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Vs backfiring and running bad when hot

Michael vs

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Hey guys n gals if anyone could help me out here be much appreciated i own a vs series 2 executive i have this issue that when it gets to operating temp it starts to run a bit sad and every now and then it will backfire i have tryed everything to fix.My mechanic told me to take to a auto elec i took there he put a new crank angle sensor in for me 200 dollars later still have problem. I have changed myself,sparkplugs,leads,fuel pump,fuel filter,dfi module off a vt ,new coil packs i dont no what to do any suggestions would be great thanks
 

Immortality

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Are you using LPG?

One item you didn't mention was the Fuel Pressure Regulator. You might need to check the fuel pressures and make sure it's not leaning out or excessively rich.
 

Michael vs

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No lpg i have not checked myself yet thought my mecanic would have but will check and let you no how i go thanks immortality
 

greenacc

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TPS might be playing up they do strange things as the resistor wears out giving false throttle position to the ECU.
 

jesterhead

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Yup, what these guys said. But if it isn't your throttle sensor or pressure regulator, it could be a vacuum leak.
To check it, let it run at operating temperature. Check all your vacuum hoses for any perishing or cracks (there's
a couple of pain in the arse ones that are located under the plenum/intake runners, just so you know). If they're
all good, grab a length of garden hose or similar, about half a meter will do, put one end to your ear and the other
to the engine to listen for leaks (yes, I'm dead serious) around the plenum and intake-to-head areas.
If you do hear a leak, spray a bit of engine start in the area. If the revs go up, you've got a vacuum leak.
Let us know how you get on :)
 

Tonner Matt

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Replace the Cam Angle Sensor as you have changed just about everything else.
Had a VS ute that had the same symptoms you describe, this generally points to the CAS, so replaced the Crank Angle Sensor (CAS) and went for a drive, and as soon as it got to operating temp again the same problem reoccurred.
Scanned car for fault codes and got none showing up.
So knowing that all other parts were either new or in serviceable condition from being tested I replaced the Cam Angle Sensor and that fixed the problem.
 
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