VP running rough when at operating temperature..

[firefox45]

Hi folks,
My VP runs fine when I first start in the morning when it is still cold. But once it gets to operating temperature, it starts to run really rough when I accelerate. It coughs and splutters generally lacks power when I accelerate.

So far I have replaced the coil base and packs, spark plugs, leads and the oxygen sensor but the problem still remains. My son and I did the the self computer diagnostics with a paper clip as described in the How To and the code comes up as 12 every time (no faults by the codes sheet).

I'm wondering if anyone has any idea of what might be causing this. Any suggestion would be greatfully welcomed. We are at a loss as to what may be the problem.

All the best
Firefox45

[levymetal]

even without error codes, i would try checking the CAS (Crank Angle Sensor) first. put a bottle of water in the fridge, then start your car up/take it for a drive to get it warmed up. when it starts playing up, pour some nice icy cold water behind the balancer (that's where the CAS is). if the problem goes away temporarily, you know what to fix

[aussieghostrider]

yeah the Crank Angle Sensor is a pain in the ass .... they can cause bad idle , stalling , then finally dies car wont start at all ..

as mentioned .. next time it happens pour cold icy water over the CAS whilst engines running to see if theres any change ...

If its not that then when was the inlet manifold gasket replaced last ??? engine heats up and theres pressure in cooling system and water gets into cyclingers and causes a miss, bad idle , stalling and it will get worse and worse ...

If you flush cooling system .. and put bottle of CARGO stop leak from repco ... leave it in for few days ... then drain water and leave dry for 12 hours ... then put coolant in it and see if that helps .. if it does then you know where the problem is ..


if not ...

[firefox45]

Thanks for the advice,
we tried the cold water on the crank angle sensor when warm and it still was running rough. So we'll try the Cargo Stop Leak soon to see if that makes a difference. We'll keep you posted as to what happens.

Once again, thanks for your advice.

[KnobMuffin]

When the car is cold the computer runs a much richer mixture (more fuel is sprayed into the cylinders) however when the car heats up the computer runs a leaner mixture (less fuel is sprayed) so perhaps something is going wrong in the fuel system. Basic things you can do without spending money, check the fuel pressure regulator for correct operation and check your injectors for the correct resistance. Also check the coolant temp sensor for the ECU. I dont have the specs with me on this computer but you can search these forums and I am sure you will find them. It sounds like something is going wrong when the computer tries to run a leaner mixture.

[firefox45]

yeah the Crank Angle Sensor is a pain in the ass .... they can cause bad idle , stalling , then finally dies car wont start at all ..

as mentioned .. next time it happens pour cold icy water over the CAS whilst engines running to see if theres any change ...

If its not that then when was the inlet manifold gasket replaced last ??? engine heats up and theres pressure in cooling system and water gets into cyclingers and causes a miss, bad idle , stalling and it will get worse and worse ...

If you flush cooling system .. and put bottle of CARGO stop leak from repco ... leave it in for few days ... then drain water and leave dry for 12 hours ... then put coolant in it and see if that helps .. if it does then you know where the problem is ..


if not ...

Well, we put some of the Cargo Stop Leak in after we flushed the coolant out like aussieghostrider was saying. The car seems to not be running fine now. This is after a couple of hours of running, so we're thinking that it may be the inlet manifold like you were saying. We'll leave it in for a few days and let it dry then replace the coolant. So thanks aussieghostrider and other folks for your advice. Also thanks to justcommodores for such a great web site.

all the best firefox45

[aussieghostrider]

if you put cargo stop leak in make sure you have no green coloring in the water when you add it ..

the stuff wont work if theres green coolant in system ...

You need to get engine to warm up so it sits half way on temp gauge ... this ensures the gasket expands as much as it can and the pressure in system should force that cargo stuff up where inlet manifold seal is and slow the leak or if your luck stop it ..

you need to go on a freeway or something to ensure the stuff works it way thru the system ...

I ended up putting 3 bottles of the stuff in over a few weeks ... then drained system and let it sit dry for 12 hours ... then added coolant again ... and it helped alot ...

before putting any more bottles in make sure you have really flushed the system well ..

[hi_ryder]

had the same problem with my vp calais, paradox and i did the inlet manifold gaskets yesterday and still have the same problem. the inlet gaskets were stuffed and needed to be done anyway, but the car is still losing power when the temp gets between a quarter and half on the temp gauge. if i give it a good dose it even back fires (well sounds like a back fire) sounds like the exhaust is chocking. could this be the CAS or should i explore the fuel side...