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Discussion Starter #1
Got a call from the wife the old burb started running rough on the way home from the market. Service engine soon was blinking.
I just told her to park it and I will check it next week since we are driving to Atlanta tomorrow.
Hooked up a cheap OBD2 scanner real quick and got a DTC.
P0305.
Feel free to guess.
This will be an interesting case study.
 

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2000 Silverado Z71 4x4 5.3L 460k+ miles w/ GM rebuilt motor and trans
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Loose spark plug! See my previous post. 馃槈

 

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Discussion Starter #3
Thank you. I'll check the spark plug #5 when I get back next week.
 

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Discussion Starter #4
Wait, I just changed the spark plugs 6 months ago at 285k miles.
It could be the ignition coil, the injector or the fuel pump is getting weak at 148k mile mark now.
I doubt it's the fuel pump though because the misfire is very specific to cyl #5. Otherwise misfire will be across multiple cylinders, P0300.

Lately, my around town driving mpg dropped to 14.
I used to get 17-18. So I decided to change spark plugs today at 285k miles.
First spark plug change was at 130k miles. Second set at 285k.
I tried to find the same AC Delco 41-985 Iridium type but local stores only have AC Delco 41-162 double platinums.
We'll see how they perform after another 15k miles as I am planning to replace the engine at 300k miles with either another 5.3L crate or a low mileage 6.0L engine from a 2500 Suburban or truck.

The second set of 41-985 Iridiums are in bad shape esp the ceramic tips but they are dry (no oily residue). (See attached pic.)
 
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ahhhh heres the info about your misfire, obviously not a "computer reset might fix it problem." like I suggested in the other thread. I simply have never worked on one of these motors and cant help. but I like to learn.

good luck man!

Al
 
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Bazar, what plugs did you use, the 5.3s are fussy.
 

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Discussion Starter #7
Ray, I tried to find the AC Delco 41-985 Iridium type but local stores only have AC Delco 41-162 double platinum.

I'll work on it next week. Hope not to have to fire the parts cannon. Don't have the funds LOL.

Here is my plan. I don't have a sophisticated scanner ($$$). I only have a $30 scanner. So back to basics.
1. Spark test. Use my antique timing light to confirm presence of coil secondary high voltage.
2. Redundant spark test. Swap coils and wires between 3 and 5 and see if misfire follows the coil.
3. Temperature scan on cylinder #5 exhaust manifold to check for combustion and compare to other cylinders.
4. If exhaust temp is low compared to other cylinders, I will perform an Injector #5 flow test.
 

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I personally dont think that the platinum ones are right. iridium tipped is what I understand is what is now recommended in the 5.7 vortecs, that's what I have in mine anyways I dont know what your 5.3 calls for.

if it is because of a faulty sparkplug it could really be because of a counterfeit copy cat sparkplug. heres a some relevant info...

 

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Discussion Starter #9
Shoot, I hope they were not China crap.
 

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Discussion Starter #12
Yes, @Jaercole , I will include that in my tests next week. Thanks.
 

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Discussion Starter #13
Ray, even though the platinum plugs are only 3k miles on them, I will plan to pull out cyl #5 spark plug. You'll never know when the ceramic insulator will crack and show carbon tracks.
 
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Discussion Starter #14
Update on the P0305 misfire.

1. Using a timing light on cyl #5 spark plug wire, I have high voltage spark from the coil.
2. No need to swap coils between 3 & 5 based on result above.
3. Took exhaust manifold temperature reading on cyl #5, cyl #3 and cyl #7 with an IR thermometer.
Cyl #3: 310F
Cyl #5: 210F
Cyl #7: 305F
4. There is no combustion on cyl #5 due to low exhaust temp.
5. This is an injector issue or absence of fuel.

Idle is still rough and missing at higher rpms. DTC P0305 came back after reset.
I will test the injector #5 tomorrow.
 

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what a great idea! I finally got an infrared thermometer and its extremely helpful for all kinds of things.
 

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Discussion Starter #17
Getting ready to test injector #5.

Trying to be gentle not to break the plastic connector.
I unclip the safety clip but I can't unplug it. Or maybe I was just too careful not to break it?
Anybody knows how to unplug this bit*h? Don't want to break and create another problem.

Injector connector 3.jpg
 

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Discussion Starter #19
It's ok @Jaercole

Guys, Ray, @j cat , any tips on unplugging this injector connector without damage?
 

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Discussion Starter #20
Googled how to unplug injector.
I had to pull up on the safety clip and pulled it out and just pressed the plug side tab and it pulled out.

Time to set up the 9V battery test rig.
Injector clip 1.jpg
 
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