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Low Range Drifter
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8,118 Posts
Discussion Starter #83
i have a MAF you can borrow to test if needed.
Thanks. I may do that before I buy one.
John, take a look at the crank relearn. I fought this for a year and this solved my random misfires.

http://www.silveradosierra.com/vortec-6-0l-v8/p0300-situational-t12179.html
I will have to see if I can come up with a scanner that can do that. I read a little about people fighting with case learn and wondered if it could be playing a role.

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Low Range Drifter
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8,118 Posts
Discussion Starter #84 (Edited)
Is it lean.... Seen lots of cracked intakes creating a lean miss on specific cylinders.
I'll pull better numbers tonight. I think it was < 5%.

Was looking and 3 to 4 bolt throttle body adapters are on summit for $25-50, so I could likely get to a TBSS intake for around $100 if I have to change intakes. edit: or it could tumble into a giant pile of just 1 more thing...
 

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I'll pull better numbers tonight. I think it was < 5%.

Was looking and 3 to 4 bolt throttle body adapters are on summit for $25-50, so I could likely get to a TBSS intake for around $100 if I have to change intakes. edit: or it could tumble into a giant pile of just 1 more thing...
I have adapter here brand new in the package. Dont go buy one
 

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Low Range Drifter
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8,118 Posts
Discussion Starter #89 (Edited)


This is engine running about 2500rpm in 2nd gear down a flat road in steady state. Short term keeps flipping. Stays under 10%. Long terms are under 5%.

Misfire zone is between 1500-3000. All else seems ok.

Red : Misfire Cylinder 5 (one of 4 cylinders misfiring), counts 0 to 80, resets and starts counting again
Green : Fuel Trim Long Term Bank 1, sits at 4
Blue: Fuel Trim Short Term Bank 1, switches between +6/-2
Purple: Fuel Trim Long Term Bank 2, sits at just over 2
Yellow: Fuel Trim Short Term Bank 2, switches between +4/-4
 

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Low Range Drifter
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8,118 Posts
Discussion Starter #90 (Edited)


Lost some resolution on upload.

Red : Fuel Trim Long Term Bank 1, sits at 4
Green: Fuel Trim Short Term Bank 1, switches between +6/-2
Blue: Fuel Trim Long Term Bank 2, sits at just over 2
Purple: Fuel Trim Short Term Bank 2, switches between +4/-4



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I see 2 5 6 8.

Firing order is. 1 8 7 2 6 5 4 3

No counts on 7 or 3?

Wondering cam vs crank sensor....like slack in chain
 

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Low Range Drifter
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8,118 Posts
Discussion Starter #94 (Edited)
Not sure, but I said f-it and decided to start pulling the drivetrain. Pulled the exhaust manifolds that were leaking like crazy. Was looking to see if I could fix driver's head stud, but decided it was pretty well buried and easier to fix on the stand. Will pull engine apart to check for wear while on the stand.

Spent the rest of the day under the vehicle pulling shafts, exhaust, and unplugging everything. Still have a bunch to disconnect before pulling the drivetrain out.
 

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I would start with a cam/crank relearn once it's in its new home and see if that clears up the misfires.

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skillicous
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were the exh manifolds leaking before or after the O2?
 
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