2006 Silverado 5.3l

Tcwest38

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May 15, 2024
6
Rochester, texas
I have a 2006 5.3l that I put a new rebuilt engine in due to very high mileage and bad camshaft. afrer re-install engine has misfire on cylinder #5, (according to Chevy house, they performed compression test and all cylinders seem ok, they changed coil packs (interchange with other cylinders) and still is on number 5 any ideas? Truck idles rough and will barely get up to around 45 mph
 

azswiss

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May 23, 2021
938
Tempe, AZ
I would look into a couple of additional items to check/swap between cylinders: plug wire, plug & injector. Assuming you have a reader that can display misfire counts by cylinder, start simple, swap the plug wire. Moving on to the plug, inspect then swap with the same cylinder as before. Rinse & repeat with the injectors (check the injector wire and connector as well).

Question: did you verify compression yourself? If not, I would recheck all cylinders to confirm they are all good and within 10% (highest to lowest).
 
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mrrsm

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Best Guess? Bad or Stuck Fuel Injector on the #5 Cylinder:

 

Tcwest38

Original poster
Member
May 15, 2024
6
Rochester, texas
I would look into a couple of additional items to check/swap between cylinders: plug wire, plug & injector. Assuming you have a reader that can display misfire counts by cylinder, start simple, swap the plug wire. Moving on to the plug, inspect then swap with the same cylinder as before. Rinse & repeat with the injectors (check the injector wire and connector as well).

Question: did you verify compression yourself? If not, I would recheck all cylinders to confirm they are all good and within 10% (highest to lowest).
I have not checked myself, was talking their word for it as the guy working on it has over 40 years as him mechanic
 

Mooseman

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Dec 4, 2011
25,605
Ottawa, ON
Check for an actual spark at that coil. If you have spark and compression, only one thing that would be missing is fuel. Check for power and trigger at the injector. A noid light (LED) works well for this. Another test is an injector balance test but this requires an advanced scan tool.
 
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mrrsm

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Roger That...

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TollKeeper

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Dec 3, 2011
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2006 would not have AFM
 

Tcwest38

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May 15, 2024
6
Rochester, texas
Ok guys, this is update after checking compression, all spark plugs were new when engine installed. As you can see all the plugs on1,3,5,7 look like they have never fired or just very clean compared to the others, anybody ideas?
 

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TollKeeper

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Dec 3, 2011
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Check for spark coming out the coils. They do look way to clean.

90-95 PSI is certainly not optimal for a LS in firing. But the rings could be washed out from no-spark condition.

All cylinders should be 150 and up, optimal in the 180-190. 120 Will work, but the engine is getting weak at that point.

Get that spark checked for 1-3-5-7. Work from there.

Did you have your foot completely on the floor on the throttle pedal while you were turning the engine over?
 

Mooseman

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Dec 4, 2011
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Ottawa, ON
If all cylinders on one bank isn't firing, I would definitely check the main connector for that bank, either for the coils or the injectors.
 

Tcwest38

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May 15, 2024
6
Rochester, texas
Note: i did another compression test after adding a little bit of oil to cylinder 5 and compression increased to 150 psi, isn’t that a sign of poor rings
 

TollKeeper

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Dec 3, 2011
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Brighton, CO
Thats a wet test, and I believe that means its good. I would have to find the thread where we talked about that.

What color is the spark on each coil. You are looking for a clear definable blue.
 

TollKeeper

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Mooseman

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Dec 4, 2011
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Ottawa, ON
If compression increases with a wet test, it means the rings are weak/worn/gummed up. You could try using some ACDelco Top Engine Cleaner to free up the rings if they are gummed up. Some have seen success doing this.
 
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mrrsm

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Here are some links to prior Threads that cover the topic of using the ACDelco TEC (Top Engine Cleaner). The Principles apply for the Inline 6, V-6 and V-8 Engines::



 

Tcwest38

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May 15, 2024
6
Rochester, texas
Ok, after yanking the engine again, before I removed the heads, I removed rocker arms and pushrods. I decided to run another leak down test, still have a few cylinders leaking through intake valves (can hear it) is this acceptable?
 

mrrsm

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"...after yanking the engine again ..."

Recommend the Complete Engine Heads Re-Build be done by a Local, Competent Machine Shop if you can afford to do so. If not, and you want to attempt the "Valve Jobs" and De-Carbonizing and or Valve Guide R&R needed, there are rafts of YT LS Engine Head Re-Build Videos available to study these procedures at a comfortable remove... and while confirming with certainty what the Engine Head Part Numbers are so as to obtain the exact Replacement Parts necessary for performing this otherwise ...daunting task.
 
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Mooseman

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Dec 4, 2011
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Ottawa, ON
Since it's intake, they likely just need a good lapping. With the engine out, it's a good time for a refresh.
 
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