Hey I may not be the quickest or smartest but I have followed the advice here and will continue to do so for any offered, the seafoam intake cleaning did not solve issue. Yes I was concerned about the cats for lack of better understanding and as most stated they were not plugged or the issue. Tried the flammable brake cleaner spray trick to see if obvious intake gasket leak. The other codes are gone and P0300 remains. Grounds have been checked, ECM connections all look/ appear good. Got the Nano/ Tech2 so I could see more and do crank relearn but connections issues there have stalled that process temporarily. Scanner did show for several desired vs actual readings to be good. Injector values were the same between the 2 banks readings. Next step unless better suggestion arrives is attempt again the crank relearn further, since 1& 3 are the main culprits misfiring I'm gonna swap those coils to see if it moves with the coils, and/or prepare to pull intake so I get look at intake valves, fresh gasket etc. Inspect injectors/clean/flow test them. Air Fuel mix was good @ 14.7 for most part. MAF I'm not sure on, will be looking at it again and anything else anyone cares to suggest that I can see with the Tech2 and what the desire value at idle should be. To be clear it will trigger P0300 @ idle.

Happy Thanksgiving all!

 

ive had a few issues with the nano saying it’s disconnected. I don’t know what causes it and usually after plugging it back in it works.
some things I would look at-

-plug the laptop into power

-make sure high performance power plan is selected(it will change depending on plugged in or not so plug in first then select the power mode)

-change auto screen off and sleep time to never

-make sure usb is set to always active/highest performance(it’s in the power management settings when you press customize next to high performance)

-disable any antivirus.

-try not to bump the cable or move the laptop

-try a new cable.

the nano could also be defective. It is China made after all and bad soldering is not unheard of.

 

Thanks Gavin for suggestions. Tried them all and it is truly a PIA plus some Neal had suggested. Looking at data 1 or 2 it seems to be able to reconnect most times. Doing other routines that require continuous connect are next to impossible. I finally got through each one I wanted to run but the Cylinder imbalance it will never allow it to run completely. I'm gonna return it for exchange unless there is another brand of interface that will work with the Tech2 Win software that someone has used with better results.

 

Hope all had a safe n great Thanksgiving. SIL n myself were busy on the H2. Got the hood off and so much better working room now.

While waiting for the Nano I was busy checking items off the list. Big ones were the SeaFoam induction cleaning, MAF and TB cleaning as mentioned before. Finally got Crankshaft relearn done. Did Injector pulse test-readings from the test routine are 1-#51/26 2-#50/24 3-#49/24 4-#49/24 5-#49/24 6-#48.5/24.5 7-#49.5/25 8-#49/24 so they all looked good to me. Could never get cylinder balance to run complete without connection being lost. So went back to swapping components, moved coil #3 which was worst misfire with #7 and misfire stayed on #3 cylinder. Then swapped plugs and misfire then moved to #7 indicating plug was the problem even though they spark and look near perfect burn. Did same process on bank 2 and again saw the plug as the main culprit while watching misfire data. So Nano paid off there as my other scanner I couldn't see the misfires. I'm leaning to those coils as suspect. For lack of more knowledge I'm thinking weak coils causing plugs to go bad? Something is because 3 plugs bad in total now within 10000 miles of being new. They are the ACDelco Iriduim 41-110's. I went to town and got a set of NGK TR6'S Copper V-Power and for now just put them in those in those 2 holes. I still have very slight misfire but has not thrown code while idling as it would before. Again I'm thinking coil replacement for those 2 to verify they are bad before buying all new.

Now subject of wires- referring back to this post: https://www.hummerforums.com/forum/h...s-47210/page2/ I have the same ACDelco 7mm wires and mine are at 980 ohms average. Not 435 or so. What is everyone's thoughts on wires- Stay with these or go with Taylor 8mm Thundervolts or similar at 1/2 the ohms of these ACDelcos?



ACDelco 7mm Premium wires
Thanks ahead for thoughts and inputs.

 

I can't remember if you said if your fuel trims were out of wack earlier, but if it's dumping too much fuel for volume of air, that will definitely cause plugs to foul. I had an issue with a honda pressure washer not starting last week, ran fine on brake clean, and the plug had a nice blue spark. So I replaced the carb and it still wouldn't run. After all the fussing, I threw in a new plug for kicks and it fired right up. Spark plugs are weird things.

That sucks about the nano though. I don't know what else to tell you about that. Did you use only the included software on the thumb drive? Did it update anything?

Also have you tried clearing the codes with the nano after you did the tune up to see if the other codes like the u code come back? It sometimes is possible that low or erratic voltage from the alternator(due to the misfiring engine) could cause it. I had a buddy's 8.1 2500 throw codes for o2 sensor inactivity and alternator field winding pwm signal out of range codes because it was misfiring so bad due to a stuck injector. He took it to several mechanics who said they couldn't figure out what was wrong. I feel like some of these places just don't want to work on these trucks anymore for some reason.

 

Fuel trims look ok on short term but bank2 wants to sometimes show a -5 on LT. I'm gonna go ahead and change out the coils on the 2 suspect cylinders and in process of pulling injectors for inspection//flow test. I'm in no hurry and already pulled coils off to look at the harnesses for coils and injectors and to clean it all up, re tape/ replace cracking brittle wire looms etc. while I'm waiting on coils to arrive and the injector guy is hour away so will carry them over for that. After changing plugs it didn't throw a code as it would immediately at idle. But I could see on the misfire screen a slow count on those 2 cyl. Thought it can't hurt to give it all a good look over. Gonna wait on pulling intake till I see what all this tells me. I realize knock sensors will likely at some point need replaced but for now if I don't need to I'm gonna wait. Give me something do do later, lol. But if all this still leaves a slight misfire then intake will come off for gasket and to inspect.

The Nano was the software on thumb drive and I believe it did update something. The computer I'm using has no AV as it's only used for engine diagnostic software and nothing else. The last use I did the license update again and it lasted a bit longer than before but it still went back to losing connection. I will send it back for exchange just to see if it makes a difference.

Thanks for help!

 

There is 2 items to update, the firmware and the manger program
The nano firmware is done once the manager is connected to the nano and you select firmware update, it should show you the current firmware on the nano and the most recent firmware available, if they match then your good there.
the manager update is in the lower left corner of the manager screen, a little cloud icon that will download the update from AllScanner, it will let you know if it needs an update when you select the cloud. next to the cloud icon will be the current manager firmware number.


current firmware for both from mine.

have you tried disabling your anti-virus software and adding the nano software to your firewall exceptions list?
both will interfere with the software install,

Neal

 

Your injector test looks good to me,
I think the plug wires look good also
I have a set of new LS plug wires that are a little longer than what you have, I just tested them, they all read between 1000 and 1100 ohms

Neal

 

Neal,



Yes I have the programs enabled thru firewall and I don't have Anti-Virus on this computer. Screen shots attached show it thinks I'm current but by your screenshot there is a newer firmware by a couple weeks. 1 thing is the low voltage warning and it gave that to me from the 1st load, but it went thru the process and updated. When connected to H2 voltage is good on manager screen and in TECH2 data stream.

Anyway, i just dealt with Amazon 2 hrs ago on the return and I'm ordering another for the hell of it to see I can be lucky and it is the Nano itself. I doubt it but worth try, seems like a lot of people have this issue. I'm waiting on coils to arrive and be hunting next 4 days so by time another Nano arrives I will have it back together and ready to test again.
Painted valve covers today and with harnesses off they look good. Injector harness looks good as well and based on injector balance/ pulse test I did, the injector guy really believes they are good to go and waste of money for him to flow them. I have bank 1 injectors and rail off and they visually are clean. Test pressures were good so I'm gonna pass on the flow/ clean for now. See what the new coils and new plugs do and if it lasts and doesn't pop back throwing code out on a road test.

Be a week before that happens. Thank much again and you all have been amazing help! Roy

 

Got my new GM coils today and a new Nano. So the new coils completed and ended the mis-fires with it in my shop idling for 30 mins. Before it would trigger the DTC within 2-3 mins of idling. Counter was absolute zero on all cylinder's. Awesome and big thanks to all of you for the various suggestions. Each needed to be done whether it had a direct bearing on the mis-fires or not. Late next week I should be at the point I can get it out of the shop for a road test. Currently, have the stock tranny cooler out and the radiator cooler bypassed. I had a temporary hose loop on the steel lines for my mis-fire testing today. We're running down to daughters in Knoxville for long weekend so another delay in wrapping all this up. But hell, its mostly sat all these last few years so bit more is nothing new. In my inspection of everything while waiting on the coils and a new Nano, I painted the valve covers while I had them off and got a couple other small cleanup projects going as well on it to finish along with the new tranny cooler.

The new Nano is same as the 1st one. Guess you get what you pay for. It is a great cheap tool but one hell of a aggravation with the disconnects.

Big thanks again to you all.