Loss of Top end power - V6 Auto

[Nick C]

Hello Lads,

I have a problem with my 2004 VY V6 Auto

Basically I have noticed a decrease in power in the higher rpm. 0-100 time is 8.1 seconds and it struggles to get past 180km/h

I have dragged bone stock commodores and we are always head to head.

The car has done 270,000km
The car does have mods and the following done.

New Iridium Plugs (NGK)
New 9mm leads (ICE)
New High Voltage Coils (Mace)
Bored 69mm Throttle Body (Mace)
Plenum Spacer 12mm (Mace)
Manifold Insulator 25mm (Mace)
Mace tune for 98 oct
Pacemaker headers
Stock Centre Muffler and straight pipe out the back.
Cats removed
Ryco Peformance Filter. (Plenty of air flow)
Oil change (ryco filter and Penrite 10w40)
Coolant flush and fresh coolant
Trans service (filter change)
Diff fluid changed
Brake fluid changed
Intake manifold gasket replaced
Maf Cleaned and intake manifold


I am absolutely stumped to why I have lost power and I done so many checks and testing and I can’t find the problem.

Using tuner pro, the O2 sensors are telling me the car is running rich and lean back and forth even at idle.
When idling the car every 2 mins or so will increase idle to 1500rpm and suddenly drop back down slowly

With the upgrades there I definitely and increase in torque.

Any help would be appreciated!

Thanks Team

 

[harrop.senator]

I can't really help as I don't usually bother going over 120 in a V6 commodore.

Have you done a compression check? What's the knock sensors reading up high it's not hitting rich and retard? Why you using the crappy mace memcal if you've got tunerpro capabilities?

 

[Nick C]

Compression came back good. O2 sensors change from rich the lean constantly. Knocks sensors nothing wrong. It’s a new ECU that mace sent me to comply with the bigger TB

 

[_R_J_K_]

It’s a new ECU that mace sent me

You got the old one you can throw in and test with?

 

[Nick C]

Yes - I still have it. Tested it and no change little worse tbh .

 

[Heavy VT]

Fuel pressure?
Fuel filter?

 

[Nick C]

Fuel filter has been changed.
How do you check pressure on this motor?

 

[Nick C]

Fuel pressure?
Fuel filter?

Fuel filter has been changed.
How do you check pressure on this motor?

 

[Heavy VT]

You will need a gauge and adapter hose that will clip inline where the hose clips onto the fuel rail on the engine.
Then you will need to test drive under full load at high rpm and see what the pressure is doing at that time.

 

[Nick C]

You will need a gauge and adapter hose that will clip inline where the hose clips onto the fuel rail on the engine.
Then you will need to test drive under full load at high rpm and see what the pressure is doing at that time.

I will give that a try - Cheers