Dead miss #1 after all dod lifter replacement

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cretecrawler

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2006 envoy denali 5,3. 159150 miles. Had number 1 cyl lifter failure so brother in law replaced all dod lifters. After reassembly has number 1 misfire so swapped spark plug, fuel injector, coil pack and wire. They thought it might be an oiling issue so the oil pressure sensor and the screen below it was removed and cleaned. Any ideas where to go from here?
 
A compression test is where you need to start at, and maybe a smoke test as well. Need to see if the compression is going into the crankcase, intake, or exhaust.
 
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Another suggestion is to pull the valve cover off related to Cyl #1, and see how the valves are moving. Is the #1 valves moving as well, and as much as the ones in Cyl #3 or #5.

I am surprised you didnt just do a DOD delete. The DOD system is 1 of 2 variety's. Those that are going to fail, and those that have failed.
 
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Maybe an oil valve in the VLOM failed. If keeping DOD, the VLOM should be replaced. It could be allowing oil pressure through when it's not supposed to and actuating the lifter. The was a defect in the original VLOM that is supposed to be replaced when it's being repaired.

Another reason why it should just be deleted.
 
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I am recovering from a motorcycle accident, and the reason i was riding the bike was because the truck was down. So my brother in law offered my wife to take it to his shop and have his shop mechanic take a swing at it. So they decided to put it to stock, i sent him videos on performing the DOD delete but he forgot to watch them. He did buy all the parts and pay the labor. The VLOM was replaced and a compression test was even among all the cylinders.
 
So then it should be diagnosed as a regular misfire since compression is good. So now look at fuel and spark. Maybe the injector is unplugged, defective or has a wiring issue. An injector balance test, if he has a scanner capable of doing it, should confirm this. And of course check for spark.
 
They switched and replaced the number 1 injector, switched coils and wires and replaced number one plug . So maybe wiring to the coil or injector, but I smell raw fuel so maybe it is more to the wiring to the coil?
 
If smelling a lot of fuel, I would think so.
 
Ok put an adjustable Thaxton 404 tester set at 25kv and this is what I got. Seems intermittent to me...but it doesn't drive like it is intermittent. It does smooth out when not under load.
 
I dunno. That looks like a pretty big gap to jump. Is that an automotive spark tester?
 
So spark is good. Verify injector is getting pulse. If injector is new, plug is new, and coil is firing that hard... Then it's an internal problem which would cause compression issues which have supposed to been ruled out.

Make sure injector is getting pulse and is actually firing fuel.
 
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It is possible that it's still sparking but weak. You could swap coils from one to another and see if the misfire follows or not. All else being good, that would leave a fuelling issue.
 
Ok so after driving it easy for a week or so it has developed a louder (tick) *knock and I shut it down and parked it. As I have now revisited under the hood, pulled the d/s valve cover and found #1 intake rocker not moving. Not sure if this is the same lifter that failed originally, although it is the same cylinder. The difference now is that it is much louder.
 
Had DoD been deleted? If not, the lifter has probably failed. Recommend dating the whole system.
 
It could still be saved but still have to deactivate DOD in the PCM. Look on YT for videos on how to get the lifter unstuck using a modified pushrod. The parts may still be salvageable but DOD will have to remain off forever.
 
Tune is preferred I'd assume, that's what I'd recommend, kill it from the source. Has been talk of unplugging the pressure sensor on the brake booster (if you have such sensor) which will trip the system to an off state due to failsafes. Been a while since I read about it but I seem to remember that'll trip the check engine light as well.
 
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Yes, a tune is preferable as it will also turn off the CEL and codes for it. Just $99 at lime-swap.com and get some other benefits at the same time. That's IF you can get that lifter unstuck. You can temporarily unplug the vacuum sensor on the brake booster to disable it until you get the tune or permanently but you will get the CEL.
 
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