Just bought a 2012 Z-something Tahoe and may have lied to by dealer? An engine idle thimg.

[MarvinVR]

OK So Im 71 --an old wrench and in the 70s used to tune my 350s so well you could stand a nickle on its edge on the air cleaner. Had many cars from many makers all these years but never new ones, always good used. Never had a 5.3 chevy block. So I get a helll of a deal I thik, 2012 ZR1 loaded, beautiful exterior looks like new, Interior an 90 on a 100 just because carpets a bit off color, 116,000 miles. Heres the thing--at idle, its a tad jumpy. Maybe most know nothing drivers wouldnt even notice but my 29 year old daughter did and I certainly did...like a tiny miss. The dealers mechanics said "So many people ask us about that---its perfectly normal for that 5.3 engine, trust us." Hmmm o late I bought it as is. Did I screw up?

 

[kbuskill]

If it were a consistent misfire it should turn the check engine light on.

I would suspect that it probably needs a set of plugs and/or wires at 116k miles. The service manual doesnt call for the first spark plug change until 100k miles so it probably never got done before they traded it in.

Could also just be bad gas or the injectors might need some cleaner ran through them.

If it is a Flex fuel truck, with the yellow gas cap, wait until you are close to empty and then get about a 1/4 tank of E85 and drop a big bottle of injector cleaner in the tank. Run it until close to empty and then fill up with the E85 again and run it for a tank. The ethanol does a pretty good job of cleaning things up.

Also, now is the best time to have the AFM (active fuel management) turned off either with a tune or some kind of disabler. Also, the torque converters on the 6L80E transmissions are a weak point so keep that in mind. A proper custom tune will prolong the life of the engine as well as the transmission and torque converter.

 

[Doubeleive]

OK So Im 71 --an old wrench and in the 70s used to tune my 350s so well you could stand a nickle on its edge on the air cleaner. Had many cars from many makers all these years but never new ones, always good used. Never had a 5.3 chevy block. So I get a helll of a deal I thik, 2012 ZR1 loaded, beautiful exterior looks like new, Interior an 90 on a 100 just because carpets a bit off color, 116,000 miles. Heres the thing--at idle, its a tad jumpy. Maybe most know nothing drivers wouldnt even notice but my 29 year old daughter did and I certainly did...like a tiny miss. The dealers mechanics said "So many people ask us about that---its perfectly normal for that 5.3 engine, trust us." Hmmm o late I bought it as is. Did I screw up?

Really hard to say, could be nothing could be a injector could be a spark plug could be a coil pack. Getting to the bottom of it requires a deeper look

 

[kbuskill]

I forgot to mention, these trucks use hydraulic engine mounts, picture a thick rubber balloon filled with oil. They are also prone to tearing and leaking the oil out. Alot of guys, myself included, replace them with old school solid rubber mounts which are much more durable. Some people say they can feel the engine vibrations more with the solid rubber mounts, I can't really tell a difference. You could have a bad mount causing excess vibration to be transmitted, or someone could have replaced them with a solid mount, although that seems unlikely.

 

[Hey you]

Bought my '15 LT with 125K just over a year ago, 140K now... same thoughts as you with similiar symptoms. There are several rabbit holes you can go down, tranny, injectors, plugs/wires, lifters, etc...
Like you I used to enjoy wrenching, but now it's harder due to age and CRS! The 5.3 is a good motor, just needs a little TLC. Don't get in a hurry, but getting things working smoothly will take time. Plugs/wires/coils, Tranny fluid/filter, Injector cleaner, and the trans temp module bypass are what I would start with.
This is a great site for help, these guys know these vehicles and are always willing to help.
Welcome!

 

[intheburbs]

If it was missing, you'd see a check engine light. It flashes when the computer detects a misfire.

 

[alvocado]

Mine was a little jumpy at idle with 70k on my last set of plugs. After new plugs and wires, it's so smooth that I can't tell it's running at a stop light. Still running factory coils with 233k miles.

 

[Joseph Garcia]

Welcome to the Forum from NH. Many old wrenchers on this Forum.

Lots of knowledgeable folks here who freely share their knowledge, experiences, and perspectives. Knowledge is power.

I hope that you will become a participating member in the Forum's discussions.

Pics of the truck, please.

You are already receiving sage advice from the knowledgeable folks on this Forum.

You are most likely already fully aware of this as an old wrencher, but I'll offer it anyway..... Do you have, or have access to, a quality bi-directional scanner? If not, I recommend that you get yourself a quality bi-directional scanner to add to your tool box. Then, you will be able to read ALL trouble codes, along with a brief explanation/pointer to the source of your issue. You can test many of the truck's electronic functions with the scanner, in order to determine the source of an issue.

I believe that this is what @Doubeleive implied, when he said that you'll have to dig deeper. In your case, you'll be able to monitor the firing of all cylinders in real time and better be able to see where your idle firing interruption is coming from.

 

[Fless]

You are most likely already fully aware of this as an old wrencher, but I'll offer it anyway..... Do you have, or have access to, a quality bi-directional scanner? If not, I recommend that you get yourself a quality bi-directional scanner to add to your tool box. Then, you will be able to read ALL trouble codes, along with a brief explanation/pointer to the source of your issue. You can test many of the truck's electronic functions with the scanner, in order to determine the source of an issue.

I believe that this is what @Doubeleive implied, when he said that you'll have to dig deeper. In your case, you'll be able to monitor the firing of all cylinders in real time and better be able to see where your idle firing interruption is coming from.

^^ This. Put a good scanner on it and monitor the individual cylinder misfire counts and go from there. Engine and transmission mounts can also wear out, so that might be what you're feeling.

 

[j91z28d1]

honestly, it's probably fine. every ls engine I've been around idles like it's missing every like 3rd or 4th hit at idle.

you're just from the time that a small block chevy would idle like a rock at 700rpm but cam died out at 4k on a good day. these days they idle in gear at 500ish rpm and pull cleanly to 6k making power. the trade off is the bump around a bit.


unless you see a flashing check engine light on the dash from a active miss fire. engine your new to you truck.

 

[Doubeleive]

YES.... a deeper look, closer look, a graphic readout on a electronic device lol
sometimes we can feel things that do not clearly show up as a check engine light, at least I can
like balancing a nickel on the air cleaner, my butt sensor is sensitive
and even though I normally blast music loud enough to hurt my ears i can still hear when my engine or anything on the vehicle makes even a tiny bit different noise or sound

 

[solli5pack]

If the motor mounts are original can't hurt to replace them. That might smooth it out a bit.

 

[j91z28d1]

If the motor mounts are original can't hurt to replace them. That might smooth it out a bit.

I forgot about this... yeah, most likely toast

 

[MarvinVR]

According to dealer it had new plugs and wires about 20K ago along with injector cleaner, all fluids replaced even rear, This is more like a tiny miss than something like jumpy from bad mounts, though now I do want to change those. One of you said: "Also, now is the best time to have the AFM (active fuel management) turned off either with a tune or some kind of disabler. Also, the torque converters on the 6L80E transmissions are a weak point so keep that in mind. A proper custom tune will prolong the life of the engine as well as the transmission and torque converter. 1. AFM? Can I turn that off? what is it and do I even need it? 2. Custom tune--who would I go to for a custom tune and what would I tell them I want? I could put a chip on it like on my 01 ford diesel. (Sorry for the curseword F O R D )

 

[MarvinVR]

OUCH I had no idea--just did afm research? Do all 2012s 5.3s have that? I wouldnt ever want that thing on. But in reesearching how to disable it I got this: "

• AFM Delete Kit:
  A more comprehensive solution that replaces the AFM components with standard ones.
  
  • Benefit: A permanent fix that removes the AFM system entirely.
  • Consideration: Requires a more involved installation process, often including replacing the camshaft and lifters, and requires an ECU tune.
    

Alternatives offered were a thing that plugs into the computer port but draws power whan engine is off

 

[MarvinVR]

Oh just found this in a chevy truck site
The 5.3L has Active Fuel Management, which cuts out 4 cylinders in an effort to save fuel. However, it has shown itself numerous times to be poorly designed and thought out, and left unchecked it will eventually cause oil burning. If you'd like a more detailed description of what happens and why let me know, but trust us AFM is BAD NEWS. Your truck should be fine as it's got low mileage so there is time for you to eliminate it and enjoy the truck for many years and miles.

Our advice for everyone on here is to spend a few $ up front to save a headache later. Buy yourself a Range AFM Disabler Device from Range technologies ($200 & plugs into your OBD-II Port full time). It will keep your truck running on all 8 cylinders at all times, thus preventing the myriad of issues that come along with shutting down 4 of them.

Another (and more fun) option would be to purchase a Diablosport Intune I-1000 tuner and use it to turn off AFM. This also gives you the option of adjusting your shift firmness as well as choice between several engine tunes that add power and Tq. However, using this option requires some additional attention; if GM sees you've modified the vehicle's ECM programming, they will void your warranty. This can be prevented by returning the vehicle to stock tune prior to a dealer visit, but some folks see this as an issue.

Regardless of which AFM disabling option you choose, you may also wish to purchase a PCV (positive crankcase vent) catch can. This will keep oil vapor, condensate, and a bunch of other junk from getting into your intake. This helps prevent any additional oil burning as well as keeps your intake much cleaner.

Finally, since you just bought the truck (and you may not need us to tell you this but it's good practice) make sure you clean your throttle body & MAF sensor. https://www.holley.com/platform/chevrolet/tahoe/2012/products/tuners_and_programmers/

 

[MarvinVR]

https://www.edgeproducts.com/platform/chevrolet/tahoe/2012/engine/325-5-3l-v8/ they recommend this tuner if you dont want to keep one in you obd port
Edge EvoHT2 - California EditionGas and Diesel Vehicle Tuner - 50 State Legal
Part# 86040
In Stock

(7)
Free Shipping

$449.95

What you folks think?

 

[MarvinVR]

Wow you guys opened my eys to a lot of stuff about these. Im used to hanging in a site where we ford diesel owners constantly suffer with a myriad of problems LOL. After researching all Ive said above I went to amazon and simply wrote afm disabler and found a bunch as low as 49 bucks!! Why wouldnt I want one of those instead of 219 to 259 for a Range brand? And I read a lot about pcv catch cans being a good thing to have. I have a terrible feeling you guys are going to be seeing a lot of me as Im a research fool. I own 6 firebirds from 1997 to 2002 with a WS6 LT1 and Holy cats did GM do shoddy work in the late 90s. I aint going to be a newbie for long.

 

[EddieC]

I've gotten into more trouble than I care to remember buy fixing things that aren't broken.
A little idle variation would be one of those things for me to ignore at "our" age.

 

[homesick]

I've gotten into more trouble than I care to remember buy fixing thing that aren't broken.
A little idle variation would be one of those things for me to ignore at "our" age.

LOL, it's probably just our ears cutting out.

joe