Another alloytec random misfire, can't find solution

[Relax98]

Hi all,
Firstly my in laws car 08 Ve alloytec has came up with p0300 random misfire fault, also cylinders 1, 3, 5. RACV told them that two coils were gone and had to be replaced. So I got the job to replace them, only to find fault still comes up. I put 2 new coils into 1 & 2 fitted 2 into 3 and swapped 4 with 5, the fault still did not change. I also checked the spark plus and they all seem fine NGK platinums so I assume they have been changed. The car has 153000 on the clock. It has also had the right side cat changed for a previous fault, one O2 sensors also for another fault. I have tried searching posts on this but haven't been able to find a solution. The car starts fine every time but once revved over 2000 the miss comes back and the left bank is shut down. Also the car won't rev past 4000 is this normal when not being driven?
Any help appreciated

 

[chriso-k]

Correct! The VE has a rev limiter. The computer will not allow revs to exceed past 4K when the car is idle. Mm, definitely replace your plugs. These are not to be taken for granted. The plugs should of been replaced before the coils. Beyond that, You would need to start looking at fuel trims to ensure the car is not running lean on one or both banks. If it is lean, then a smoke machine is the way to go on those. A smoke machine is an easy way of detecting vacuum leaks. Otherwise you could be searching for forever and more!

Hi all,
Firstly my in laws car 08 Ve alloytec has came up with p0300 random misfire fault, also cylinders 1, 3, 5. RACV told them that two coils were gone and had to be replaced. So I got the job to replace them, only to find fault still comes up. I put 2 new coils into 1 & 2 fitted 2 into 3 and swapped 4 with 5, the fault still did not change. I also checked the spark plus and they all seem fine NGK platinums so I assume they have been changed. The car has 153000 on the clock. It has also had the right side cat changed for a previous fault, one O2 sensors also for another fault. I have tried searching posts on this but haven't been able to find a solution. The car starts fine every time but once revved over 2000 the miss comes back and the left bank is shut down. Also the car won't rev past 4000 is this normal when not being driven?
Any help appreciated

 

[Relax98]

So would the holden dealer be the one for the smoke test or should most mechanics be able to do this, they have already spent through holden a fortune on cat and other sensors although they were related to other codes. Is it likeley to have plugs all along one bank be the problem? I was listening for a vac leak and thought I could hear one around the rear of the rhs bank, very hard without the proper gear to hear it properly. Also had new gaskets fitted today.

 

[Relax98]

So after some more investigation tonight I found a vac leak coming from 90 degree fitting at the rear of the drivers side valve cover. The hose goes to a tee then one hose to each side of the plenum. I blocked these off but found no difference, I didn't expect to but worth a try. I then plugged in my code reader and reset the fault and noticed some variations between STFL B1 12.5% and STFL B2 6.25% average fluctuating but B1 always higher.
I also noticed differences with the O2 readings, o2s 11 0.360v -14.85%, o2s 12 0.465v 99.21%, o2s 21 0.690v 11.71%, o2s 22 0.480v 99.21%. Not sure if this info is of any use but may mean something to someone clever on here.

 

[Relax98]

Holden have checked the car today, and have informed me to change the injectors. I cant understand why the misfires are all on bank one. Do all six injectors come off the one fuel line or does it split for each bank.

 

[Relax98]

swapped the injectors from one bank to the other................ still have the fault after re - set of code...