VY not backing off between gear change

[Corbs1234]

i have this problem in my VZ V6 ute, 6 speed manual.
But only when the motor is cold. once the temp is halfway on the guage, the revs drop instantaneously

 

[stevoss]

i was thinking about this and are you talking about the alloytec/ newer v8's and the Fly by wire throttle??? if so yes you can get the computer mapped so that its more responsive to the actual pedal control, i found it really gay driving an vz ute lol.

 

[BarraSpalding]

Throttle by wire technology sux.

Driving a POS toyota yaris... and the pedal to actual throttle response was out by at least 1 second... being a rental i by-passed this by foot to floor acceloratrix and side step clutch to get going in a hurry p

 

[atlasdn]

yeh i know what mean,my gts coupe does this also and as your letting the clutch out the revs just dissappair making you look it a fool bunny hopping down the street!!! good to see it must a common prob...

 

[whitey66]

The reason it does that is for emission control,it allows extra air into the cylinders while decelerating to prevent a temporary rich mixture.If the throttle were to just snap shut and the IAC (idle air control) valve to do the same,there would be a normal amount of fuel in the manifold,with a less than normal amount of air (for that engine RPM), so you would get a rich mixture.
Hope this makes sense to everyone,but that's exactly why it does it.

 

[enhancedss]

The reason it does that is for emission control,it allows extra air into the cylinders while decelerating to prevent a temporary rich mixture.If the throttle were to just snap shut and the IAC (idle air control) valve to do the same,there would be a normal amount of fuel in the manifold,with a less than normal amount of air (for that engine RPM), so you would get a rich mixture.
Hope this makes sense to everyone,but that's exactly why it does it.

No this is not correct, on quick throttle closing you will enter decel fuel cut, so you will have no fuel going into the engine. The problem happening with the vehicle is caused by the ECU controlling the IAC motor with the amount of steps that have been programmed into the tune.

On decel the idle speed control motor wont close the IAC port as the engine will stall.

It might be that the base throttle stop is either to low or to high and the ecu is compensating for this.

 

[whitey66]

No this is not correct, on quick throttle closing you will enter decel fuel cut, so you will have no fuel going into the engine. The problem happening with the vehicle is caused by the ECU controlling the IAC motor with the amount of steps that have been programmed into the tune.

On decel the idle speed control motor wont close the IAC port as the engine will stall.

It might be that the base throttle stop is either to low or to high and the ecu is compensating for this.

Ok,so if what you're saying is true regarding decel fuel cut,how can the revs increase?
No fuel equals less RPM than some fuel don't you agree?
They don't go to decel fuel cut the instant you close the throttle,connect your scan tool and go for a drive and see.

The IAC valve closing won't stall the engine because it still has the "base idle" setting,that is made with the IAC in the fully closed position.Maybe if the engine is cold it might.
I wasn't saying that when you closed the throttle that the IAC closes,if you check what I wrote you will see that I said "IF".
If you remember back to the days of carburettors,the later ones were fitted with a dashpot that slowed down the closing of the throttle plate,this was fitted for emission control reasons,as well as driveability.This is the same thing only it's done electronically.

If you read the OP first post he is saying that his problem is a "Slow return to idle after the clutch is depressed" if it did go into decel cut mode as you imply,it would stall.

 

[enhancedss]

If there isnt enough base idle air going through, the engine is relying on the IAC to control Idle, if the IAC motor is compensating for this, the IAC motor will work at higher steps, the more IAC steps, the more air into the engine.

When backing the throttle of, manifold vacuum going up, and decel fuel cut gets engaged. If the IAC steps are to high, its like a massive vacuum leak and air flow will see show to high on the Maf sensor, so decel fuel cut wont be enabled.

No fuel into an engine wont make the rpm increase, however it will still slowly decrease.

Alot of manufactors stopped the idea of the dashpot, once catalitic converters were released.

So what your saying in all this is, Holdens released 100,000 manual cars 99% of the cars on the road dont suffer from this problem, and 1% have the problem, so how can this be an emission control.

What about larger cube engines eg LS1 series cars, why dont they have the same problem, after all they do have more emissions.

Personally what i would be doing, is clean the throttlebody, check and reset base idle air, reset fuel trims, and retry the car.

 

[whitey66]

They all do it,only about 1% of people complain about it obviously.
When the VYs were first released I had 3 or more cases with Holden Technical Assistance Service (TAS).Their engineers advised that this was normal and for emission control,but maybe you know more than the guys that built them.
LS1 engine management was far superior than what the VY V6s were running,it could be programmed better to have more control of this problem.
The way it was done on the VY V6s was a stop-gap measure to comply with emission standards till the new engine was released imho.

Regarding the deletion of the dashpot on models with catalytic convertors,can you be more specific on what models did this??
The reason most of them deleted the dashpot with catalytic convertors was because they mostly had fuel injection .

 

[VZ_SS]

They all do it,only about 1% of people complain about it obviously.
When the VYs were first released I had 3 or more cases with Holden Technical Assistance Service (TAS).Their engineers advised that this was normal and for emission control,but maybe you know more than the guys that built them.
LS1 engine management was far superior than what the VY V6s were running,it could be programmed better to have more control of this problem.
The way it was done on the VY V6s was a stop-gap measure to comply with emission standards till the new engine was released imho.

Regarding the deletion of the dashpot on models with catalytic convertors,can you be more specific on what models did this??
The reason most of them deleted the dashpot with catalytic convertors was because they mostly had fuel injection .

They dont all do it mate, i drove my mates identical ute after i noticed mine playing up, and his drove normal, with the revs dropping off like they should.