Z22SE Randomly Runs Rough (3 cylinders)

ZippyZafira

Ok so i have an astra 2.2 with the Z22SE Engine here that use to be mine (never had an issue for me but does to the new owners)
Here is whats been happening
Car was having issues with the starter motor whining but not cranking the car over (randomly) So 3 starter motors later i think i resolved the issue by moving a second earth lead from the negative terminal to the head of the motor. (car already had a second earth installed and was connected to the block at the usual spot so i assume it must have a history of a bad earth)
The car was also randomly experiencing trouble where it would suddenly drop a cylinder and run on 3 cylinders (if you gave it a boot full it would fix it )
Since i moved the the secondary earth strap we have not experienced and issue with the starter not cranking but the random drop in a cylinder is still happening (totally random maybe once a week)
Here is what i have done to the car
New Timing Gear
New Balance Gear
New Water pump
New Temperature switch
This work was all done while i owned the car and i had it for 12mths no issues

Since the issue started i have
Changed Intake manifold
Changed Spark Plugs
Changed Coil Pack
Changed Throttle Body
Change Injector rail and injectors
Changes Tempreature Sensor (again)
Changed Crank Sensor
Changed Oil Pressure Switch.
Changed Front 02 Lumba Sensor
Changed Catalytic Converter
Changed Thermostat
Changed Battery
Changed Starter Motor
But the issue still happens randomly (can't find anything that triggers it and only lasts 10-30seconds or if i give it a boot full)

Things i have noticed
Temperature never gets above 75 degrees celcius (very cold) even after changing thermostat and temperature switch its still the same
The second 02 sensor very rarely gets a signal (sits at 0.0v most the time) but goes through the roof when running rough indicating a lot of unburnt fuel

Despite the car randomly dropping a cylinder and running rough it otherwise idles smooth, sounds great and runs really well

Im just glad i have a million parts here that i can swap over to try and locate the issue

There is also no error codes showing

Car is a manual

vocky

pretty much the only thing which gives no error codes and a mis-fire is the coilpack.

Otherwise it will be mechanical, like a sticking valve or dodgy lifter.

ZippyZafira

The head on the car is basically new.. have has sticky valves and lifter before but this is different
have swapped the coilpack and no fix 🙁

I have been dreading it to be an ECU issue as this car does not have a security code listed for a clone

ZippyZafira

Also brings me to my next question
This car is a Holden and usually getting security passes is not an issue except for this car as holden don't have it listed (something to do with opel at the time)
does anyone know an online place where i could try and get the pass so i can clone the ecu (have a couple of spare blank ECU's here spare)

ZippyZafira

well we finally tracked the issue down
problem is that the car required an 11tooth starter motor after the genuine failed and has been fitted with a 9tooth
can't believe this has caused so many issues