Allow me to enter into a "philospohical" discussion regarding pinging/knocking.

Vehicle: Audi 100, AAH, 2.8L, V6, 097 tranny, 10w 60 castrol edge engine oil, bosch spark plugs FR6D+, 110000kms on the clock (majority of it = short distance), 95 octane unleaded fuel, timing belt changed at 100000kms with major service.

This car is in perfect nick, except that it pings (for a short while)under load and on acceleration at top end (over 100 km per hour). It comfortably reaches highly illegal speeds although not as quikly as in the league of the RS4's of today.

I followed peoples' advice on this forum and others and local reliable mechanics and did the following:

1. Took the car to the dealership for a code test = not a single error code came up - they did not even charge for the test even after quoting R 350=00. They advised the change to 95 octane unleaded from lead replacement fuel which BTW is also 95 octane rated.

2. I used additives like Redex fuel injector cleaner (made it double concentrate)and took the car for long hard drive (about 80kms round trip)

3. Used Ultimoil compression stabiliser spray - removed spark plugs and sprayed it into cylinder, let it stand for a few hours, replaced spark plugs with new ones from bosch triode to bosch FR6D+. Started the car and as it was throttled I sprayed it into a vacuum line into the engine. Did this twice, one week apart.

4. Used W.Penn valve ease solution and Wynns valve guard lead replacment additive (both double concentrate).

5. Took the vehicle to nationally known company (Steve's AutoClinic) who specialise in performance vehicles for diagnostic - no fault codes found, did dyno run, fuel/air ratios and lots of other tests - NO CHARGE because they failed to identify the cause of the problem, They advised that I may try and get the car chipped (Dastek - Unichip) and that the local fuel may the problem.

Anyway the car still pings but still runs perfectly well.

My mech. says I need to live with it and change my driving style (ease back on throttle when it pings)'cos its carbon build up due to the previous owner using it on short distances (in 12 years it only did a 80 km trip once. otherwise its average daily distance was 10kms - all at low speed)

My question to all the engine gurus are the following:

1. Is there such a thing as normal pinging?
2. Does it actually mean that my knock sensors are working normally, because it only pings for a short while and then it goes away ie. timing is being retarded.
3. How bad does pinging have to be for it to be malignant and pathological to the engine ie. see question one.
4. What else can I do without having to send her in for "open heart surgery" (head removal) for something that may be a small problem requiring a simple solution.

Please advise further.

Regards
aadil
P. S. Sorry for the lengthy post, but I'm at my wits end now.

 

Did it ping before your timing belt service?

 

Why are you using such thick oil? 10w60?

 

Did you replace the thermo when you did the timing belt? Too hot and you get pre-ignition.

 

Hi there Gents,

Thanx for the speedy reply.

Now that I'm registered you guys will find me a regular contributor (at whatever level - I'm a health proffessional by proffession so wether my input is worth it with respect to cars, I'm not sure!!)

Did you change the Thermo?
Yes I did, but not with one from the agents (Pirate part). The car definitely pings when it is hot. It runs at a temperature of 90Deg Celcius on highway and 100 Deg celcius on stop start and idleing in traffic.

Why such thick oil?
When I got the car, I was still "wet behind the ears" (I'm actually a Golf MK1 driver all my life and I'm still getting used to the Audi feeling), I did what my mech told me!! I have changed now though - Can you suggets anything? Here in SA we don't have any weather extremes. It stays between 20-30 degrees celcius all year round.

Did the pinging start after timing belt?
Yup! but we also had a fuel octane change here in SA at the exact same time - from 97octane leaded to 95octane unleaded available only.

However, I brought this up with my mech. and he said that if the timing belt was done incorrectly (he did it BTW), I'd have a lot of other running problems as well, or that the car would not have even started because of the TDC sensors picking up a problem.

I was not even advised of replacing the water pump when I did the T belt. I only learned that after getting onto this forum.

Regards
aadil from SA

 

run seafoam through it, that should get rid of the carbon buildup.