Stabilitrak issue my journey so far.

[Taheezy_88]

Two weeks ago after placing 22inch rims with 33 inch tires I have been dealing with this issue. Engine code to begin with was P0621

First part I thought it was due to the new wheels and tires setting off the stabilitrak sensor. Ive resetted my abs system countless times and even today attempted again to just see if it work it didnt. When the "stabilitrak" first started I was getting "low engine power service engine" error on my dash so I followed the repairs.

Second part Full Tune up. I replaced Throttle body, MAF sensor, Plug wires, NGK iridium plugs, Alternator, belts just cause. (coil packs are on the list but see problems later) One fix seem to lead to another with the "stabilitrak" coming and going between each repair.

Third part Today driving after the second day of my tune up I felt i solved everything Truck was running strong. Later on in the day driving on the freeway I see the dam STABILITRAK Service tire system? but this time NO ENGINE LIGHT. I pull over unplug my battery try to restart cpu. Nothing works, I drove the care home slowly through back roads about 4 miles(i live in rural CA) When I get home I just said heck with it and Ibought a 350$ obd2 scanner.

4th part last diagnosis before this post. OBD2 determines a misfire in cylinder 4, I have an incredible knock in the engine now even louder with rev up. I am completely determined my lifters are done and top end rebuild is now in place.

I hope this post can shed some light to this problem and see that this error can lead to multiple different problems rather plugs, to who know what my problem is yet.

My question is anyone know of some good top end rebuild parts, performance based, forums where it has been done, parts list, etc..?

Guess my question is If im going to rebuild this I want to have a performance rebuild and any recommendations are welcomed thank you and sorry for the grammar.

 

[Taheezy_88]

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[wjburken]

Welcome to the forum from Iowa.

Sorry to hear about your issues.

There are a number of folks here that have gone down the path you are on. @iamdub has a good build thread that documents his AFM delete rebuild. There are others, but I am drawing a blank at the moment.

Might share a little more about your vehicle like year, motor, miles, other upgrades or work done, etc. What do you consider a performance build?

Would also be helpful if you shared more about the codes you were getting as you may have other things going on as well. I can’t say I’m familiar with the P0621 DTC code.

 

[Taheezy_88]

Welcome to the forum from Iowa.

Sorry to hear about your issues.

There are a number of folks here that have gone down the path you are on. @iamdub has a good build thread that documents his AFM delete rebuild. There are others, but I am drawing a blank at the moment.

Might share a little more about your vehicle like year, motor, miles, other upgrades or work done, etc. What do you consider a performance build?

Would also be helpful if you shared more about the codes you were getting as you may have other things going on as well. I can’t say I’m familiar with the P0621 DTC code.

Hey thank you for the response.
Current is 2007 tahoe 5.3l LT 4wd
No mods except aftermarket Carven exhaust
22 inch wheels 33inch tires can get the tire spec tomorrow
I run aggressive as you can tell by my looks and anything performance wise that adds HP and of course quality is what I want. This is my work/family truck so I'm willing to go the extra mile on parts for it just looking for the right direction. Mechanically I'm handy done some rebuilds and always maintain my own.
Miles 147k always maintained
P0621 only code I've been throwing and low oil pressure from time to time.

 

[Taheezy_88]

How do I tell if my 5.3 is vvt or non vvt? Is 2010+ a good standard for vvt engines and any year below is non vvt?

 

[wsteele]

How do I tell if my 5.3 is vvt or non vvt? Is 2010+ a good standard for vvt engines and any year below is non vvt?

2010 on for VVT on your model.

Here is a link for the DTC, https://www.obd-codes.com/p0621

Before pulling the heads, I would pull a valve cover and make sure you actually did have a dead lifter on number 4. You very easily could have gotten a bad plug/wire, etc. with all your parts replacing.

Good luck.

 

[iamdub]

Throwing a ton of parts at it semi-aimlessly can bury the problem deeper rather than fix it and it can cause other problems. Just because a part is new doesn't mean it's "good". This is especially true with cheap aftermarket electronics (sensors, plug wires, etc.).

First off, we need to clarify the events and when they happened. This is the timeline I'm understanding from your post:

1) All was well and you installed new wheels and tires

2) Soon after, got a P0621 (I'm showing that to be for a fault in the charging circuit light, as in a dead bulb in the cluster)

3) Tahoe started going into "Limp Mode" (Service Stabilitrak and Reduced Engine Power)

4) You replaced a bunch of tune-up-related parts and found no stable improvement

5) It ran fine for a couple of days then the Stabilitrak message popped up again

6) You bought a scanner and found #4 misfire and then noticed a "knock"


^^^ Is this accurate?

First thing I'd do is double-check my work. Were the plugs gapped properly? Make sure the spark plug wires are fully locked in. While you have your hands on them, do a quick test by swapping the #4 wire with one from the opposite bank and see if the misfire follows or goes away entirely.

 

[Joseph Garcia]

Welcome to the Forum from NH.

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.

You are already receiving responses to your inquiry, and other folks will chime in.

 

[Doubeleive]

for that p0621 you may want to double check your connections on the alternator and battery and/or the replacement alternator could be defective
this guy goes real deep into it, but the end result was a bad alternator

 

[Taheezy_88]

Yes timeline is correct. Thanks for the response. I have installed these parts over a two week timeline only replacing one to replace another. I got most of that advice from here TB, Plugs, Wires, MAF, Alternator, etc. One part to another.I'll check my plug on #4 and pull the cover.

 

[Taheezy_88]

no more p0621 i pulled alternator the other day and had it checked before replacing plugs and wires.

 

[Taheezy_88]

Pulled #4 plug earlier checked gap, and reseated the plug wires also. Still misfire but now just p300.

The knock is a knock and louder with rev up. It isn't no tick sound its a knock guys. How can I post a vid?

 

[Just Fishing]

Youtube, then post a link or imbed the video using the little button when posting:

and that service stablitrack crap comes on with just about everything.
Usually something disconnected.
me not plugging in my displacement on demand connector on the back of the engine vally cover triggered that, along with ABS errors for some strange reason.

Also if you moved your throttle body butterfly while say cleaning it...
That will also trigger all sorts of errors.
I had that surprise when i put my engine back together.

 

[iamdub]

Pulled #4 plug earlier checked gap, and reseated the plug wires also. Still misfire but now just p300.

The knock is a knock and louder with rev up. It isn't no tick sound its a knock guys. How can I post a vid?

Uploading to YouTube and posting the link is all I know for posting vids.

Check the dipstick for sparkles in the oil and rub it on a white napkin to see if there's anything alarming. Pop off that passenger side rocker cover and see if you have a limp rocker. If you have a lower end knock, it may be too late. Sometimes a collapsed lifter can sound like a knock, especially if it rotated.

 

[Taheezy_88]

Pulling apart today. Opting for maybe a new engine instead of rebuild.

 

[jj88]

Did you calibrate your PCU when you got the 33" tires? stock tires are 31.6" in believe. I will be using this speedo calibrator soon myself. I think I read somewhere that 3% off in diameter will set speed sensor codes, and other things connected to wheel speed sensors, etc. I'm hoping the speedo calibrator will fix this.



http://www.hypertech-inc.com/vehicle-results.aspx?AAIAID=188054

 

[1BADI5]

Sadly, tire size going to have nothing to do with a misfire.

If your 900 is a 2010, more likely then not you have a LMG 5.3, so you will have VVT and AFM/DoD.

IF you go about replacing the motor, I would recommend buying a long block from a quality/well known shop. It will cost you alittle bit more up front, but will last longer then a used motor. Got one that has had the VVT and AFM removed and you'll be on easy street....but it will require a tune to run.

 

[wsteele]

Sadly, tire size going to have nothing to do with a misfire.

If your 900 is a 2010, more likely then not you have a LMG 5.3, so you will have VVT and AFM/DoD.

IF you go about replacing the motor, I would recommend buying a long block from a quality/well known shop. It will cost you alittle bit more up front, but will last longer then a used motor. Got one that has had the VVT and AFM removed and you'll be on easy street....but it will require a tune to run.

I think he said his rig is a 2007, so yes on AFM, no to VVT.

I agree on the quality long block, he can buy a reman for around $3K (plus core), some offer AFM Delete as part of the package and include a Diablo Predator to turn off AFM in the PCM after the engine is in the truck.

 

[Taheezy_88]

Quick update guys and thanks for the replies.

I pulled intake manifold, and valve covers. Driver side rocker arms and rods look good all intact.
Passenger side I have one loose rocker arm above cylinder 4 where I was getting a misfire.
First pic is drive side and second is passenger. My finger is where the loose rocker arm is at.

Being as far in the tear down should I opt for the AFM DOD delete? Or replace rockers and rods?

Side note: I was having oil pressure issues before this happened. What replacement route to fix that issue? New pump or just the oil sending sensor deal in the back of the manifold?

 

[iamdub]

Quick update guys and thanks for the replies.

I pulled intake manifold, and valve covers. Driver side rocker arms and rods look good all intact.
Passenger side I have one loose rocker arm above cylinder 4 where I was getting a misfire.
First pic is drive side and second is passenger. My finger is where the loose rocker arm is at.

Being as far in the tear down should I opt for the AFM DOD delete? Or replace rockers and rods?

Side note: I was having oil pressure issues before this happened. What replacement route to fix that issue? New pump or just the oil sending sensor deal in the back of the manifold?

View attachment 271728 View attachment 271729

Since the intake manifold is off, check the VLOM bolts to make sure they're tight. It's also a good time to replace that oil pressure sensor and clean or replace the screen under it. The sensor may not be bad, but it's really hard to access with the manifold in place. A loose VLOM can cause low oil pressure and a failed AFM lifter. A leaky O-ring is another common cause for low oil pressure, but you can't check that unless the engine is running.

As far as the rocker, you gotta determine why it's loose. Is the pivot bolt loose? Is it slack between it and the push rod (collapsed lifter)? If a collapsed lifter, and since the the VLOM is accessible/removable, you can try this trick:

Try to see if that lifter isn't turned and if the cam lobe is ok. If so proceed with trying to unstick the lifter. If that fixes that, disable AFM ASAP! You can get it disabled in a tune for $50 plus the shipping of your PCM.

You're really not that far into an AFM delete. If I had to put a number on it, I'd say you're around 15% "there".