3

I have a 2008 gmc yukon 5.3L that has developed an engine vibration at low speeds with cylinder deactivation like when coming to a stop. Does not vibrate while normal low speed cruising but when stopping. does or has anyone heard of this and if so does GM have a fix for this, I'm talking about G's AMF system.

  • Welcome to Motor Vehicle Maintenance & Repair! Do you have a check engine light lit? If so, have you read the codes? Why do you think it is cylinder deactivation which is causing the issue? – Pᴀᴜʟsᴛᴇʀ2 Mar 3 '18 at 1:56
  • How many miles has the engine done? Have you done any cylinder balance / compression tests? Is there a crankshaft vibration damping pulley? Is it in good condition? – Solar Mike Mar 3 '18 at 6:02
  • Do you get the same vibration if you turn off the cylinder deactivation at low speeds? – Solar Mike Mar 3 '18 at 6:52
0

I had a thought this morning. One of the main things which goes wrong with the cylinder deactivation as GM does it in the LS engines is one or more lifters will go bad very often once there's a few miles on the vehicle. When the lifters start to wear out (I believe there is only a different lifter on the intake side), they will start to lose pressure very easily and will do cylinder deactivation on their own. Later when they are completely worn out, you'll get the problems at pretty much any RPM. This is a very typical issue with the cylinder deactivation as GM implements it.

What could be happening in your case is, as you are slowing down in your Yukon, the oil pressure will start to drop, which will cause the lifter to not be fully pressurized. As you step on the throttle again and start to accelerate, the oil pressure goes back up and the lifter will get back up to its proper "pumped up" height, allowing the intake valve to open as it should.

If this is the problem, in order to fix it, you have to replace the lifters at a minimum on the intake side (it makes sense to replace both, though, since you're already in there). To get to them, the heads have to come off (replacing both lifters and trays), so it's a bit of work.

  • Also doing something about the oil pressure is good - a new pump - a "standard" thing on the Rover (Buick) V8's... – Solar Mike Mar 3 '18 at 16:18
  • @SolarMike - Only if the oil pressure itself is an issue. The LS motors don't usually have this issue. The lifters used in cylinder deactivation are a known issue. – Pᴀᴜʟsᴛᴇʀ2 Mar 3 '18 at 16:26

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.