Holden Commodore Problems

I would suggest that there was a misunderstanding on the part of the person who told you it could be done after delivery, but you should be able to have a dealer accessory, or an aftermarket system fitted.

The hard covers are made by outside vendors and supplied to the carmakers, like many hundreds, even thousands of parts that go into the cars we drive. They are supplied to the specifications of the carmaker and the carmakers check them to ensure they meet the specifications. They assess the likely impact of each part on the car's crash performance and decide what they will submit to ANCAP for testing.

What you bought is an old car, and old cars are often worn out, so what you’ve replaced is not to be unexpected. You’re so far into it that it’s best to keep going rather than pull out and lose what you’ve put into it, particularly because it’s an SL/E, which will be worth more than a regular old Commodore when you’ve finished it. The ultimate decision on how much to invest in the car should be based on the condition of the body and interior. If all of that’s in good condition it would be worth spending the money you’re spending, but if it’s rusty or needs repairs to the panel work I would suggest you think about getting out of it.

It’s impossible to say, but I would err towards the GPS. It’s most unusual for a speedo to read higher than the real speed, it’s usually the other way around. I would crosscheck the GPS on another car.

It’s going lean for some reason and not getting the enrichment it needs to accelerate. Check the throttle body.

I would expect your car to return around 11.0 L/100 km, so yours is very poor as you say. You would have to allow for slightly higher fuel consumption due to wear on the engine, loss of compression etc., but I would still expect that you should get around 12 L/100 km. I would be checking the basics, like spark plugs, spark plug leads, air filters, fuel-injectors, and throttle body to make sure they are all in tip-top shape; then look at sensors like the oxygen sensor to make sure they are conveying the correct signal to the engine computer.

Many thousands of V6 Commodores have been successfully converted and there’s no reason to be afraid of converting your car. It would be fitted with an old style of system rather a new injection type, but there’s nothing wrong with that. A word of caution, however, is that you should make sure your engine is good and healthy before you convert it. It’s an old engine and I’m guessing it’s done lots of kays, so it’s worth having it thoroughly checked for tune and compression before you commit to the conversion.

The hard covers are made by outside vendors and supplied to the carmakers, like many hundreds, even thousands of parts that go into the cars we drive. They are supplied to the specifications of the carmaker and the carmakers check them to ensure they meet the specifications. They assess the likely impact of each part on the car's crash performance and decide what they will submit to ANCAP for testing.

I would have the wheels and tyres balanced, then start looking at rear suspension bushes and drive shafts.

If you feel it is a problem, and the presence of piston slap is not necessarily a problem in itself, you should keep meticulous records of your dealings with the dealer and Holden in case it does escalate into an issue that needs addressing. In that case you would be well armed with the information needed to support your case for Holden to act.