‘07 Yukon 5.3L misfires in cyl. #s 2 & 7

[jcb2]

My ‘07 Yukon suddenly shows misfires in #7. And cylinder #2 shows about a third as much misfires. First I threw parts at it(plugs and coils) with no difference. That was just a stupid waste of money. Then I replaced the oil pressure sensor and the infamous oil screen below it. I’ve done this several times over the years and that little screen always has crud in it. It’s the Achilies heel of this AFM system.

Although I keep my oil changed often and the pressure gauge showed high, I thought that perhaps there was a problem not getting enough oil to the Valve lifter manifold. I then bought four quarts of oil flush and four 5-quart jugs of Castro’s GTX long mileage oil. I flushed the engine four times then added new oil and filter.
It ran rough and gave me trouble starting at first. Now it runs only slightly rough and codes are still showing the same misses but only about once a minute. I was hoping it was just a crud in the oil issue. I’m facing the reality that the lifters are sticking and may need replacing. I have 190K in this engine and the body’s showing a hint of cancer in spots so my vehicle’s value at this point is so low that it wouldn’t justify buying all the necessary parts.

I hate to retire it because in the last year I put new tires, brakes, battery, oil level sensor. Also I dropped the oil pan and cleaned it out really well. Other than the misfires, it’s still a good vehicle with 125 compression in all cylinders.

My son wants me to give it one more chance by replacing the oil with ATF and running it for only a thousand miles. He has more experience than me and said that it will clean out any crud without hurting anything.

Has any one tried this? What would you recommend?

 

[jcb2]

My ‘07 Yukon suddenly shows misfires in #7. And cylinder #2 shows about a third as much misfires. First I threw parts at it(plugs and coils) with no difference. That was just a stupid waste of money. Then I replaced the oil pressure sensor and the infamous oil screen below it. I’ve done this several times over the years and that little screen always has crud in it. It’s the Achilies heel of this AFM system.

Although I keep my oil changed often and the pressure gauge showed high, I thought that perhaps there was a problem not getting enough oil to the Valve lifter manifold. I then bought four quarts of oil flush and four 5-quart jugs of Castro’s GTX long mileage oil. I flushed the engine four times then added new oil and filter.
It ran rough and gave me trouble starting at first. Now it runs only slightly rough and codes are still showing the same misses but only about once a minute. I was hoping it was just a crud in the oil issue. I’m facing the reality that the lifters are sticking and may need replacing. I have 190K in this engine and the body’s showing a hint of cancer in spots so my vehicle’s value at this point is so low that it wouldn’t justify buying all the necessary parts.

I hate to retire it because in the last year I put new tires, brakes, battery, oil level sensor. Also I dropped the oil pan and cleaned it out really well. Other than the misfires, it’s still a good vehicle with 125 compression in all cylinders.

My son wants me to give it one more chance by replacing the oil with ATF and running it for only a thousand miles. He has more experience than me and said that it will clean out any crud without hurting anything.

Has any one tried this? What would you recommend?

please ignore the attached photos. I wanted only one and somehow other unrelated ones attached also.

 

[kbuskill]

My ‘07 Yukon suddenly shows misfires in #7. And cylinder #2 shows about a third as much misfires. First I threw parts at it(plugs and coils) with no difference. That was just a stupid waste of money. Then I replaced the oil pressure sensor and the infamous oil screen below it. I’ve done this several times over the years and that little screen always has crud in it. It’s the Achilies heel of this AFM system.

Although I keep my oil changed often and the pressure gauge showed high, I thought that perhaps there was a problem not getting enough oil to the Valve lifter manifold. I then bought four quarts of oil flush and four 5-quart jugs of Castro’s GTX long mileage oil. I flushed the engine four times then added new oil and filter.
It ran rough and gave me trouble starting at first. Now it runs only slightly rough and codes are still showing the same misses but only about once a minute. I was hoping it was just a crud in the oil issue. I’m facing the reality that the lifters are sticking and may need replacing. I have 190K in this engine and the body’s showing a hint of cancer in spots so my vehicle’s value at this point is so low that it wouldn’t justify buying all the necessary parts.

I hate to retire it because in the last year I put new tires, brakes, battery, oil level sensor. Also I dropped the oil pan and cleaned it out really well. Other than the misfires, it’s still a good vehicle with 125 compression in all cylinders.

My son wants me to give it one more chance by replacing the oil with ATF and running it for only a thousand miles. He has more experience than me and said that it will clean out any crud without hurting anything.

Has any one tried this? What would you recommend?

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ATF in the oil is an old trick to clean sludge out of an engine. The idea is that ATF has more/better detergents in it that help to dissolve the crud, thereby cleaning the varnish and sludge out of the engine and trapping it in the oil filter.

Another good option is Kreen. It is a product from Kano labs. It is, in my opinion, the best on the market for cleaning an engine but you have to order it online and they do not ship to Comifornia.

 

[Foggy]

IF you do the ATF method... Don't leave it in there that long..
Maybe just a few miles.. Or just a couple of idle/cool downs.
It does not have the protection for your bearings etc that oil does

 

[donjetman]

Use this oil
https://www.tahoeyukonforum.com/threads/oil-consumption-another-fix.115481/

 

[OR VietVet]

You said "replacing the oil with ATF and running it for only 1000 miles". Do not remove all oil and put nothing but ATF in the engine. That is what your statement says. You can use fresh oil and substitute ONE quart to 1.5 quarts of ATF and then run about 50 to 100 miles but no more. ATF is high in detergents and will help clean but never all ATF and not more than the miles I stated.

Then drain the oil and fill with fresh quality oil and a new filter and be ready to change the oil and filter again in about 500 miles because of the crud that was loosened up with the ATF that is still in there. The new filter that was on during the initial ATF and oil mix will get most of it but the remnants will still cling inside the engine during the drain process and that is why you should drain and new filter again after the 500 miles.

 

[91RS]

Do NOT run ATF only in place of engine oil and certainly not for 1000 miles unless you want to buy a new engine. You only run like a quart and drive it for maybe a day very easy. Still, that's a risk I wouldn't take on a high mileage engine. Your problem sounds exactly like mine, same cylinder also. It misfires above 2k RPM. You very likely have a lifter on the way out that hasn't failed completely. Time to delete the AFM hardware or swap in a 6.0L without AFM.

 

[91RS]

Do NOT run ATF only in place of engine oil and certainly not for 1000 miles unless you want to buy a new engine. You only run like a quart and drive it for maybe a day very easy. Still, that's a risk I wouldn't take on a high mileage engine. Your problem sounds exactly like mine, same cylinder also. It misfires above 2k RPM. You very likely have a lifter on the way out that hasn't failed completely. Time to delete the AFM hardware or swap in a 6.0L without AFM.

 

[jcb2]

I put straight ATF in there and ran the engine for an hour. Then I promptly drained and added new oil and filter. There was no crud or anything that came out, only clean fluid. I was hoping that the cyl #s 7 and 2 lifters would stop sticking but it didn’t work.

I priced out the parts to replace the VLOM, lifters and guides. That alone was well over a thousand. And since dealing with #2 opens up an even bigger problem since it’s not an AFM cylinder, I gave up and kissed it goodbye. Since the engine needed major work or replacement, the dealer only gave me $1,000. I traded it in for a certified presented 2019 Suburban with 41K miles on it. I assume Suburban owners are still welcome in this group. I hope so because you folks are great!


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