2009 Chevy 5.3 w/AFM delete cylinders 3 &5 misfire

[James William Hill]

I have a 2009 Chevy 5.3 that has random misfires on cylinders 3 & 5 but no CEL. I did full afm delete using a texas speed kit. The only parts that were not gm are the lifters everywhere I looked they were on back order and I needed the truck back on the road quick. The cam is a stock GM single bolt cam nothing special. Everything was thoroughly cleaned during reassembly, and assembly line was used. Also I followed all torque specs . Also the afm was deleted out, and the TPS, cam shaft sensor and crank shaft sensor were all reset. The only issue during reassembly was the the cam gear jumped off the dowel pin and I didn't not know until the first crank that it was out of time and was back firing through the intake. After that was fixed it ran like a champ. Within a couple weeks of it being back on the road I noticed it had a rough idle and the rpms would bounce up and down. The rpms dont drop low only up and then back to "normal", and there is no CEL on. I had someone with a matco scanner scan the engine. It showed random misfires on cylinders 2, 3, 5 and 7. I was told all fuel trims also looked normal. I have cleaned the MAF sensor, changed the plugs and wires using ac delco plugs and wires. The rough idle is still there I have not had rescanned but I can only assume the misfire is still there and no CEL. The original plugs (pictured below) were as delco 41-110 with only 60k miles on them I went back with ac delco 41-162. Also all coils and injectors are still orginal. What could be the issue?

 

[Doug_Scott]

Maybe its just me, but the two plugs at the left end of the line look like they are covered in black carbon.  The last plug looks like it is missing its tip.  Try checking for a vacuum leak on the left side of the intake, assuming the engine is configured like the standard small block, odd number cylinders were on the left bank.  

[Jsdirt]

I thought that same thing about the ones on the right end, Doug, at first glance - just an optical illusion.

 

 

I would be pulling the valve covers and measuring pushrod / rocker arm travel, followed, or preceded by a compression and leak down test. I'd probably do the comp/leakdown first to save myself the trouble of yanking the covers if that checks out ok. Could be anything from a mechanical issue, to clogged injectors, or an electrical problem - pinched wires, or forgotten grounds after an engine job are very common.

 

None of those cylinders is an AFM cylinder except for 7, so unless the computer is flagging the wrong cylinders, that rules out the wrong cam or lifters, I believe. Do a Google search for the brand of lifters you bought to make sure they're not duds. I'd get on the horn with Texas Speed for some guidance, after you do some troubleshooting. Don't forget to come back here and let us all know what the problem was as well.

 

Nothing wrong with using proven aftermarket components in a AFM delete. These engines have been around long enough now to know the winners and losers. Why buy GM components when they couldn't build the engine correctly to start with? That's my line of thinking here. That's why when my rear differential wore out and my spider gears shed all their teeth at 97k miles, I installed an OX air locker. The GM replacement would've been much cheaper, but I don't feel like doing the job again in another 90k miles. Those parts have proven to be low-bidder junk.

 

 

EDIT: Forgot to ask the million dollar question: Who did the engine tune after the AFM delete?