'07 5.3L V8 to V4 switching has slight vibe

In V8 mode the engine runs smooth but as soon as it switches to V4 I get a noticeable vibe, the same kind of vibe when an engine is missing, and that slightly different sound that sounds like a miss. It never stays in V4 at steady speeds, instead quickly switches back to V8 because V4 can't hold speed. All this and the fact my mileage sucks makes me think I'm down a cylinder. Everyone else says their switching goes unnoticed whereas I can hear and feel mine. Is there a simple way I can check if I have cylinders missing or even pinpoint which ones? Does the V4 operation always use the same cylinders? I've hooked up OBD and that says nothing. Maybe need a better one? Thanks

In V8 mode the engine runs smooth but as soon as it switches to V4 I get a noticeable vibe, the same kind of vibe when an engine is missing, and that slightly different sound that sounds like a miss. It never stays in V4 at steady speeds, instead quickly switches back to V8 because V4 can't hold speed. All this and the fact my mileage sucks makes me think I'm down a cylinder. Everyone else says their switching goes unnoticed whereas I can hear and feel mine. Is there a simple way I can check if I have cylinders missing or even pinpoint which ones? Does the V4 operation always use the same cylinders? I've hooked up OBD and that says nothing. Maybe need a better one? Thanks

this system uses the same 4 cylinders to operate in 4 cylinder mode. at 60 mph level road , steady throttle the engine should stay in 4 cyl mode.

I suspect that the lifter control of the cylinder valves are defective on those cylinders that cut out in this 4 cyl operation.

excessive oil consumption has been observed after 60,ooomi with this DOD..

with the standard 4 speed tranny this is a poorly designed power train DOD system. the use of a CVT type tranny would provide the best load with an engine of this ability.

the newest GM experiment with this type of MPG gaining vehicle uses what they call a EVT tranny in the hybrid vehicles made.

I don't see how the dealership has the ability to repair that EVT..must be a total repalcement job.

if things are working correctly you should get 15 mpg ...ave. hywy only at 60 mph 20 mpg. you go too fast no 4cyl mode lower MPG !

this system uses the same 4 cylinders to operate in 4 cylinder mode. at 60 mph level road , steady throttle the engine should stay in 4 cyl mode.

I suspect that the lifter control of the cylinder valves are defective on those cylinders that cut out in this 4 cyl operation.

excessive oil consumption has been observed after 60,ooomi with this DOD..

with the standard 4 speed tranny this is a poorly designed power train DOD system. the use of a CVT type tranny would provide the best load with an engine of this ability.

the newest GM experiment with this type of MPG gaining vehicle uses what they call a EVT tranny in the hybrid vehicles made.

I don't see how the dealership has the ability to repair that EVT..must be a total repalcement job.

if things are working correctly you should get 15 mpg ...ave. hywy only at 60 mph 20 mpg. you go too fast no 4cyl mode lower MPG !

That's what I thought...it SHOULD stay in V4 but doesn't. The only time I've seen it stay in V4 for more than 10-15 seconds at 55mph was with a 30-40mph tailwind. I have had mysterious oil consumption as well. Not a dramatic amount, but enough to be abnormal when there are no signs of leaks.
So what can I do to fix this? Replace the lifter control? Is that a DIY job or something definitely left to a seasoned mechanic? I'm totally ignorant on this kind of fancy stuff. Thanks

That's what I thought...it SHOULD stay in V4 but doesn't. The only time I've seen it stay in V4 for more than 10-15 seconds at 55mph was with a 30-40mph tailwind. I have had mysterious oil consumption as well. Not a dramatic amount, but enough to be abnormal when there are no signs of leaks.
So what can I do to fix this? Replace the lifter control? Is that a DIY job or something definitely left to a seasoned mechanic? I'm totally ignorant on this kind of fancy stuff. Thanks

I am by no means an expert with this type of engine. DIY on this would be very hard to do since it must use top secret GM circuits.

I found what I posted here from owners with issues on this vehicle.

I believe you can get a programer for the pcm/computer that will kill the 4 cyl mode ...

I will see if there is one.

the oil use was 1qt every 2,ooomi. some more , some less..

I think I found the disable of the DOD with your vehicle look here http://shop.diablosportpower.com/DiabloSport-Predator-U7194-2006-2012-GM-Car-Truck-SUV-U7194.htm
DiabloSport Predator (U7194) 2006-2012 GM Car, Truck, SUV.


Its 265.oo ...If your out of warrantee the dealership will charge more to look at it.

contact these people I am sure they can give lots of info. also they have a tuning forum. I was going to buy one of these so I could read the ABS codes.

go here also http://www.diablosport.com/index.php?name=PNphpBB2&file=index forum is in here.

found this for instructions to disable DOD http://www.diablosport.com/index.php?name=PNphpBB2&file=viewtopic&t=30005&highlight=dod+disable

My 2007 did the same vibration and I've found the gas I buy is the factor. I generally buy grocery store gas and if from my Costco it does this from another chain it doesn't. I think the vibration is preignition. A GM engineer told me it takes 140 horse power to maintain speed at 60 mph. So in V4 mode it's running at pretty much peak power so it won't take much to drop it out of V4 mode. I've also found it stays in V4 mode better if run in trailer mode or run on mid grade or premium gas. Problem is the V4 mode doesn't save enough to pay for the more expensive gas. I also have the oil consumption issue, 1 quart between 1,000 and 2,000 miles which isn't defined as excessive.

I'm thinking of getting a programmer that will allow me to bump up the shift points on the transmission and see if that helps the V4 mode.

Here's the tell-tale story though the Tahoe hybrid has the 6.0 since it stays in V4 mode better than the 5.3. I suspect if a person did the crank swap necessary to make a 5.3 a 5.7 they'd see better mileage. Or an axle gear swap 4.11 or 4.53. Expensive mods though for a few mpg so I haven't tried it.

[quote=MarkInKeizer;6983680]My 2007 did the same vibration and I've found the gas I buy is the factor. I generally buy grocery store gas and if from my Costco it does this from another chain it doesn't. I think the vibration is preignition. A GM engineer told me it takes 140 horse power to maintain speed at 60 mph. So in V4 mode it's running at pretty much peak power so it won't take much to drop it out of V4 mode. I've also found it stays in V4 mode better if run in trailer mode or run on mid grade or premium gas. Problem is the V4 mode doesn't save enough to pay for the more expensive gas. I also have the oil consumption issue, 1 quart between 1,000 and 2,000 miles which isn't defined as excessive.

I'm thinking of getting a programmer that will allow me to bump up the shift points on the transmission and see if that helps the V4 mode.
quote]

thanks for your experience with these vehicle issues.

oil useage is the norm after 30-40,ooomi. those that killed the DOD have better performance.

Update....after replacing pads and rotors I found on both front left and right rear that one pad was like new and the other was completely gone. My guess is the caliper pins were somewhat stuck, causing brakes to drag(although I never noticed any rotor being excessively hot). Anyhow, my '07 now switches to V4 and will stay there, albeit with the light vibe.

Update....after replacing pads and rotors I found on both front left and right rear that one pad was like new and the other was completely gone. My guess is the caliper pins were somewhat stuck, causing brakes to drag(although I never noticed any rotor being excessively hot). Anyhow, my '07 now switches to V4 and will stay there, albeit with the light vibe.

with my 2000 sil I had stuck pins, distorted caliper pistons, also from factory pads backing plate too large binding up the whole brake in the rear. no problem now replaced all that crap with new lifetime warrantee parts..including the defective park brake .

switching v8- v4 you will get that as the torque is changing.