2006 Jeep 5.7 Hemi Misfire at Low Revs

[Crumpy]

Can anyone please advise where to go next:

2006 Hemi with 90000 miles (in the UK)

Recent Air filter change
Recent oil change
Recent Transmission Fluid Change
Occasionally running rough & misfiring at low revs
Runs on LPG (GAS) and Petrol
Petrol Injectors cleaned (Wynns advanced injector treatment) 2 tank fulls
Gas Injectors cleaned (Ran Carb Cleaner through injectors)
Codes:
P0300 - Random Multiple Cylinder Misfire Detected
P0302 - Cylinder 2 Misfire Detected
P0308 - Cylinder 8 Misfire Detected
Replaced all copper Spark Plugs & Torqued down (needed doing at 90k miles anyway) old plugs look good
Cleaned & inspected all coils
Checked resistance of Coils all OK & reading the same
Swapped coils 2 & 8 with Coils 4 & 6 on same bank to see if code moved no difference
checked PCV valve clean and good suction on hose
Reconnected battery cleared all codes
Started up fine all good no codes recorded
Ran for 150 miles tried gas & petrol all running fine, gave it some hard acceleration
no codes raised
Started the next morning engine code P0300 came on on way to work misfiring and running rough .
Engine revved ok in neutral on gas or petrol, then spluttered misfired and died a few times when put into drive.
Using a cheap OBD II reader, Other spurious codes which appeared once but have not reappeared :
P0608 - Control Module VSS Output 'A'
P0188 - Fuel Temperature Sensor B Circuit High Input
P0208 - Injector Circuit - Cylinder 8
P3441 - Cylinder 6 Deactivation/Intake Valve Control Circuit/ Open
Put into Local garage
EGR valve removed & checked working ok
Ox Sensor seems to be working fine
no other codes except P0300
Replaced Crankshaft position sensor
Cleaned Mass Air Sensor
Throttle Body removed and cleaned
Codes have not come back but still occasionally splutters on both Gas and Petrol at Low Revs and engine light flickers
everytime i disconnect the battery and leave it for an hour then reconnect it runs like a dream for a few days this leads me to think it cannot be anything physical
P0300 was the main code but it has not reappeared yet after 4 weeks however the misfire comes back

Help

[Thrasher]

Have you had the battery checked (and the alternator?) - on a modern RR low battery can cause havoc with the DTC's!

[Crumpy]

Thanks, New heavy duty blacktop battery last year not checked alternator ... would these cause bad misfire when cold ?

will get them checked though 

[Crumpy]

I ran through a couple more of tank full's of petrol with Wynns injector cleaner, sprayed a tin of Wynns Carb and valve Cleaner through the air box and also into the CV valve  ...and put some Wynns lifter treatment in the oil ............ its not thrown and codes running on Petrol in 4 days now ... fingers crossed

[Range Rover Blues]

Sound like something intermitant then, more likely to be electrical than mechanical perhaps.

Is the problem just as bad on both LPG and petrol?  if so it suggests it's not a fueling issue and the clean plugs add weight to that.  If one was black for example I'd think leaky injector.

You can get OBD readers that connect via bluetooth to give you live data as you drive, you could look for a sensor going out of spec as the problem occurs then.

Alternatively do you have the software for installing your LPG system?  mine would allow me to look at things like injector pulse timing as live data, you can use this to see how the ECU responds to the inputs it's seeing.

Just a few thoughts, here's hoping it's something simple and cheap to fix.