i replaced one collapsed lifter on cylinder 4 . reassembled and now it will idle fine but when i test drive it i get a cylinder 7 misfire and it sounds like a lifter knock. i think it has something to do when the afm kicks in. please help

 

i can rest the codes let it see and start it up it runs like a top it revs great idles great too. but as soon as i go for a test drive it fails again.

 

176 views and no help somebody has to have some input?

 

Have you tried driving with truck in manual( i use M5) to prevent AFM from shutting down cylinders, my 2009 GMC (6 speed auto)has AFM issues and while I try and figure out what to try next, have been trying to drive in M5 around town , that keeps AFM off and motor running on 8 cylinders. Dealership wants $5000 + to "repair lifters and Cam" Truck has 71k miles but warranty over in years so no assistance from GM. Truck is running fine, but has noise around 1500 rpm, barely hear it at idle, using 1 qt oil in 1000 m. Just happened 3 weeks ago.

 

I would also suggest you check the compression to make sure 7 has not failed or is failing..
What year model? you can get a AFM disabling device for around $200, I did this at the first sign of oil consumption and my oil consumption stopped and my oil analysis is coming back looking much better then before the AFM disable...
2007 Tahoe with 109,000

 

thank you for the reply's i think i fixed it for now lol. i ended up replacing all the afm lifters and the vlom. i believe number 7 was starting to fail. i hope this last for another 100k lol

 

Redneckracer01, my buddy has an 07 5.3 LTZ Tahoe. I think he has a collapsed AFM lifter also. It sounds pretty rough at an idle but if I rev it up past 2000 RPM it sounds fine, but once its below 2000 to an idle its ticking again. I'm going to pull the valve covers and start it, see if I can pin point which one it is but I was wondering if I'm going to need any special tools or anything to replace them ALL. I'm planning on inspecting the cam, and using all new gaskets and head bolts going back together thanks