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Curtis, Australia Car Mechanic
Category: Australia Car
Satisfied Customers: 1606
Experience:  Qualified Automotive Mechanic, LPG & Airconditioning Diagnostic Technician.
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I have a vz 190 kw eng its running rough at ilde and seem to

Customer Question

hi i have a vz 190 kw eng its running rough at ilde and seem to be idling to low i hav clean the crank sensor replace spark plug and manifold gasket clean map and air folw sensors but is still running bad but what i did notice the drivers side spark plugs were very black the outher side were fine at idle it is blowing black smoke out the exhaust it seems to running very rich what do you think ??
Submitted: 1 year ago.
Category: Australia Car
Expert:  Gary replied 1 year ago.

Hi there,

VZ V6 are known for many faults.

Have you done a compression test?

Have you scanned the vehicle for DTCs?


Customer: replied 1 year ago.
hi gary i havnt done a compression test its got 130 ks on it and its got no codes coming up some say it could be the timing chains but dont wont to go there at this stage pulled out the oxy sensor x4 last night driver side very sooted up pass side are fine
Expert:  Gary replied 1 year ago.

Ok, yes they are known for timing chain stretch, but if no codes are coming up, that could be promising.

I know it's a pain to remove the intake manifold for testing.

I would have the injectors cleaned and flow tested while you have the manifold off to do the compression test.

If you have valves not seating (only takes one cylinder) or a leaky injector, the whole bank will be sooty.

I had many engines that have suspect weepy valves, an upper cylinder clean then does rescue a lot of them.

Your carbon is generally from oil consumption.

Getting more common now on SIDI engines.


Customer: replied 1 year ago.
hi i put a decarbonizer threw the inlet and let it soak test drove the vehicle it runs ok out the road im thinking it could be a earth problem some where the customer has just told me he always seem to be blowing headliht globes and the fuel gauge plays up often . any idea ???
Expert:  Gary replied 1 year ago.

Hi again,

Check the grounds on the outside of the cylinder heads are tight.

And near the ABS module, chassis grounds.

Fuel gauge erratic could be a bad sender, or the start of an ECM failure, which is VERY common in VZ.

IF the vehicle ever has a no crank condition with fuel gauge error on the IPC, then the ECM is faulty.

For the headlight fault, I would also check the females of the headlight sockets, could be poor connection there too.


Customer: replied 1 year ago.
hi gary iv cleaned the earths done a compression test all at 150 cleaned pcv valve i took it out the road an fuel economy tells me it at 20 ltr to the 100 ks, at idle its a continuse cloud of black smoke coming from the exhaust iv cleaned the a f s and the sensor at the back of the inlet manfold mmmm maybe a fault afs ??
Expert:  Gary replied 1 year ago.

Hi again,

The AFS as you call it, is the MAF (mass air flow).

I would consider changing the MAF, cleaners don't work sometimes. I have seen many faulty MAFs.

Do you run a stock or oiled air filter?


Customer: replied 1 year ago.
hi gary i have replaced the maf and the sensor down the back of the inlet manifold no change to the car it runs a stock air filter it seems to be getting worse its blowing heaps of black smoke out the exhaust i still cant get any codes out of it im gunna take it to a shop in town and put his scan tool on it and hopfully tell me some thing hav you got any suggestions to try next
Expert:  Gary replied 1 year ago.

Hi again,

I would think the compression is low, but if they all at 150 psi, at least they are even.

Minimum spec is 140 psi. Perhaps you have an injector stuck open, (have seen this on many Holden products)

Some will stick partially open and be rich only, some will stick open and flood the engine, and even hydraulic lock the engine bending connecting rods.

Does the engine start normally, or have long crank time, and does it misfire straight after start up?

The early VZ were bad for not logging codes for misfire. VE are much better, different PCM.

A scan tool looking at O2 sensor data, before and after cats, MAF, MAP, ECT, IAT etc may reveal something.

20L/100 would be considered double average for VZ.