Girlfriends 09 Yukon with a 80k mile 5.3L threw a P0302 code. It has a VERY small miss at idle when its in gear, you almost can't even feel it. When its at idle in park you can't even really feel it sitting inside the truck, but if you watch the motor you can see it shaking just a bit because of the miss. Truck drives down the road great is whats odd. Its not like a full dead miss. Anyhow so I figured it may be a coil pack so I swapped them and the issue is still there on #2. The spark plug looks good and I can tell its been firing. Changed the plug anyways to see and still does it. If you bring the RPMs up to about 1500 rpms and hold it you can hear a small ticking noise on #2 that the other 7 cylinders don't do so I went ahead an pulled the passenger valve cover, everything looks good and when I spin the motor over everything is working at it should. I ran a compression test on all 8 and #2 is about 35 psi lower then the rest.. Truck doesn't use any oil, runs great other then that small miss that just started. Anyone got any ideas? Starting to wonder if its starting to develop a lifter, cam lobe or some other issue..

 

I hate to break it to you but it sounds (from what youre describing) like the beginning signs of a wiped or spun lifter....as far as the lower compression on 2 need to do some more digging on that, but a sticking valve or weak valve spring could cause that as well as the misfire...

 

That is what I was thinking as well unfortunately. I just wanted to get some input before I tore off into it. Should I go log fuel pressure, kill injectors etc and all the other tests to see if anything stands out or are you pretty sure that is my issue? If indeed it is Ill just do a DOD delete and a LS2 cam, ls6 springs and get it tuned.

 

Compression and leakdown test probably be more prudent and revealing than the others....may be a lifter stuck in bore or a valve sticking in guide causing low compression as well as a ring issue, rarely see head gasket issues on these.... Which 5.3 is it the aluminum or cast iron block???

 

If youre gonna delete dod save yourself some money and put the kit together yourself, i can get you part numbers that will save you money over a put together delete kit, 4.8/6.0 non dod truck valley cover is a third the price of the ls3 cover, youll need lifters and trays, head bolts, head gaskets, waterpump, timing cover, valve cover gaskets and the orings for the colant crossover tube....

 

It's a cast iron block.. part numbers would be great! I guess right now I'm trying to decide if I should just go ahead and tear into it and see if the issue shows its face or keep further diagnosing. I'll probably do the leak down. If that doesn't show anything I guess I'll tear into it.

 

Ill post part numbers/retail prices tonight when i get home... Only few i dont have but are readily available with a minimal search...

 

12595365-lifter trays(x4)
12598832-valley cover(truck version without pcv port) $45
12617944-exhaust manifold gaskets
12589226- head gaskets (5.3) $38.51(x2)
12637683-valve cover gaskets (x2) $22.89
19258707-head bolts (11-1.5)(x20) $1.18
12558840-head bolts (8x1.25)(x10) $2.16
12630223-water pump gaskets(x2) $6.66
12588670-ls2 chain dampener $20.21
12633904-timing cover gasket $27.14
12557840-crank bolt $5.79
12589016-cam retainer plate $24.50
Exhaust manifold bolts.... Forgot to get pn before i left work today
I dont have the part number available at the moment for the factory gm lifters, and there are a few other miscellaneous seals its a good idea to replace (i.e. Crossover tube orings, intake gaskets, if you end up having to pull the oil pump the oring for the pickup tube) i have replaced the tesnsioners on the 5.3/6.0 engines by unbolting the oil pump and GENTLY prying it out just far enough to get the bolt on the driver side of the tensioner out, which i dont necesarily recommend anyone else do.... It is a very scary process, but beats the hassle of dropping the oil pan.... If you decide to reuse the tensioner, heat it with a heat gun and gently pry it back and put a paper clip or something in the hole to hold it (i have a collection of tensioner "grenade" retainer pins i use...) you will also need a cam and if its a 3bolg style a 4x3 bolt cam gear....
Edit--- all prices are dealer list....

 

Fel pro head bolt kit is $45 per head..... Ill go with gm for less for both heads!!!!

 

Look at this thread for some part numbers your missing ---> https://www.performancetrucks.net/fo...umbers-428941/