vr v6 082 spark issue

[pgibbo]

I have a strange spark issue. cyl 2 4 6 normal cyl 1 3 5 spark half as many times per rotation. it appears as if has dropped wasted spark on 1 bank only.
anyone got any ideas what could cause this.

[immortality]

How (well) does the engine run, does it run?

IIRC, the VR V6 was the first motor to run split bach fire, using the cam sensor to figure out where it was in the engine cycle to split the 2 engine banks (before the move to full sequential injector for the ecotec)

The amount of spark energy discharged depends upon the resistance in the circuit, a cylinder under compression loaded with the proper fuel/air mixture presents a very high resistance (at the spark plug) and requires a lot of energy, conversely the matching cylinder on the other bank on the exhaust stroke shows much less resistance across the spark gap and therefore draws much less energy. A spark plug in open air provides almost no resistance and almost no energy required to create a spark. The coils can't decide which cylinders get spark, it fires both spark plugs. Not likely to be bad spark plugs or leads if they do indeed spark every other cycle so something else must be influencing it. Have you tried a different DFI/coil packs (not that I think the problem lies here)?

Does the engine run? It would seem that one bank is probably not running, is it getting fuel (do the injectors pulse) on the bank with the odd spark issue?

[pgibbo]

the engine runs but not smooth.
has inj pulse on all cyl. it starts and runs ok then as is settles to idle becomes unsteady.

[pgibbo]

new dfi coils plugs & leads

[immortality]

What do (did) the spark plugs look like on the bad bank?

[pgibbo]

all plugs look a bit rich ( early stage of tune engine has mild cam ported heads and turbo) ve is safty rich but wont stay steady

[immortality]

How are you checking for spark?

[pgibbo]

im using a timing light.

[delcowizzid]

The timing light will act funny on one bank as one bank fires the sparkplug to earth and the other bank fires from earth to centre electrode. Try turn the pickup for the light around the other way and the half flashing will change banks.