Ignition timing specs 6g74 auto

[stumagoo]

Thanks for that info but i have read that there is reset procedure that uses the connection on the fire wall and just wanted to read through it just to see if it would cure my issues. You say " there is no wearing or mechanical component to either of these settings.." but the original crank had wear on the timing gear/wood-ruff key which would make the ECU think TDC was different to where it is now(good crank with no wear) and my issues seem to feel like retarded ignition timing

Yes you are correct the woodruf key and the tone wheel can get damaged but that is not due to the normal operation of the engine - like wearing ignition points - that is due to a mechanical failure of the harmonic balancer etc.... normally when it has been removed and refitted or replaced without replacing the bolt that holds it on.

The plug on the firewall is a diagnostic setting plug that puts the ecu into a diagnostic mode that allows the timing to be checked and verify that those items you merntioned and a couple of others have not been damaged or that things are actually timed as per spec. There is no way of altering the base timing if they are out - and if they are out it is because something has broken.

Similar with idle - there is an Idle screw that is sealed and set at the factory - if altering that corrects an idle issue you are just hiding another problem - warn ICV or a vacuum leak or something else - there is not supposed to be any changes to the idle control once set

The ECU has no way of recognising the timing is actually out and altering it to suit a worn woodruff key that is why it needs to be set to the base setting and confirmed with the timing light. if you are down on power from before its likely one of 2 reasons.... 1 the timing belt is not aligned correctly or 2 the worn key was actually allowing the timing to advance (it shouldnt but weird things do happen) a deg or 2 and give you a little more power - issue is this is akin to old school back yard mechanics where kids would advance the dizzy untill it pings then back off a fraction.... great way to melt the pistons

[Bazbad]

Yes you are correct the woodruf key and the tone wheel can get damaged but that is not due to the normal operation of the engine - like wearing ignition points - that is due to a mechanical failure of the harmonic balancer etc.... normally when it has been removed and refitted or replaced without replacing the bolt that holds it on.

The plug on the firewall is a diagnostic setting plug that puts the ecu into a diagnostic mode that allows the timing to be checked and verify that those items you merntioned and a couple of others have not been damaged or that things are actually timed as per spec. There is no way of altering the base timing if they are out - and if they are out it is because something has broken.

Similar with idle - there is an Idle screw that is sealed and set at the factory - if altering that corrects an idle issue you are just hiding another problem - warn ICV or a vacuum leak or something else - there is not supposed to be any changes to the idle control once set

The ECU has no way of recognising the timing is actually out and altering it to suit a worn woodruff key that is why it needs to be set to the base setting and confirmed with the timing light. if you are down on power from before its likely one of 2 reasons.... 1 the timing belt is not aligned correctly or 2 the worn key was actually allowing the timing to advance (it shouldnt but weird things do happen) a deg or 2 and give you a little more power - issue is this is akin to old school back yard mechanics where kids would advance the dizzy untill it pings then back off a fraction.... great way to melt the pistons

As far as i can tell there is no vac leaks(wouldn't that may idle erratic/fast) and no EML on, so the issues are 1-- slow idle (600rpm) 2--- slow/flat engine pick up from idle (holding back like retarded ign timing) but over 3000rpm it goes ok, cam timing checked and triple checked! thanks info so far

[Just Cruzin]

Was the doner crank from a single cam or a twin cam engine and which CPS tone wheel did you use with it?

[stumagoo]

My NL hesitated up to around 3000 rpm it was the upper to lower manifold gasket - I had replaced it twice looking for issues but having finally deciding to live with it the issue went when I changed the plugs on a service and being slack that time used gasket cement and reused the metal gasket - I had checked over and over for vauum leaks and even had it professionaly checked over for them... never found any but it must have had one... aside from that I would pick the ICV is playing up or the AFM is. finally the ecu coolant temp sensor could be - thats the 2 wire one

Mechanically the only thing I can think of that may happen is the butterflyt valve problem the DOHCs suffer from

[Bazbad]

Hi , you are correct about the ICV as I had it on a scan tool and it's shown to be at 100% and not moving so that's the idle issue. Nothing else was out of place so I'm going to be changing the fuel filter and cat then looking at injectors.. Do you do this for a living?