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VT wont rev past 4.5k

ohwow

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Hi everyone. I own a 1998 VT Commodore (S1). Ever since I've owned it, its done this. Its an intermittent problem, sometimes it will run perfectly when WOT and doesn't get stuck but lately its doing it more often than not.

I've attached a shaky video (apologies) to show the issue:


In search of a resolution to the issue I have replaced the following:
Leads,
Spark plugs,
Fuel Filter,
Transmission flush + fluid replacement
Transmission filter


I have also checked/cleaned the following:
Checked Cat for blockage (all clear)
Checked and cleaned MAF
Checked and cleaned throttle body
Checked for vacuum leaks (nothing)

I have had a Tech II scan and the only code that came up was for the ABS (which this vehicle is not fitted with)

So I'm kind of lost now.. I've searched around and I cant find anyone else with this issue.
Only things I can really think of now would be the O2 sensors, coils and fuel pump.

Other than this problem, the car runs perfectly. When not driving WOT the thing has no issues changing and fuel economy is as you'd expect for any V6 VT Commodore.


Any ideas?
 
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acarmody

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Air or fuel filters changed?
 

ohwow

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Yep fuel filter more recently than air filter but both have been changed well after this problem began.
 

Big-Al

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Is the transmission shifting down a gear when you step on the throttle? I'm wondering if the throttle position sensor is stuffed as it seems to change up gears before redline?
 

chargedvx6

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Fuel pump or abs module
 

oska

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it's a safety feature the engine won't rev past 4.5K until it reaches operating temp

maybe the thermostat has been removed or an incorrect one fitted
 

ohwow

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it's a safety feature the engine won't rev past 4.5K until it reaches operating temp

maybe the thermostat has been removed or an incorrect one fitted
It tends to run at about 74c when driving. Only time it changes is when its idling. When idling it will hit about 103c then the fans will kick in bringing it back down to about 95c
 

ohwow

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Is the transmission shifting down a gear when you step on the throttle? I'm wondering if the throttle position sensor is stuffed as it seems to change up gears before redline?
Yeah it does. In the video when it changes up a gear is when I let off the throttle.
 

oska

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92 degree is the operating temp

i would check if the thermostat
 

theghostoftime1978

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does it rev past 4.5k in park or neutal?, how many kms? and was that full throttle as well? it seems to take forever to get to 100km/h as well, disconnect the battery for half an hour and see if that resets computer. looks like its running in limp home mode
 
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