring in one cylinder. I've seen it in a 5.3 twice. One only had 30K on it and GM replaced it. The other one was high mileage but I don't know exactly how high.

Both engines had one plug that was black and oil fouled and all of the others were clean and a little gray (normal). I'd pull them and have a look,.

truckofwinandawesome · February 25, 2010

does that 5.3 have those 3 magic letters known as A-F-M?

Danielmattingly · February 25, 2010

does that 5.3 have those 3 magic letters known as A-F-M?

Yes it does have the annoying AFM..I've looked into buying a tuner to disable it but i have never gotten around to it..

I'll pull the plugs sometime this weekend just for kicks & giggles but if it was a cracked oil ring shouldnt it smoke more? esp under high rpms?

Zembonez · February 25, 2010

does that 5.3 have those 3 magic letters known as A-F-M?

Yes it does have the annoying AFM..I've looked into buying a tuner to disable it but i have never gotten around to it..

I'll pull the plugs sometime this weekend just for kicks & giggles but if it was a cracked oil ring shouldnt it smoke more? esp under high rpms?

Not necessarily. The coasting you describe (with the throttle closed) would create vacuum in the cylinder that could pull oil up from the crankcase. I'm not saying this is what has happened but I have seen it twice.

Z'06 · February 25, 2010

You're correct, if it was the valve seals it would smoke on startup. It's drawing oil into the intake manifold under high vacuum conditions, i.e. coasting. GM has a revised passenger side valve cover with improved oil baffles and PCV but it hasn't helped my truck. I would suggest you install an oil catch can in the PCV hose that comes from the passenger side valve cover to the intake tube. This will capture the oil in the cannister before it gets into the intake and burns.
GM - some assembly required.

Caution - you may awaken the occasional "expert" around here who believes that if the engineers designed it that way from the factory then it cannot be improved upon.

To the OP, look into a catch can as 09Jimmy suggests, and consider turning off "All For Marketing" with a PCM tune, if not to improve your remaining time of ownership, then perhaps for the benefit of a fellow human being who later buys your truck from you.

rodram · February 25, 2010

I read these threads about oil consumption .... most of them are '07's with 5.3L AFM, and GM giving bs explanations telling owners that oil consumption of up to a quart in 1500 miles is 'normal' or 'as expected'

I have read that oil consumption causes may include:

- overactive lifters... whatever that means

- the newer PCV configuration

... but the oil consumption is a symptom of the problem .... not the problem itself.

I have read that the engine designers are looking at the effects on the cylinder walls and the lifters caused by the rapid cooling in the cylinders that are temporarily shut down when AFM kicks in ...

... for me, I'll just stick to my '97 5.7L Vortec ... (it ain't perfect, but I have the big expensive bugs fixed) and I expect it to keep me going for a long time to come .... if anyone hits my truck and causes an insurance write-off, I'll be ready to strangle them right at the accident site

redvett · February 25, 2010

All reciprocating piston engines burn oil. 1qt per 4000 miles is very good and most use about 1 qt to 3000 mi. If you expect to drive your vehicle 7-8000 miles without using oil its never going to happen. The PCV system has a fixed orifice to control oil usage through the PCV system.

Col_Sanders · February 25, 2010

All reciprocating piston engines burn oil. 1qt per 4000 miles is very good and most use about 1 qt to 3000 mi. If you expect to drive your vehicle 7-8000 miles without using oil its never going to happen. The PCV system has a fixed orifice to control oil usage through the PCV system.

BS. Burning a little oil is normal but I dont think 1 quart every 3k is acceptable on a new vehicle. I have had my Mazda since 0.4 miles (now just shy of 69k) and it has not used any noticeable amount between changes. I run Mobil 1 5W-20 and Wix filters and change every 6-7k miles.

I do the same with my Sierra and have put 12k on it so far. It has used over 2 quarts in that time but I dont ever notice smoke. Its an 07 5.3 with AFM and sees pretty much all highway use between 55-70mph. AFM may or may not be the cause of it, but I will have it disabled when I get a tune and see if it helps.

rodram · February 25, 2010

All reciprocating piston engines burn oil. 1qt per 4000 miles is very good and most use about 1 qt to 3000 mi. If you expect to drive your vehicle 7-8000 miles without using oil its never going to happen.

.... says a 5.3L owner that is experiencing massive oil consumption