Fuel Additives & Decarb for petrol engines?

[3C4M Guy]

I've been using a 90 ml can of VAG Multipurpose Additive for petrol G 001 770 A2 about every 3 months to help clean the injectors and valves. Can't feel any difference but hopefully it's doing some good.

However what about decarbon? Does anyone know if VW recommend the use of a product that is sprayed into the intake to remove built up carbon deposits? There's a Liqui Moly Intake Decarb. Maybe there's a genuine VAG product? Don't want to use anything that might do any harm.

[Umai Naa!!]

I cannot recommend the Liqui Moly intake cleaner highly enough.

Does wonders for the direct injection motors. Pretty much every R36 I service, gets a can of it.

[3C4M Guy]

I cannot recommend the Liqui Moly intake cleaner highly enough.

Does wonders for the direct injection motors. Pretty much every R36 I service, gets a can of it.

Thanks Umai Naa!! That's great to know. What's the procedure for using it? Do you remove plastic intake before the throttle body and squirt in there? The product looks like it's supplied with a long plastic tube for getting right into the intake manifold.

[Umai Naa!!]

I slip the hose clamp back along the intake pipe, where it's secured to the MAF, and push the tube in there. It's a snug enough fit that you don't need to put the clamp back on. It might draw in some unmetered air, but it's not really a big deal.

On these, you either need a longer hose, or a second person to rev the motor while you spray.

I try and hold it around 3,000rpm, and spray the can intermittantly. Maybe for a second, then wait til the revs stabilise, and spray again. Usually takes about 5 minutes to empty the can. Do it outside. What comes out the exhaust stinks.

Once it's done, check and clear the fault codes. You'll probably get a missfire code or two. Do a DSG reset, too. Then take it for a spirited drive. It'll feel like new again.

[3C4M Guy]

I really appreciate your detailed reply Umai Naa!! So you don't do the step where you spray into the intake manifold with the engine off and wait 2 - 3 minutes before starting the engine? I guess that could flood the intake so much it might be difficult to start? Or you might get more into one particular cylinder than the others?

When you insert the tube into the side of the intake pipe, do you feed the tube in a long way so it reaches the throttle body?

Regarding the DSG reset, there seems to be many values that can be reset: clutch safety function, pressure adaption, ESP & cruise control etc. Do you do them all? I don't want to lose my Harding Performance DSG tune!

[Umai Naa!!]

LM suggests to spray it into the intake pipe only. I would advise not getting too close to the throttle body. I only push it in under the pipe where it slips over the MAF, maybe an inch or so.

As you've said, I wouldn't pump the full can in with the engine off. While it's running at around 3,000RPM. It will be more evenly distributed to each cylinder, and the crud will be burnt off in the combustion process anyway.

As for the DSG reset, just do a basic reset. It's just key on (engine not running), with the accelerator to the floor for at least 10 seconds.