Long-time Trailblazer EXT owner loves driving "old junk"

[spfautsch]

Just dropping in an introduction. Already posted to an old thread in the GMT360/370 Tech forum on a TCM issue I'm having on my recently acquired 5.3 Envoy XL.

I bought my wife an Atlas powered '06 Trailblazer almost a decade ago and we've enjoyed it thoroughly. I've done extensive maintenance on it, and we've loved the vehicle a lot. It's been our family truckster for vacations to the sunshine state ever since. As my two other personal vehicles (a built 1995 and mostly stock 2001 Corvette) aren't terribly practical for winter driving, I started looking for another GMT 3xx vehicle late last fall, and stumbled across the aforementioned 5.3 powered Envoy XL for a price I simply couldn't pass up.

Obviously it had a bunch of deferred maintenance, which I've been catching up on over the past 5 weeks. New exhaust manifold due to broken exhaust bolts, leaking oil pan, leaking front diff seals, faulty rear HVAC blend actuators, completely discharged refrigerant due to leaking high-side service port, the list goes on. Also no shortage of lazy-pro-mechanic-caused problems.

If I didn't really love how spacious and comfortable these vehicles are I'd have looked for something else, but aside from the rust spots, this one seems to be worth the effort to get back up to snuff.

 

[Mooseman]

Welcome to the Nation! You're in the right place. Post a pic of her, warts and all. We promise we won't laugh. We've all been there.

 

[spfautsch]

Thanks Mooseman! It's been a "b" of a winter up until the middle of last week so I haven't even washed her since she's been in service. As soon I as I can get the girls cleaned up and together for a photoshoot I'll post something.

Having read a lot on the subject, I'll be posting a "survey" thread asking who has the most miles on their DOD / AFM enabled engine as mine w/ 195k seems to be holding it's own.

I also probably have some transmission building insight to offer. The boost valves GM put in these are completely inadequate for one of these with less than 3.73 final drive gearing. Not to mention the 10k lb hitch receiver that was standard equipment sending completely the wrong message to owners.

 

[TollKeeper]

You didnt mention what year the new Envoy was?

I have thoroughly loved my Envoy XUV. I just Semi-Retired her to backup duty. But she is a true trooper.

I bought it from a neighboring city to you, where I used to live, St Peters, MO.

 

[spfautsch]

LOL, both the "new" and "old" are 2006 model year. The I6 Trailblazer we've had since 2014 has made at least 13 trips to the sunshine state and is coming up on 214k miles, and the 5.3 Envoy just rolled over 196k today.

Our Trailblazer has also been a great workhorse. Whether I need to haul a snow blower, or 5 (or even 6) old fat guys (to be polite let's call them classmates), it's never let me down. The only complaint I could possibly lodge is that you can't get a full sheet of plywood / osb in them.

I found the Envoy on craigslist for sale by a really nice couple in House Springs, MO. Probably only the third of several dozen craigslist listings I've put time into that didn't destroy my faith in the future of humanity.

After a 150+ mile drive today taking the in-laws to a dr appointment in the Envoy I'm thrilled to see zero drops of oil under it. So happy that the nasty and nearly 12 hour job of replacing the oil pan gasket wasn't wasted effort.

 

[TollKeeper]

So on the issue of the AFM/DOD, if it hasnt already been replaced with a DOD/AFM delete kit, my suggestion would be to get the ECM tuned, to disable it. This doesnt make the problem go away, as the "weak" parts are still part of the system, but it makes it so the computer can no longer activate it.

@limequat, a member here, does the tune, and can do a few other things while in there. I had him do it on my Saab (RIP), and it worked flawlessly... Until the head gasket decided to go.

My 2006 Saab had 162k miles when it failed. I have seen them fail as low as 60k miles, and as high as.. Well never. Its usually a matter of not if, but when, it will fail.

Edit: Frequency of oil changes (never over 3000 miles), Oil Changes, High Quality Oil, and High Quality Oil Filters are the key to a AFM/DOD system lasting. But even then it isnt guaranteed.

 

[spfautsch]

Thanks for the pointers on the tuning, if I do a delete I may just look into having someone else handle it so that's good to know. I have a MDI1 clone but haven't quite brought myself up to speed on what is involved in tuning a CAN vehicle. More familiar with the class 2 stuff and older flash based controllers (and open source software for them).

I'm somewhat on the fence as to whether I want to delete AFM or not. It's definitely still active as I had the intake off and noticed the VLOM and the exhaust note changes noticeably when it activates. Just wish I'd known about cleaning the screen when I had the intake off.

I've since read a bunch on the subject and understand the why and how of failures - sticking in the bore or having the locking pins get mangled due to a mistimed lock / unlock event. Judging by the sludge I cleaned out of the oil pan I don't think good oil has been a staple in this vehicle. I learned in my teens the value of fully synthetic oil (Mobil1 only) and haven't strayed from it since. After 26 years and over 700k miles of commuting across three different vehicles I've never had any internal engine issues.

Hopefully ol' Rusty will get me through winter before she needs more $$$ spent. I suppose if I get to a point where I need to pull the heads, a set of regular lifters and possibly a cam will be in order "while I'm there".

 

[Mooseman]

Another method of disabling DOD/AFM is a Range type device that plugs in the OBD. It will stop it from activating so should prevent an activation/deactivation failure.

Amazon.com : afm disabler

 

[spfautsch]

Finally got around to washing her. TCM module appears to have fixed the issue I revived someone else's old thread about here:

Prndl going crazy

a 2005 GMC envoy xl Denali. I purchased it a few months ago and has been fantastic until a few days ago. In park it runs great and has no issues. When put in gear and after driving a mile or 2 the prndl jumps from what ever gear you are in to park and back, rapidly until you shut it off for a...

gmtnation.com

 

[TollKeeper]

Truck looks good!

 

[spfautsch]

Thanks! I'm all-in for around $4000 on this one (including tires, which I normally consider a consumable). You can't see the rusticles on her - left rear quarter and right rear fender as well as the bottom edge of 3 of the 5 doors. But she otherwise rides and drives so nice I'll probably get in trouble for coasting into speed zones 15+ over because it's so smooth and quiet.

I'm sure there will be other minor repairs needed along the way, but the major items remaining are an AFM mechanical delete and maybe next fall I'll build the trans to be able to give me another 200k miles.