Misfire Cylinder 1

HJackson

New Member
New poster here, thanks for all you do
5.3 LH6 engine misfire in cylinder 1 no nother codes. Compression 80 - 90. Mechanic indicates Wet compression test indicates no ring damage but it is unclear because each compression test on that cylinder yields different pressures. I'm thinking a loose or damaged lifter. I am not in a position to fix it now. Can I unplug the fuel injector and coil pack and run it until I can fix it? Or do I need to UBER it to work. My thought is that if fuel is sprayed into cylinder and does not burn, raw gas will be exhausted thru cat and may seep down the cylinder walls ruining the viscosity of oil. I've driven it less than 100 miles since the misfire started and anticpate less than 2-300 more. If I go that route, I've seen a video that states cylinder six would cancel cylinder 1 out, so should I unplug that cylinder as well? Any thoughts would be appreciated.
 

MRRSM

Lifetime VIP Supporter
Welcome to GMT Nation...

Your careful consideration of doing possible damage to the CAT with almost Pure Fuel getting dumped inside does you credit. FWIW... On the Outside Chance that some Durable Piece of Carbon or a Carbon Ring of that Stuff has accumulated around the Valve Seats limiting the chance for them to seat and SEAL properly... Try using a Can of ACDelco Top Engine Cleaner.

After Pulling the Spark Plug out of a COOL Engine Head, Spray this Stuff liberally (DIRECTLY) inside of the Cylinder, let this Magical Stuff stay in the Engine and sit in there for a few hours. Re-Apply to get full solvent exposure to ALL of the Valve surfaces up inside the Engine Head.

Before Starting the Engine...USE CAUTION...

Pull the Fuel Pump Relay and with the Spark Plug Hole VACANT... turn the motor over for 10-15 seconds to be certain to remove any Pure Liquid ACDelco TEC that might cause the Motor to Hydro-Lock (think Bent Con-Rods Here...) and make matters worse if you were to put the Spark Plug back into the Engine Head Prematurely.

Then to just to make sure, Aerate that Cylinder with the Red Plastic Nozzle inserted deep into the Spark Plug Hole and using some "Canned Air" before you re-Install the Spark Plug and Tighten it back down to 18 Ft Lbs of Torque. Wear Eye Protection and Nitrile Gloves... THIS Powerful Stuff can HURT You!

Finally... Start the Engine and let it idle for a while. It MAY STILL misfire for a bit... but it might also ease up after you Clear your Engine Codes and and then take the Vehicle for a Short Test Drive around the Block. Don't Over-Rev the Engine on the outside chance that OTHER Mechanical Problems are involved. Let us know what happens after this 'innocuous experiment'.

Here is where to get this FOAMING stuff...


ACDELCOFOAMINGTEC.jpg

A Great Alternative if you cannot find the ACDelco Foam is Berryman's B-12 Carburetor Cleaner in the Spray Can. It will NOT be the Foaming stuff... but it is equally powerful as a Carbon-Busting Solvent. Please ...Do NOT Spray this stuff through the Intake Manifold!
 
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TollKeeper

Well-Known Member
@MRRSM - Agreed... Isnt his a DOD engine? and couldnt that also be the problem?

(Not sure we needed 2 thread for this question thou)
 

MRRSM

Lifetime VIP Supporter
Roger That, @TollKeeper...the GM AFM (Active Fuel Management) variant became available in 2005 in the GMT-360s ...and quite frankly... I would ALSO try to use this Berryman's B-12 Solvent Technique as covered by Brian from his "Briansmobile" YT Channel as a "Last Chance Effort" to loosen up the complicated and likely Gummed Up Innards of the Lifters in that involved Cylinder.

HOWEVER... Depending upon the Vehicle Mileage and Maintenance Service Scheduled attention to the OP's Engine, if the DOD (AFM) Problem is of A MECHANICAL ORIGIN... then using Brian's "loosening up" Technique employing the Berryman's B-12 Direct Spray Treatment will probably NOT work. Nonetheless ...I would STILL give this idea of his a Shot.

Time and again, @Mooseman has suggested investing in the DOD-Delete approach to permanently eliminate this problem and relieve the Owners-Drivers from further worry about NOT IF ... But WHEN Will THIS Problem Rear its Ugly Head?

Here is Brian's Video on trying to solve these Valve Train and Lifter Woes:

 
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HJackson

New Member
Thanks for your replies. I inadvertently posted twice and could not find out how to delete the second post. Still finding my way around the site. I've had the idea of dumping something directly in to the cylinder to disolve/remove carbon deposits so the foam suggested answers that question. Unfortunately, I won't be able to try that until Sunday. In my travels, I did find some videos about the DoD, so you've validated that as well. I don't hear any valve/lifter noise and only suspect the lifter as it may explain the irratic compression test results. In the video I saw, the valve "sleeve" was rotating a full 360 degrees. I still have the question about disconnecting the cylinder. I did find out how to determine if an engine has DOD. The RPO codes are as follows and come from a post dated 11/2017. The label of the codes is in the glove compartment. Some one may want to sticky it. TY All
GM/Chevy Engines Factory-Equipped with AFM
Engine Displacement RPO Code
5.3L LY5 LC9 LH6 LMG LS4
6.0L L76 L77 LFA LZ1
6.2L L94 L99
 

Mooseman

Moderator
Is there a ticking noise around there in the valve cover? If so, it's likely a stuck lifter. There are fixes available but running it like this will destroy your cam and lifter and send shrapnel throughout the engine. If it hasn't been running too long, it can be saved by using this method:

 
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HJackson

New Member
Mooseman, Thank you. In one of his videos, he shows a lifter sleeve(?) rotating 360 degrees. As soon as I saw him rotate that lifter, I had an automotive epiphany. Logically, what else could cause the compression readings to change with every test? Even though I hear no noise from the lifters, I'm confident it is a lifter issue. And optimistic that I can fix it. You have driven it home to park it til fixed and I thank you for that
 

TollKeeper

Well-Known Member
If it is the AFM/DOD issue, there are temporary fixes and permanent fixes. You can do a temp fix, but it can come back, and come back worse than before. Its an oil pressure based system, and pressure will always find the path of least resistance. The ring block with Valley cover modification, with a tune is the cheapest fix, and i do know people that have done it, and have been problem free for years. I personally don't like this fix, but i also haven't done it. The 2 proper fixes is to either delete the system and tune it out, which is expensive, which means the problem never comes back, or to replace the system, which is also expensive, and does not guarantee the problem won't come back, and likely will after some time.

Definitely need to verify the problem, and if i remember correctly, that involves taking the valve cover off, and checking for looseness of the retainers at the valve, spring, and rocker. At that point you can try the DOD/AFM hack, and see if that brings the tension back to the spring, rocker, and retainer. If it does than checking the compression to see if it brought back the compression of the other cylinders of the engine (within 10%).

Whatever you pick, it's a lot of work, but with it in the long haul.
 

MRRSM

Lifetime VIP Supporter
This is an Instructional Video produced by ACDelco showing How and Why the GM AFM (DOD) Lifter Innards get FUBAR'd. The Bird's Eye View of the Inner Plenum is also helpful to see before you decide whether or not to Tackle The Job of installing the DOD Delete Kit:


THIS Dude shows How To Perform all the Serious Work involved on an AFM-DOD Delete:

 
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