No Compression cylinder 7

[BrandonH13]

2007 Yukon 5.3 Flexfuel, AFM with 142xxx miles

So we have had our used Yukon about 2 weeks now and not even 1000 miles. The other day my wife is driving it and calls me to tell me that the service traction control / stabitrax is on and the check engine light is on. Well I take it to Oreilly and have the code read....Misfire cylinder 7 and throttle/pedal position sensor range (p0121). Write them down and clear them. Everything comes back within 2 minutes

So last Friday I bring it to work and read the codes again. Now just getting cylinder 7 misfire. So I take out the spark plug and its covered in sludge.....great. So I go ahead and check the rest. Doesn't look like they have been changed ever and number 4 the porcelain was broken, so I run down and grab 2 plugs and put them in thinking it was the fouled plug. Nope, code comes back so I switch wires and coil to no luck. Then I start to notice there is a clack clack clack at idle, so I call our local chevy dealer. I took it to them yesterday and they came back with the number 7 cylinder has no compression.

So they said it would be another 2 hour shop rate to actually tear the engine down and see what exactly is wrong. I am guessing that since it has afm and it has 142xxx miles that the lifters collapsed on me. This is just SUPER frustrating since we literally just bought it and its in the shop for a expensive repair. So now I guess my only option is to try to contact GM and see if they can help me out, but I doubt it since I am the 2nd or 3rd owner and just bought the vehicle.

Anyone else have this issue, I have seen people turning the AFM off with black bear, but I don't have an extra couple hundred dollars to throw at a custom tune for something I just bought. I thought about doing the oil catch can and seeing if that helps out with it. Most of the time we drive highway so its always kicking in and out of AFM

 

[Atomic]

Take off the valve cover and see if one of the rockers is loose or wobbly for that cylinder. However, since the shop said it had no compression that is either a piston/ring failure, or a valve failure. I would do a leak down test before you take the head off, that way you can at least narrow it down to a top end (valve) or bottom end (piston/ring) problem.

 

[BrandonH13]

Well its at the shop and if I can get it half way covered I will have them do the work. The dealer we bought it from "SOUNDS" like they will honor their 50/50 warranty as I called them yesterday and told them what was going on and said it could be rings/piston, lifters, or if bad enough need a new engine. He was shocked but said that their mechanic they use didn't need to look at it and to keep him updated on what was going on with it.

 

[BRUTUS_T_HOG]

The valve cover will need to be removed and see if one or both of the valves are not moving in that cylinder. It is likely bad lifters or a flat cam.

Huge job to replace lifters the head has to be removed

 

[nick2440]

Im not very familiar with the 5.3 but im sure it has valve springs and maybe one of them broke and is dropping a valve and hitting the piston each revolution? Curious to hear the outcome

 

[BrandonH13]

We got the Yukon back on friday. It was the lifters and they replaced 4 and the left manifold. All together it was a $2200 job

 

[Atomic]

Wow...I wouldve done it for half that and still felt like I was ripping you off. :/

 

[BrandonH13]

Lucky for us, we have an aftermarket warranty that took care of a little over $1900. They just didn't pay for the fluids (oil and coolant) and the sales tax. We owed about $244 and then the dealer we bought it from is suppose to reimbuse us half since it was still under the 30 day warranty with them.

 

[Atomic]

Not too bad then!

 

[BrandonH13]

Not at all, I would of done it myself if it wasn't covered. Would of just been worried about taking the head off would of been the only thing