Failing lifter?

[bcbickers]

Greetings All,

My new-to-me 2012 Suburban Z-71 started idling rough and missing this past weekend. With 151k on the clock and the last tune-up done at 75k, I figured it was time for a tune up and swapped in new AC Delco plugs and wires. The hiccup/miss actually got a bit worse and eventually threw a P0306. I thought maybe a bad wire, so I swapped the plug wires between #4 and #6, reset the codes, and drove around. No new codes after 50 or so miles and a 15 minute idle session in the driveway, but now I hear what I think is a lifter tick. It seems to run fine and make no noise or stumble when cold or at speed (oil pressure above 40 psi) but shudders/misses at lower speeds. Do I have a failed or failing lifter? See video.

 

[bcbickers]

Just realized I was in the Performance forum and not the Engine forum. Was researching fixing the 5.3 vs swapping in an L96 or LS3 just in case.

Mods, please move if needed. Thanks, and my apologies again for posting in the wrong forum.

 

[iamdub]

Greetings All,

My new-to-me 2012 Suburban Z-71 started idling rough and missing this past weekend. With 151k on the clock and the last tune-up done at 75k, I figured it was time for a tune up and swapped in new AC Delco plugs and wires. The hiccup/miss actually got a bit worse and eventually threw a P0306. I thought maybe a bad wire, so I swapped the plug wires between #4 and #6, reset the codes, and drove around. No new codes after 50 or so miles and a 15 minute idle session in the driveway, but now I hear what I think is a lifter tick. It seems to run fine and make no noise or stumble when cold or at speed (oil pressure above 40 psi) but shudders/misses at lower speeds. Do I have a failed or failing lifter? See video.

It could just be the camera mic, but it doesn't sound like a lifter to me. Sounds more like an intermittent spark arcing. Are you sure the wires are fully snapped into place? Are you sure the plugs and wires you installed are truly AC Delco? Are they AC Delco OE, Professional, Advantage, GM Genuine, Gold or Silver? Where did you get them?

 

[Miami-Dade]

@bcbickers Moved thread over here. You will get more help here.

 

[tom3]

Loose plug?

 

[bcbickers]

It could just be the camera mic, but it doesn't sound like a lifter to me. Sounds more like an intermittent spark arcing. Are you sure the wires are fully snapped into place? Are you sure the plugs and wires you installed are truly AC Delco? Are they AC Delco OE, Professional, Advantage, GM Genuine, Gold or Silver? Where did you get them?

AC Delco OE, I think. Wires are 748UU, and plugs are 41162 gapped at .040 (checked with a tool). All bought them from Rock Auto. I did a run through after swapping everything in, but I can certainly recheck everything. And that is exactly what it feels like: spark being blown out every so often or maybe a bad wire. I'll pull everything again and triple-check.

 

[Trey Hardy]

AC Delco OE, I think. Wires are 748UU, and plugs are 41162 gapped at .040 (checked with a tool). All bought them from Rock Auto. I did a run through after swapping everything in, but I can certainly recheck everything. And that is exactly what it feels like: spark being blown out every so often or maybe a bad wire. I'll pull everything again and triple-check.

What gas do you run in it? I know I thought I had a rod knock for awhile before a old mechanic asked me if I ran that “cheap gas” he said to throw some B12 or marvel mystery oil in the gas if I run the cheap stuff to prevent spark knock…
I also had a lifter stick I used a quart of marvel and 10w40 synthetic oil to help get it “free” and I’ve been doing this for about 100,000 miles almost now with good luck.
This is just a bandaid obviously
My lifter tap sounded far worse then the video you posted

 

[Trey Hardy]

Sounds like spark knock to me but I could be wrong.

 

[iamdub]

AC Delco OE, I think. Wires are 748UU, and plugs are 41162 gapped at .040 (checked with a tool). All bought them from Rock Auto. I did a run through after swapping everything in, but I can certainly recheck everything. And that is exactly what it feels like: spark being blown out every so often or maybe a bad wire. I'll pull everything again and triple-check.

RA should (still) be a reliable source for genuine parts, so you should be good there. Good on you for confirming the gap. The LS wires, with that heat shield, can be tricky to know if they're fully clicked into place. It'd be an easy item to check. I hold them by the rubber boot and twist them at least one full turn while pushing in to ensure they're fully seated, then I plug in the coil side.

Trey's comment on spark knock is a good suggestion. Did you get gas right before this all started? Maybe that station had bad fuel. I'd try his suggestion or maybe some octane booster. Maybe top off with some premium if you've burned any considerable amount out of that tank.

 

[bcbickers]

RA should (still) be a reliable source for genuine parts, so you should be good there. Good on you for confirming the gap. The LS wires, with that heat shield, can be tricky to know if they're fully clicked into place. It'd be an easy item to check. I hold them by the rubber boot and twist them at least one full turn while pushing in to ensure they're fully seated, then I plug in the coil side.

The wires I got from Rock Auto don't have the metal shields and springs. They are just a standard rubber boot. See the pic below. I will definitely recheck all of the plugs and wires this afternoon. Worth the effort before I rebuild the engine.

Trey's comment on spark knock is a good suggestion. Did you get gas right before this all started? Maybe that station had bad fuel. I'd try his suggestion or maybe some octane booster. Maybe top off with some premium if you've burned any considerable amount out of that tank.

I don't think it is gas related because I filled up at a couple of different locations in different cities this past weekend. I drove to my family's ranch on Saturday (350 mile round trip), and it started acting up on that trip. Gas mileage was 14 mpg mostly 90% freeway running 70-75 mph.