Oil pressure issue

[2006Tahoe2WD]

Do you have a recommendation on a scanner to get?

I have a OBDLink MX+ and an iphone. I think I have the app loaded that is recommended but I understand that other software can be used. This will allow you to look at and graph in real-time many different PIDs.
I've had other scanners but I returned them for various reasons.

 

[2006Tahoe2WD]

One thing to remember is take the time to make sure things are diagnosed properly before throwing parts at it. The metallic ticking you describe, is often nothing more than an exhausting between the exhaust manifold in the cylinder head. They can sound just like a lifter ticking. Look for a missing or broken exhaust manifold bolt as well.

Good point. I think it is about 99% you will have broken exhaust bolts sooner or later. I had one (broken bolt) and installed one of those aux. plates. So far so good after 30k or more miles.

 

[DSRBLDR47]

I've got two broken exhaust bolts on my 2002 tahoe. Been that way for years and so far no leaks. I haven't done any checking on the 2010 but it really doesn't sound like exhaust, and the noises vary in timing seemingly at random. Its coming from the passenger side. It really does sound like its coming from the starter/ring gear.

In looking at the VLOM in the valley cover and a few videos I saw one that describes a small sleeve that gets inserted in the oil feed that feeds the channel for the four oil solenoids for the DOD lifters. The sleeve blocks off the passage, and the solenoids go bye bye. Do the DOD lifters "activate" at the presence of oil pressure, or lack of? I would think shutting off pressure makes them collapse and that drops the cylinder.

 

[j91z28d1]

I've got two broken exhaust bolts on my 2002 tahoe. Been that way for years and so far no leaks. I haven't done any checking on the 2010 but it really doesn't sound like exhaust, and the noises vary in timing seemingly at random. Its coming from the passenger side. It really does sound like its coming from the starter/ring gear.

In looking at the VLOM in the valley cover and a few videos I saw one that describes a small sleeve that gets inserted in the oil feed that feeds the channel for the four oil solenoids for the DOD lifters. The sleeve blocks off the passage, and the solenoids go bye bye. Do the DOD lifters "activate" at the presence of oil pressure, or lack of? I would think shutting off pressure makes them collapse and that drops the cylinder.

the lifters release and collapse with oil pressure applied to the ports in the lifter valley. that's why he will also tell you have to cut the gasket on those ports to vent any oil pressure backing up. Just to make sure they don't collapse ever again.

I know everyone worries about oil leaks from there causing low pressure but my experience it doesn't lower it at all. I still have 40 plus at hot idle with cut gaskets.

 

[rdezs]

It's when the solenoid activates to turn on AFM that it sends oil pressure. AFM is deactivated it won't really matter, unless the solenoid is leaking internally. Which is something I haven't seen yet.

I tried multiple scanners, the Diablo sport predator is very convenient to turn off AFM and tighten up the shifting for long transmission life. Got rid of all my bidirectional scanners I tried once I picked up a tech 2. Haven't found anything that comes as close as GM's own tool

 

[j91z28d1]

the afm lifter can actually vent oil from the lower port up thru the top port, if blocked up the afm lifters releases.

I'm stock form the solenoids vent the lifter side when off. if the vent ports get clogged it can cause the same issue as putting a smooth afm delete plate on without replacing the afm lifters. the engine runs a few minutes and a afm lifter collapses

 

[Musicars]

Regarding the original low oil pressure issue; I posted on here a few years about a low pressure issue in my '06 Denali. I did the sending unit, the o-ring, the pump, connected a gauge down where the oil cooler lines were and verified it really was low. Nothing worked, had about 8-10 lbs of pressure when warm. I then sent an oil sample in for testing (Blackstone testing I think). They verified bearing material in the oil.
I then picked up a lower mileage engine and got that ready to put it. In the meantime I started using 40 and 50 weight Mobile 1. Can't remember when this started but I drove it for at least 4 years with low pressure and the warning only went off on hot summer days. Never got that newer motor in. Truck got stolen this March. Probably stole it for the motor.

 

[DSRBLDR47]

It's when the solenoid activates to turn on AFM that it sends oil pressure. AFM is deactivated it won't really matter, unless the solenoid is leaking internally. Which is something I haven't seen yet.

I tried multiple scanners, the Diablo sport predator is very convenient to turn off AFM and tighten up the shifting for long transmission life. Got rid of all my bidirectional scanners I tried once I picked up a tech 2. Haven't found anything that comes as close as GM's own tool

I have a buddy at work that has HPT tuners so I don't really need that part. I do plan on having him do the DOD delete and torque converter lockup tuning. I just want to see whats going on, and see the status of the monitors so I can know if its ready to be smogged (gotta live in commiefornia for the time being!). I'm just trying to learn how the system works, and if I do pull the valley cover off to check for any oil leaks, what I can or should do to disable the DOD while I'm in there. From what I've gathered so far, a lack of oil pressure (for whatever reason, broken o-ring on the oil pickup tube?) won't cause the DOD lifters to go rogue and collapse and in essense activat DOD. What has been suggested, since there is a power loss associated with the lost oil pressure, is that the lost oil pressure is screwing with cam timing/vvt and causing the power loss. Does that make sense?
Thanks for any info!

 

[j91z28d1]

the ecm can read oil pressure and won't do vvt or afm if the oil pressure light is on code set.


these things min spec for oil pressure is something like 6psi hot 1000 rpm. very few people have actually low pressure by gm specs. it's probably slow for other reasons, being fuel or air.

check with hpt your alcohol content. if running e5 gas and it reads 50% it will run super rich and slow.

the same guy that shows the oil block off to afm shows how the afm lifters work by taking them apart if it helps with the understanding

 

[DSRBLDR47]

So even the vvt mechanism isn't affected by low oil pressure?

 

[rdezs]

The BBT requires a certain amount of oil pressure and volume

 

[j91z28d1]

So even the vvt mechanism isn't affected by low oil pressure?

hpt and most decent scanners should read the cam position to know forsure. as well as show the parameters that need to be met to activate


do you have a low oil pressure code light? I'm not around my software, so someone else can probably copy and paste the specific pressure vs rpm min spec but I'm going to say you won't feel a few deg of cam timing. and look it up, but I think the default is normal and vvt moves it up help low rpm tq by max of like 15ft lbs at part throttle. if you're feeing power loss at wot, especially at rpm above say 3k. you probably have a different problem than vvt

 

[SpareParts]

VVT requires a HV oil pump
If VVT is not functioning properly, you will get a few codes, P0011 being one. I also had traction control disabled, Stabilatrac disabled. Hot idle i had the problem with 15PSI.

 

[rdezs]

Keep in mind with a high mileage VVT engine, it provides oil to the VVT actuator through the number two cam bearing. They do that by putting a groove in the bearing that reduces the bearing space by a good percentage, and is probably why the number two bearing is often the first to go in the VVT engines. You might have 20 or 30 PSI at the other bearings, but much less at that bearing if it's blowing oil out the sides.... Which will starve the VVT actuator.

Friend of mine that works in the shop at the local Chevrolet dealer said on the 6.2 L94 AFM/VVT engines, they get five or six every month and all between 195,000 and 210,000 miles.... He calls it predictable. In most cases they waited to change the oil until the display told them to. He said it's always in need of cam bearings, even if it showed up with a collapsed lifter. To help people keep costs down, they strip down the block to change the cam bearings. Replace the rod and main bearings, install new rings on the Pistons and put it together with a new oil pump and timing chain set. If the hone marks are still visible, which is usually the case, they don't touch the cylinder walls.... Which is per GM TSB.

On the L92 and other engines which only have the VVT, it's not very common but it does happen. Something about the AFM aggravates it quite a bit.

The consistency is the number 2 cam bearing and too long of an oil change interval.

They're not allowed to delete the AFM system, so they repair it. This approach is a lot more affordable for people compared to a rebuilt long block.

It's exactly why when my wife passes 300,000 miles on her L94 that has the AFM deleted.... I will have an iron block 6.0 with a decent cam around 425 horsepower to drop right in. They don't get as good fuel mileage but they last forever.

 

[SpareParts]

The 6.2 i have on the stand had a trashed #2 cam bearing. Put the wider CH25 bearings in it.
Cam bearings can be changed without removing the crank/rods.

 

[rdezs]

The 6.2 i have on the stand had a trashed #2 cam bearing. Put the wider CH25 bearings in it.
Cam bearings can be changed without removing the crank/rods.

If you're in that far and it's on the stand, I would go ahead and replace the rod and main bearings as well as the rings.

I do like the VVT for the low end torque, fuel mileage and overall drivability.... I think it just requires oil changes at a more reasonable interval, like 4500 miles maybe. That groove in the VVT camshaft puts all the force on probably 30% less bearing surface.

For overall longitivity, as well as simplicity and strength, I personally lean towards doing a VVT delete.