Erratic idle, need some advice and expertise on what is "normal&#3

[HogSlayerz]

First off, thank you for all of the great information on your forum. I have read it (and other 5.3 related forums) thoroughly over the past few months as I have worked on a 2004 5.3 LM7 out of a Chevy Tahoe. I know this is a long post and I appreciate any guidance or suggestions you guys can provide.

Brief back story: I bought a 1984 Jeep CJ7 that had a 2004 5.3 swap from a Chevy Tahoe. It has different exhaust manifold so that it can clear the CJ7 frame. The rest of the exhaust appears to be 2.5", has cats and goes into one pipe after the cats. Transmission is a SM465. Engine has about 95K real miles on it. It sat up for a few years being used rarely, and it wasn't running right when I bought it.
When I bought it, it did not run well. Threw lean codes frequently. Soon after starting throwing knock sensor codes. I found out lean codes were from a leak in the brake booster after a few months.
I believe the computer was adjusted by Novak for any of you familiar with Novak and their Jeep swap services.

What I have done since I bought it:
Cleaned up wiring, found many loose connectors, etc.
New AC Delco iridium spark plugs (looked like orignial plugs when pulled)
New AC Delco spark plug wires
New Coils
New brake booster (to fix intake leak problem)
Removed and cleaned throttle body thoroughly
Replaced both knock sensors and harness, siliconed around the plugs (there was water in the rear sensor, was throwing a code
Cleaned MAF
Replace with "new design" intake gasket
Ran multiple tanks with seafoam, techron additive, etc.
Dropped fuel tank and cleaned it out (found some dirt and sand in it, Jeep was from Utah)
Cleaned fuel lines
Fabricated a new in-tank fuel pump, verified fuel pressure at the rail
Replaced all fuel filters (plenty dirt drained out of them)
Last but not least, fixed a long running leak in the brake booster, which caused a significant intake leak/lean condition whenever applying brakes.

This is my first Chevy motor, so I'm not sure what is "normal". The engine runs 99% better than when I first bought it. I'm still having problems with idle fluctuations.

Questions:
#1
When in closed loop, the idle will jump from 520ish to 580ish (sometimes going outside of this range). This seems like a huge range, and I have checked for other intake leaks at least 100 times. I've never seen an engine vary this much and it feels "rough" when sitting in the Jeep.
The engine feels perfectly smooth when you give it gas and get the RPMs above 700 or 800 RPMS.
Is this variation in idle RPMs normal?

#2
When I first bought the Jeep, it would have multiple hard hesitations when moderately accelerating in 3rd gear. Would most commonly happen if you shifted early, starting in 3rd around 1000 or 1200 RPMs and pushed the pedal to accelerate. Engine never threw a code, but it jerked hard and all passengers could feel and wonder what was up. With all the work I did above, the hesitation is mostly, but not completely gone. Any ideas on what to look for next?

#3
When downshifting coming to a red light, when I press the clutch while in second gear to coast to the light, the RPM will drop to 300 or lower for a second or two before recovering to 550ish. 1 out of every 15 or 20 times it will drop far enough where the engine will kill. Any ideas on what this could be?

#4
The engine runs around 195 degrees when heated up. I have read many threads that it should be closer to 215. Is that correct? Should I try to replace my thermostat to get it closer to a 215 degree operating temperature?

#5
No matter what I do, I never get misfire codes (current or history) through the Torque app. Is it possible that the computer is tuned to not throw them? I can disconnect the coil or fuel injector, but still no code.

I have the parts and will be doing the following work over the coming weeks:
Will send off all 8 injectors and the rail to InjectorRx for sonic cleaning.
Have 2 new AC Delco O2 sensors to replace the pre cat O2 sensors. The current sensors appear to test well, but thinking they may be sluggish?

I know it's a long post, but I'm looking for some expertise from folks that know these engines. I have put a lot of work into the engine and reading your forum to try to get it running like new. The problems I have listed above are really stumping me and are the last few issues that are keeping this 5.3 from purring like new.
I have the Torque app with a bluetooth OBDII, so I can get specific information if that will help point me towards the correct diagnosis.

[Swimmer8366]

Sounds like you have a misfire just not getting the codes for it because it's turned off...

 

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[HogSlayerz]

Sounds like you have a misfire just not getting the codes for it because it's turned off...

 

Sent from my Z981 using Tapatalk

I didn't know you can turn them off. That makes some of this makes sense. Am I correct that the idle should stay around 550, only varying by a few rpms?

[Swimmer8366]

Yes. With most Chevy engines that is where should be.

 

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[HogSlayerz]

Any idea on how I should proceed? I removed the fuel rail and watched all the injectors spray. Not saying they all sprayed perfect, but they sprayed.

I'm going to replace the driver's side valve cover to the new design and replace all the valve guide seals this weekend. I will do a compression test while I'm doing the valve guide seals.

 

I'm really lost at this point. Many of the plugs had oil on the threads when I took them out, which surprised me. I haven't seen a drop of oil leak anywhere on the motor, it's clean and bone dry.

 

Also, why would someone turn off the misfire codes? I'm not sure I see the benefit in doing that?

[HogSlayerz]

To give you an example of RPM data, this is logged from torque. It shows the variation I spoke off. RPMs recorded about every minute. Average is 552, which is what I would expect. But look at the up and down variation:

 

557.25 559 553.25 563.25 536.75 547.25 555.5 554.25 533.5 539 561 543.5 550.75 541.5