where to start with erratic SPORT function/button?

[Goldsax]

2011 QP V GTS : the issue started last year, the sport button function worked for the first 30 mins and thereafter when pressed it would allow the function of the revs and gear change but had no function on the exhaust valves which were either left open or closed.
last week the sport button had no effect on then valves, but allowed the sport function on the gearbox and engine.
the valves are not seized.
I have read the threads re.this issue but should I start with.....a) change the rear solenoid b) fabricate a system that allows me to manually select valve function with a fob c) plug and play a Forza module that allows manual selection
any advice welcome.
thanks

 

[spkennyuk]

If you can get access under the car then i would pull one of the hoses off the exhaust valves and see if it is actually pulling a vacuum there first and work your way back up the line from there.

If its not pulling a vacuum there then go back to the solenoid and see if its pulling a vaccum there on the accumulator side of the valve. If it is then the solenoid is faulty or you have a leak on the exhaust valve side of the solenoid somewhere.

If there is no vaccum on the accumulator side of the solenoid then you will have to trace the pipe looking for splits back to the engine bay area and the accumulator tank. If the tank has any damage / hole / leak then the system wont work.

Obviously it needs to have the engine running and sport mode on to check the above. Not easy without access to a ramp.

If you want to add a fob activation option then @CatmanV2 did a diy upgrade on his GT for little money and a how to guide.

 

[Goldsax]

thanks for the guidance.
I will start this repair this weekend as a GTS is incomplete without its voice..

 

[Zep]

As that man said, it’s not the sport button, it’s almost certainly the vacuum system.

Perhaps one of these would help to test the actuator and a handy gauge to check for vac. Qnkaa Brake Bleeding Kit Vacuum Pump One Man Hand Held Fluid Bleeder Tool Tester Set With Gauge Adapters for Automotive Car Motorbike Motorcycle https://amzn.eu/d/ix8NTGG

Also check the wires to the actuator, that could also do it.

 

[CatmanV2]

I didn't weigh in because
a) There are better people and
b) This....

exhaust valves which were either left open or closed.

Which would seem to indicate either a mis report or possibly a stickiness in the solenoid, or intermittent failure to trigger it.

C

 

[Sam McGoo]

a GTS is incomplete without its voice..

That suggests its staying quiet when you press the sport button?

When you first start the car cold, does it start loud then go quiet a few seconds later?

The vacuum from the engine/accumulator builds up after first starting and the vacuum closes the valves making it 'Quiet'.
If from cold it starts quiet - the exhaust valves are sticking.
If it starts loud, then goes quiet and you can see the valves move closed- the valves and the vacuum system is working. If the Sport button doesn't make it go loud again, then it'll be the solenoid, either a blocked vent (unlikely), sticky solenoid or the electrical signal to it.

OR

If its suck in 'Loud' and the exhaust valves can easily be moved by hand, you've almost certainly got a vacuum leak between the accumulator and the Valves (normally either the hose off one of the valves, or its holed behind the drivers side front wheel arch liner, but again could possibly a faulty solenoid.

 

[Goldsax]

yes. car starts loud and then stays quite.
therefore, it looks like its not a leak issue, but a solenoid or signal to solenoid issue.
I'll get a multimeter to the wire today and hopefully get a diagnosis

many thanks to all that have replied and helped.