Million Dollar Spark Plug: Do The Job Right The First Time

Customer with an interesting previous "repair" needs his vehicle to get a second look. Come along with us as we diagnose the issue.

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[NotFastEddie]

The first thing you do to find a single cylinder misfire is NOT a compression test. The first thing you do is swap the coil from the offending cylinder with that from a known good cylinder. If the misfire moves, then the problem is the coil. If it doesn't move, then you pull and inspect the plug and replace if necessary. If the plug is good but it's not firing, then inspect the electrical system for the fault. If the plug is firing as it should, THEN you do a compression test. You got lucky going straight to the compression test THIS time, but this is a rare failure.

Start with the cheapest to fix, simplest to fix, and most likely cause/s first.

[DavidBrown-jtyi]

We just lost a 2021 6.2 motor on a GMC Yukon Denali at 31, 500 miles. They told me it was a Cam Shaft issue and replaced the motor under warranty. The engine made a light ticking sound for about 20 minutes before total failure at low speeds. No light on the dash or codes were ever thrown before it fell apart. Love this channel because I learn a ton.

[moonlite]

It all sounds expensive, but it also gives them comfort, knowing that their vehicle is being cared for by professionals. You guys are absolutely amazing.

[dirtapple]

Hey man, my dad is a master mechanic, and every time I don't have to ask him for help, I just tell him what I did, brings me the pride that I never got as a kid. Thanks for helping me on my journey, this isn't relevant to my current trail, but I'm gonna put it in my hat for later.

[pitpride]

My wallet hurts for these clients. But you guys are honest and thorough.

[alexandre]

"Dont throw parts and stuff, man! Figure out whats wrong!" Preach

[wglnaeclipse]

Dump the oil and inspect it and the oil filter for any metallic bits. If the cam's been worn to the point it won't actuate the lifter there should be metal everywhere. If there's no metal then a collapsed lifter is most likely (thought not 100%) the extent of the issue. The information gathered from inspecting the oil/filter will make choosing one of the three described options a lot easier for the client.

[omnicode]

Yup --- just left a dealership and we dealt with quite a few of these. The mistake a lot of techs are making is not inspecting the engine fully. They recommend only lifters, push rods, and maybe a rocker arm. Meanwhile the cam is wiped out or worse the bottom end has suffered from an oil filter clogged with metal or one that has hit the bypass and ruined the motor completely.

After a while we started letting customers know worst case scenario up front: we may need to replace the motor, warranty or not.

Extra note: right before I quit we replaced a 6.2L that had lifter problems. Customer drove on the blinking CEL. I'm talking severe. I pulled this in and the whole shop was looking at me it was that loud. Bottom end was lost: Gold in oil filter. We replaced the motor with one from GM. Brand new. The thing is banging and clacking after a 20 mile test drive. I pull the oil filter and it looks like someone's kid dumped about 5 lbs of gold glitter into the engine oil. Filter internally looks like something from Alice and wonderland with the gorgeous gold color streaks and I took my TIME pre-lubing this engine.

GM (GMC) had sent us a SECOND bad engine (Sierra 1500): this vehicle had maybe 15k miles max. The customer was out of their rig for over 3 months. Do NOT buy a new vehicle and take care of your old one. We had to replace the replacement motor.

[binger]

Dave,

first I want to say I love the channel. Guys like you and I are dying breed. Being a semi retired factory trained gold master Porsche Tech specializing in diagnostics. I have the same standard that you that you have. One must prove the problem to get to the root cause before you start throwing parts at it. They don’t train these guys properly anymore. They want to plug an OBD scanner, get the codes and change the part without proving the root cause. IE: parts changers.

Love that you are mentoring and training your guys the proper way. Keep up the good work.

[nickbee]

Don’t overthink compression testing. Keep it simple. Use relative compression. If you have one dead hole only like in this video, then crank the engine over in clear flood mode. Use your ears and listen to how it turns over. Does it have a consistent cadence to it? Do you hear an uneven rhythm? You can get an idea of where you need to go next based on what you hear before you even start putting tools on things.

[Sherlock]

What a great shop you run Dave! No BS, just the truth, thats what sets you apart from many others! Thanks for the channel !

[cyclonetransportation]

First thing I do is swap coils and plugs. If no change then compression test unless I hear ticking.

[Ingveyisnthome]

I love the detailed
answer and options ge provides.

[robertschwarz]

AFM Lifter failed- they go bad all the time on GM trucks. Just pull the valve cover off and crank it over, if the rocker arm isn't moving the AFM lifter failed. Sometimes it needs a cam also.

[markhuyette]

I been thru that telling people bad news it's hard to tell someone to bend over because it's going to hurt to fix it right keep up the good work making videos and have a blessed day today 🙏

[aaronlaskowski]

If the camshaft is still ok, and the rest of the engine is deemed ok, check to see if there are any updated parts for the AFM manifold and valve covers, PCV, or just put a catch-can on it.

[alexanderardelean]

I’ve learned so much from this channel being a technician thank you Dave for all your knowledge

[mickwolf]

I like how you try to educate the customer to make an informed decision just like you educate the viewers of your videos.

[pauljanssen]

I remember the day doing all these tune-ups with points and condensers having a lot of fun replacing plug wires and cleaning caps and rotors. It was amazing but a lot of the champion spark plugs that pulled out the the outer electrode was missing. Poor quality control by champion. And they used to be the number one company.

[bb]

Thank you Dave for your excellent videos!