VZ v6 running issues

[davideast86]

Can someone please give me an idea of what is happening, my vz is doing all the common things that you read what vz's do, the engine shutters, cylinder misfires, check powertrain light comes on etc etc... I got a diagnosis scan done and it came back with cylinders 2 4 & 6 were all misfiring and flow through cat was too low, I took it to an exhaust place and he said its isnt the cat that is causing the problem and it could possibly be coils, I then went to a mechanic to have a look and found that the coil packs were relatively new and it couldn't be them and that it would have to be an ecu issue. I had a guy that specializes in the computer side of cars and he couldn't find anything when he plugged his computer into the car and said its not a computer issue. So now I'm back to square one and dont really have any idea what to do next. ...

 

[321abstract]

I don't really know much, but I gather if the engine is misfiring it could be spark plugs,leads,coils, would be worth replacing them just to find out if it fixes it + if you haven't replaced them in a while, but another member will be able to help out alot more.

 

[Hrd455]

What kind of mechanic would pull the coils out and not check spark plugs for engine misfire

 

[commodore665]

check your spark plugs ,

 

[diysv6]

Hi,
I offer this in good faith. This is how I see the VZ spark circuits working. Maybe other members can flesh out my comments with the locations of the two earth points on each side of the engine block/cylinder heads.

In the alloytec, looking around the VZ battery feeds and earths, there is a fuse 15A "ign/inj even" feeding 12V to the three ignition coils under the bonnet near the battery. This 12V feed is split to coils 2,4 and 6. Maybe that fuse is dirty or faulty or the wiring faulty?

In passing, the other fuse 15A "ign/inj odd" feeds 12V battery to ignition coils and injectors for cylinders 1,3 and 5.

Also, each ignition coil has two separate earth connections, which go to separate earth connections somewhere on the engine block or on the cylinder head.
One earth is the return for the ECU's signal to trigger the ignition coil, the other earth is in the earth circuit for the high voltage spark.

Each coil's earth connection is joined to the corresponding earth on the other two ignition coils. This way they keep the signal earth away from the high voltage earth. Could cause crossfire or ECU damage?

I have seen sketches of the arrangement, but I think this is how it fits together. Maybe one or both of your earth terminals are loose or corroded for cylinder bank 2,4 &6, especially if some access work has been done around the top of the motor at some time.
Hope this helps.

18 August 2014:
I had a look around the cylinder heads of my alloytec.

I found a terminal lug bolted to the even cylinder head which has two wires attached. The mounting point is above the midway point between exhaust ports 4 and 6. The wiring is enclosed in a protective sleeve and enters underneath side of the wiring form "box" which runs along the outer top edge of the cylinder head. I think this might be the earth wires' from the common point for the low voltage and high voltage spark in the each coil on cylinders 2,4 & 6.

 

[Wats_in_a_name]

Not sure if this will help but I had an issue with my car missing a beat and the "check powertrain" warning came on with the alert beeping noise. I had a scan done and it was one of the injectors (one only) playing up and was fixed for $210.

 

[davideast86]

I have taken it back to a different exhaust guy and he done a heat test over both the cats,the cat on bank 2 which is the one that the scans say is too low was about 86 degrees and the other cat had a reading of 287 degrees, he said that the second one is gone and needs to be replaced and that all the misfires and running roughly would stop once I done that, does this sound right or is old mate try to fool me for $400?