snagitseven

Just to clarify, the extended warranty to 10y/120K miles for certain year 3.2 and 3.0T engines is for the secondary air ports only (located lower down in the cylinders where fuel ignitions don't reach) and a CEL must be evident for coverage. The extended warranty does not cover any other carbon build up issues including the valves, etc. My letter from AoA clearly specifies this.

DennisMitchell

But a CPO extended warranty should cover it. Right? I wonder because this is not a failure of a specific warranty covered part. It is a condition developed because of the design that makes the engine not perform properly.

snagitseven

Should cover what? The secondary air ports? Yes, but the 10y/120K extended warranty would supercede any other warranty anyway. If you mean carbon deposits on other areas of the engine including the valves, then I believe Audi would not normally cover cleaning deposits under either the standard or a CPO warranty. They would claim other causes, i.e.not using Top Tier gas or whatever. The SAPs can't self clean due to the design, therefore Audi felt they had to address it with the special extended warranty.

ELEVENS

This comes up all the time and I'm afraid that's little more than snake oil. My personal experience with post-IS teardown and inspection, along with others who have done the same, is that it simply isn't at all effective at removing the baked-on coked carbon that collects on the intake valves. I'm a chemist by trade, and have done 3 teardowns and cleanings. I have tried all types of solvents from my lab to accelerate the manual scraping, including a half dozen automotive solvents specifically designed for IS cleaning. I've even used a laboratory sonic dismembrator with solvents on the valves and intake ports. Nothing I've tried works half as good as gasoline to help soften the coke. That coke might as well be ceramic or diamond-type carbon. Solvents are rather ineffective at dissolving it. Please don't try anything flammable like gasoline at home!

As an experiment, I've introduced a pint of gasoline aspirated into a running motor (via a special vacuum port) dozens of time over the course of a few months, tore it down for inspection, and what I found was that the gasoline was marginally effective at (slightly) reducing the coke, but the distribution pattern was uneven, with the cylinders closest to the vacuum port receiving the most effect, and the cylinders farthest received nothing. The commercial IS equipment (BG sells one, a fellow RS4 owner bought one and thoroughly tested it, then immediately SOLD it because it was ineffective) uses pressure instead of vacuum to introduce solvent which theoretically may aid distribution, but even 100 times nothing is still nothing, if you get my drift.

I'll say it again: there's no need to worry about carbon on the intake valves, other than a minor performance hit. The real carbon issue with the 3.2 Q5 is carbon in the secondary air exhaust ports, which must be cleaned by either engine removal, or more recently, special Audi service equipment designed specifically for the job. The attached pic is from my RS4 at around 35,000 miles.

Sigq5

Elevens just laid out a great explanation on subject. It supports points made by others o where the CB issues are worst
I would welcome responses on the following items
1- is CB an issue for normally aspirated engines
2- are turbo charged or supercharged engines experiencing CB
3- are Diesel engines vulnerable to CB
Look forward to response

raj99

Hi Sig,

I wrote about the CB here awhile back: https://www.audiworld.com/forums/a6-.../#post24493861

But here's the entire text for those, who aren't inclined to follow the link:

So all C6 3.2 engines are DI (Audi calls is a FSI), they are the first OEM to make ALL their engines this way. DI is really great for making the fuel/air mix ratios and concentrations perfect, it takes less fuel to make the right mix with DI, it takes less fuel to get the same power using DI, and it can also fight knock (pre-ignition, which harms engines) since every injector can operate independently – allowing the ECU to control the fuel to every cylinder individually. It is also used if the engine gets too hot and the coolant cannot keep up by purposefully putting extra fuel in which will evaporate harmlessly but take heat with it. Here comes the con(s).

Non-DI engines have the injectors in the intake channels, and spray the intake valve’s backing as it opens into the cylinder. This happens with each intake stroke, “washing” the intake valve with fuel. You have, I am sure, seen the Chevron with Techron and like commercials about it having additives which keep valves clean. This is great for NON-DI engines. Why the valves need cleaning is due to 1970’s legislation to handle pollution. Exhaust Gas Recirculation (EGR) and Positive Crankcase Ventilation (PCV) are 2 things required by law in the US (and many other countries) to prevent pollution. EGR pipes unburned fuel and particles in the exhaust, back into the crankcase to prevent catalytic convertor congestion and failure (things like unburned fuel, impurities in the fuel, water vapor, CO2, and oil). PCV takes crankcase vapors (mainly just oil particles and the EGR stuff) which is under pressure and pre-1970’s was just vented to the atmosphere, but now is redirected through a valve system which has a rough collection system that attempts to pull the largest particles from the air in this, and separate them out and allow them to drip down into the oil filter to be collected (if bad) or allowed to be cleaned and returned to the oil pan for engine lubrication – the particles too small to collect are mixed with fresh air coming into the engine just above the intake valves and shot back into the engine to attempt to re-burn them properly.

As you can imagine, the particles will collect on all parts of the intake, turning into sludge eventually and oozing into the intake, where it eventually is burned away during combustion. The problem happens with DI engines – the injectors shoot fuel DIRECTLY into the cylinders and don’t wash this gunk off the back of the intake valves. As such the gunk builds up here but since it’s so close to the cylinder, the heat bakes the gunk into carbon deposits which build up slowly over time. These deposits eventually become so heavy that they affect the airflow into the cylinders, making them move in unexpected patterns, or in very bad cases, not enough air is pulled in as the ECU is expecting, either way the result is too much fuel to the air ratio, or uneven mixing of the fuel, which robs engine power, can cause rough idle, and eventually cause Check Engine Lights (CEL’s) due to misfires (especially when the engine is cold). This causes a negative spiral, where the even higher amounts of unburned fuel due to the Carbon Build-up (CB) makes even more unburned fuel be re-circulated and these richer deposits speed the buildup on the backs of the valves further.

Things that affect this are:
- Fuel quality: The crappier the fuel, the more impurities and the more likely there are to be deposits to collect
- Driving distance/engine temps: Those hit hardest are short distance driving, where the engine never gets up to temp. Getting the engine hot means that the gunk won’t be able to collect as readily, because it’s baked off by the high temps.
- Poor seating of the cylinder rings: More oil seeps by into the fuel adding to the large amounts of particles recirculated into the intakes. Use of more than 1Qt of oil every 5K miles means higher than average oil consumption usually meaning poorly seated rings, causing excessive blow-by.

A few things are done by people to correct this.
- Carbon Cleaning – the top of the engine is pulled apart, intakes and valve covers are pulled, and the heads removed, then a Dremel or similar tool is used with a fine grain grinding bit are used to grind the carbon off the intake runners, the intake air flaps, and the backs of the valves. This is usually done around every 20-30K miles by those wanting to be sure they have the power and performance of the car unaffected.
- Catch Can – This is a 3rd party development, which partially bypasses the EPA mandated pollution measures mentioned above. It basically goes in-line with the recirculation of the gases before they hit the intake, comprising of a separate filter system that more aggressively captures and holds the particles the stock system doesn’t handle. The difference here is that the aftermarket solution doesn’t drop this into the oil, it holds it in the can, and you have a drain at the bottom where every 5-7K miles it needs emptying. Due to this being “bad stuff” from inside the engine, it cannot be disposed of easily, and is best poured into old oil containers and taken to a recycling place like Schuck’s or your local recycling transfer station, it’s mainly oil, water and fuel, so it can go into oil recycling.
- Methanol Injection – Typically referred to as “Meth” it’s been around a LOT longer than the illicit drug, and is basically a raw form of octane. What it’s used for is to both cool the incoming air (making it denser and therefore holds more oxygen for combustion) as well as boost the octane rating, which equates to more power. Methanol is mixed 50/50 with distilled water, and uses a special tank to hold it in, with its own pump and delivery system. The methanol is injected into the air intake around the throttle body, misting the incoming air. The methanol mist in the air cools it through evaporation, and since it’s a combustible liquid, it helps take place of the washing that non-DI engines get, by coating the backs of the valves and pulls the deposits into the fuel system rather than it baking and hardening there, as well as giving more horsepower and performance out of the car at the same time. Methanol is not very expensive, but is dangerous due to high octane and ability to burn, hence mixing 50/50. A typical use system will go through a small (1 liter) tank every 1-2 tanks of gas.

One of the things I didn’t mention (as it didn’t pertain to your car) is that Forced Induction (FI) engines are not as susceptible to this, the reason being the much higher compression and thus higher cylinder and valve temps if you do get it out and run it for at least 10-20 minutes at normal running temps.

Sigq5

Getting an education from you guys.
Do you think that turbocharged or supercharged engines are vulnerable to CB
How about TDI, how vulnerable are they to CB?
Thx in advanced.

Bad Andy

Not all 3.2 engines have this problem. Mine has 177,000 miles on it and I have never had a CEL.

amkmeco90

The first time I did that CB cleaning was when i reached 30,000 miles. About a week ago, less than 200 miles from reaching the warranty end point at 100,000 miles, I got CEL on and was confirmed to be CB. It will be covered under warranty but was found that the injectors need to be cleaned besides this. They will only charge me for cleaning those injectors about $300. My car is an 09 Q5 3.2 and my driving is 50/50 city/hwy. I usually use those Techron fuel injector cleaners but seems like they are of no use. That seems to be a chronic problem with no permanent fix and just waiting to happen at any time.

AprilBaby

I am having trouble getting my extended warranty to cover this repair. My car is over 120K miles and Audi will no longer cover the repair. What should I do to have the extended (bumper-to-bumper) warranty cover this repair?