× Help us help you. By posting the year, make, model and engine near the beginning of your help request, followed by the symptoms (no start, high idle, misfire etc.) Along with any prevalent Diagnostic Trouble Codes, aka DTCs, other forum members will be able to help you get to a solution more quickly and easily!

Problem child

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24 Mar 2021 18:00 #47727 by scannerjohn
Replied by scannerjohn on topic Problem child
Clear flood test... Hold accelerator to floor while cranking engine. Listen to rythem of starter motor. Should be consistent rem rem rem starter sound. Any hick ups tells you one or more cylinders has a problem.

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24 Mar 2021 18:13 - 24 Mar 2021 18:13 #47729 by welj31
Replied by welj31 on topic Problem child
i swapped plug 8 with plug 2. no scanner says misfire is in cylinder 1/6 WTH? will try the flood crank now.......cranks normal no odd ups or downs
BTW it starts on the 3 rotation
Last edit: 24 Mar 2021 18:13 by welj31.

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24 Mar 2021 18:16 #47730 by scannerjohn
Replied by scannerjohn on topic Problem child
Hmmm. Has to be oil then. Compression on #8 looks Ok, but if oil is in the cylinder you will get a high compression rate as a posed to a dry cylinder. Does the pressure bleed off?

Put your thumb over plug hole and crank. Can you tell now if oil or ?

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24 Mar 2021 18:25 #47731 by welj31
Replied by welj31 on topic Problem child
i am going to re run the compression test wet/dry and leak down test all while its still warmed up. this will take me a while. Will post results asap thank for the help

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24 Mar 2021 18:55 #47732 by scannerjohn
Replied by scannerjohn on topic Problem child
Have to have ignition disabled and all plugs installed. Hold accelerator to floor instead of disabling fuel pump. If already disabled fuel pump ok. Some subscribe to holding WOT when doing compression test but fuel pump has to be off no matter disabled at relay or holding accelerator to floor it stops flow of fuel.

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24 Mar 2021 19:11 #47736 by Tyler
Replied by Tyler on topic Problem child

welj31 wrote: i swapped plug 8 with plug 2. no scanner says misfire is in cylinder 1/6 WTH? will try the flood crank now.......cranks normal no odd ups or downs
BTW it starts on the 3 rotation


The misfire monitor may be struggling because #1 and #8 are adjacent in the firing order. 1-8-7-2-6-5-4-3

But that doesn't really matter - the miss counts moved when you moved the plugs. If you're still proceeding with the compression test, I say swap all the plugs between banks. In other words, take all the bank one plugs and move them to bank two. Recheck your miss counts.

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24 Mar 2021 22:09 #47745 by welj31
Replied by welj31 on topic Problem child

scannerjohn wrote: Have to have ignition disabled and all plugs installed. Hold accelerator to floor instead of disabling fuel pump. If already disabled fuel pump ok. Some subscribe to holding WOT when doing compression test but fuel pump has to be off no matter disabled at relay or holding accelerator to floor it stops flow of fuel.

"all plugs installed"??

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24 Mar 2021 22:24 #47746 by welj31
Replied by welj31 on topic Problem child
compression test results:
1# 178 DRY / 210 WET
2# 178 DRY / 188 WET
3# 178 DRY / 210 WET
4# 178 DRY / 190 WET
5# 180 DRY / 188 WET
6# 178 DRY / 192 WET
7# 180 DRY / 200 WET
8# 178 DRY / 190 WET
I did not notice any leak down on my compression gage, but i will do a leak down test in morning.

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26 Mar 2021 11:17 #47794 by scannerjohn
Replied by scannerjohn on topic Problem child
Yes, all plugs installed. You're checking for uniform compression.

The numbers look Ok. Do you still have fluid on the #8 plug after swapping plugs as suggested?

If oil, can be bad valve seal or intake gasket leak. Fuel could be leaking injector. I'd expect your fuel trims to be off on bank 2.

Did you get it fixed?

I have an 04 Tahoe Z71. It goes through a qt of oil about ever 3k miles. The #2 knock sensor is bad, 108 ohms so it goes off intermittently. Other than that it is a great SUV.

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30 Mar 2021 09:34 #47873 by welj31
Replied by welj31 on topic Problem child
Sorry guys our internet went down during last storm. We will be back at it today. I agree I am thinking intake or valve seal. Leaning towards the seal as I am thinking it's oil on plug along with the smoking (very light blue / white). Do not seem to be loosing any coolant.

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08 Apr 2021 08:53 #48068 by welj31
Replied by welj31 on topic Problem child
Well long story short we installed new valve guide seals (it was oil on plugs). Smoking stopped, misfire stopped and running ok for now. Cant scan at this point to reset code as laptop screen went bad LMAO Thanks to everyone for your help.

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