VN V8 trouble shooting - missing , runs rough

[vombil]

Hi guys

I have a VN V8 conversion in an HQ. It idles OK (not great) but under load is absolutely terrible. I have cleaned PCV, replaced throttle body gasket, checked leads (not under load), plugs look old but not dirty or really worn, timing was miles out so I bridged with paper clip and set it to 10 degrees. When I remove the paperclip the timing changes to 6 or 8 degrees (i think).

does anyone know if the diagnostics is worthwhile? - i don't have a check engine light to count flashes

it has o2 sensor and map sensor that are connected etc

suggestions?? tps, map, leads, fuel pressure, dizzy. ignition module, rotor etc etc

 

[EYY]

Make sure you have the leads in the correct order. The ignition module might be causing some problems. I'm quite sure it earths through its casing - how do you have it mounted?

 

[vombil]

thanks mate
first thing I did was check order of leads
i will look at earth module. it's sitting on inner LH guard, same rough location as when in a commy

 

[Circlotron]

Could be the coil breaking down internally.
When you put a bit of load on the motor the plugs need a lot more voltage to fire, and if the coil is a bit sad it will spark over inside instead sending it onward to the distributor. Another possibility is the rotor button, for basically the same reason as the coil. Because they are in such a pig of a place they hardly ever get changed (or in my case, never) and so it might be way old.

I'd try the rotor button first because it is cheaper.

 

[vombil]

thanks mate the button does look a little sad. coil looks original and the motor looks to have done 250kms PLUS!

I found that the fuel reg vacuum line that runs through manifold was chewed out....... wait for it..................RATS!

changed that and it idled better for a while, still missing

found lead #7 was breaking down under load. changed that and the IAC switch on the throttle body. no change. still missing and still idling like a pig dog

it is very slow to respond when you stab the throttle and the with ignition 'ON' i can hear the IAC switch ticking constantly. it's only just started happening (hence why a put a new aftermarket part in). No change with the new part. Still ticking constantly with engine Not running but ignition 'on'
perhaps the computer has some fault?

IM STUMPED!