Help us help you. By posting the year, make, model and engine near the beginning of your help request, followed by the symptoms (no start, high idle, misfire etc.) Along with any prevalent Diagnostic Trouble Codes, aka DTCs, other forum members will be able to help you get to a solution more quickly and easily!
I have a 09 Chevy Avalanche with 5.3 liter with D.O.D engine have a misfire on cyl #4 and slight lifter noise on bank 2. Have checked compression on cyl. #4 and have 180 pounds when cranking I then did a running compression test with scope and a pressure transducer and looked like it was pulling a vac on that cylinder I then hooked up a manual vac gauge and it is showing a pulsing vac. I think I have a bad D.O.D lifter on that cylinder and will need to remove the heads to inspect the lifters is this any thing you guys have ran into?
Hitting it with a Hammer is worth $5 knowing where to hit is worth $40
Hey Ephratah! Definitely sounds like you have a stuck closed intake valve, very likely due to a seized lifter. The only other variables I've run into are cam lobes wiped out by the failed lifter, and leaking VLOM (the solenoid pack in the engine valley that runs the lifters) seals causing lifter failure. I have never seen a VLOM that failed in such a way as to make BOTH lifters on the same cylinder fail.
I'd suggest pulling the bank two valve cover and cranking the engine. If you see one valve stuck closed, then it's either a failed lifter or a completely wiped cam lobe. You're right, head removal will be required to inspect the lifters and cam lobes. If the cam lobes look good, then go for lifters and a VLOM. If you find a wiped lobe, then it may be engine time... These engines also like to burn oil on the DOD cylinders, causing repeat spark plug failure. GM has a TSB they've revised, like, 20 times on this issue. :lol:
I ran into this on a similar year trailblazer with a #6 misfire. It had good compression as well. Running compression showed compression at first and then 0psi there after. We found the lifter had spun in the guide, we ended up replacing all of the lifters and everything associated on that side considering we had to remove the cylinder head! I think your next step is to pull the valve cover and see whats going on visually, then sell the tear down!
Customer has opted to not have the heads removed and is going to look for a different engine. I do not think that they oil changes have been kept up on this vehicle and I am not wanting to open a can of worms here I am afraid that if I pull it down there is going to issues with the cam and DOD solenoids.
Hitting it with a Hammer is worth $5 knowing where to hit is worth $40
Topic Author
These engines are NOT one of GM's better designs, IMO.