[phonzy]

Hello friends, I'm new here and this is my first post.

I literally made this account to get some insight and hopefully some help for myself and my journeyman mechanic friend on my PITA truck. My truck is a 2006 Sierra 1500 SLT 5.3L "T" engine with a nice list of mild upgrades.
I recently just did Spark plugs (NGK) Spark plug wires (NGK) new GM knock sensors, GM intake manifold gaskets. Now the long story short... I was out elk hunting... Truck went into limp mode in a snow infested field (I live in Saskatchewan, Canada) in literally the middle of no were. Had to get my buddy to tow me, my trailer, quad, and elk out. Had the truck flat decked to a mechanic shop that tried to fix it (they did an O2 sensor, new plugs, new wires. They were a bunch of brain dead idiots to say the least. **So to get to the point the truck had a nasty misfire that they said cleaned up with a tune up. Truck drove good. Only issue was when cold, it would shake and shutter a bit. But when warmed up it would run like a top. Had the knock sensors done at my buddies shop. Truck still shuttered. Took it back and we looked at it. Took the intake manifold off checked to see if it was warped or not... It was with in spec. Changed out to the new updated GM intake manifold gaskets. Put it all together and it still shuttered and idled goofy when cold. We tested everything... fuel pressure, compression, swapped injectors, swapped coil packs ... Put a misfire counter on #8 and its misfiring when cold, but clears up when warm (none of the swaps changed anything) We did a leak down test. DING! #8 lifter is collapsed YES! well... lets double check it to make sure... Well it passed no collapsed lifter...
What in sweet baby zombie jesus's name is going on? Please help... Will send elk meat... and beer... and a hardy hand shake!
(ps... sorry for the ramble thats probably mixed up)

 

[esox07]

Just a guess but it sounds like you might have an vacuum leak. It could be around the intake or a vacuum line. I would try a thorough leak test. It is a lot cheaper than throwing parts at it. Just make sure to do the test when the motor is cold.
Let me know if I win and I will send you an address to ship the Elk Steaks.

 

[apcnc]

Did you hear a lifter? Watch the vacuum through the diagnostic port. Could also be carbon on the valve, Seals. Check the plug when cold. Clean oily etc. Spray some water through it to clear any carbon buildup. Have you done a paper test on the exhaust?

 

[phonzy]

Just a guess but it sounds like you might have an vacuum leak. It could be around the intake or a vacuum line. I would try a thorough leak test. It is a lot cheaper than throwing parts at it. Just make sure to do the test when the motor is cold.
Let me know if I win and I will send you an address to ship the Elk Steaks.

We've looked and checked around the intake manifold, its been off twice and all vacuum lines looked over. I've noticed on my AFE intake the bellows are slightly cracked... Not all the way through but goinng to change them out and clean the MAF sensor as well. Where else could we look for a vacuum leak? Any known lines to let go?

 

[phonzy]

Did you hear a lifter? Watch the vacuum through the diagnostic port. Could also be carbon on the valve, Seals. Check the plug when cold. Clean oily etc. Spray some water through it to clear any carbon buildup. Have you done a paper test on the exhaust?

Can't hear any lifter click. Just put in some Forte pre-lube (http://fortesystems.ca/products/pre-lube-service/) We also did some sea-foam purging into the manifold. No paper tests to my knowledge. Just watched it on a fancy monitor.

 

[djlove]

Spark plugs (NGK) may be a new issue. These motors typically get finicky if you dont use delco iridiums. You could also check the gap on the #8 cylinder, i had a set of plugs where the parts guy told me these are the plugs i needed, installed, 5.3 ran like garbage. I took them back to the store and they pulled up more info and sure enough they were not the correct gap and not even the right plug listed in the parts chart.

The original problem you mentioned though sounds alot like the throttle position sensor issue that alot of the early 00's had. You can now order online just the TPS if your handy with a drill. Some kits come with a new throttle body gasket which wouldn't be a bad parts cannon projectile to throw at it. Two bottles of chevron techron are what i run through both trucks twice a year and it helps smooth the engine out as well.

http://www.ebay.com/itm/NEW-Dorman-977- ... sF&vxp=mtr

 

[phonzy]

Spark plugs (NGK) may be a new issue. These motors typically get finicky if you dont use delco iridiums. You could also check the gap on the #8 cylinder, i had a set of plugs where the parts guy told me these are the plugs i needed, installed, 5.3 ran like garbage. I took them back to the store and they pulled up more info and sure enough they were not the correct gap and not even the right plug listed in the parts chart.

The original problem you mentioned though sounds alot like the throttle position sensor issue that alot of the early 00's had. You can now order online just the TPS if your handy with a drill. Some kits come with a new throttle body gasket which wouldn't be a bad parts cannon projectile to throw at it. Two bottles of chevron techron are what i run through both trucks twice a year and it helps smooth the engine out as well.

http://www.ebay.com/itm/NEW-Dorman-977- ... AAAOSwV0RX

The plugs were all gaped to spec. The idle is only erratic at the initial start up along with the misfire. When the vehicle is warm, absolutely no issues.

 

[apcnc]

The AC Delco's are NGK unless that's changed. Still could be the wrong plug but Id check it and make sure its the same plug before replacing. Also Have you switched the plug out with another one. Checked the harness/connections to the coil pack? Did you change the plugs after this happened or before?

Did you ever see any contamination on the plug, oil coolant etc?
paper test: Just take a piece of paper and hold it to the tailpipe. If it blows out that's good if it flutters back and for a valve/s isn't closing.

 

[phonzy]

The AC Delco's are NGK unless that's changed. Still could be the wrong plug but Id check it and make sure its the same plug before replacing. Also Have you switched the plug out with another one. Checked the harness/connections to the coil pack? Did you change the plugs after this happened or before?

Did you ever see any contamination on the plug, oil coolant etc?
paper test: Just take a piece of paper and hold it to the tailpipe. If it blows out that's good if it flutters back and for a valve/s isn't closing.

I had the exact same plugs in it before the issues. I've changed sets of wires to better NGK ones (clowns used some cheap crappy ones) Swapped coil packs and no changes. As for the Paper test i can give that a whirl!