Idle speed control extreme value on a cylinder, AFB?

Hello everyone!

Perhaps I should elaborate more when describing the question...
'For some time now, I've had the feeling that my engine is making a knocking sound, even when it's warm. Because the Audi A6's engine bay is quite well insulated, you really have to listen closely to hear it. However, you can clearly hear a knocking noise during acceleration. Of course, it's much more noticeable when the engine is cold. I suspect that since the sound only occurs when accelerating, it's not likely to be valve clearance or a bearing issue.'So, I finally pulled out the cable and VAGCOM again after a long time. The injection start timing at idle and under full load were within the normal range, as set by the EDC control unit. So, it probably isn't related to that?
'Just for fun, I disconnected the NHG (presumably a sensor or module). What's surprising is that the error immediately appeared in the fault memory, but the EDC (Electronic Diesel Control) didn't go into emergency mode... at least, the warning light didn't flash *amazing*. Also, while driving, there was no noticeable significant loss of power. *even more amazing*.'
Mit wieder angeschlossenem NHG schaute ich mal bei den Werten der Leerlaufruheregelung. Dort sieht die Sache meiner Meinung nach nicht so schön aus... da es ja ein 6 Zylinder ist, werden auch 5 Werte angezeigt. Drei Werte bewegen sich im Bereich +/- 0,5 einer hat um die +0,9 und der letzte bringt einen Wert von -1,8 bis zu -2,5. Dieser Minuswert bedeutet doch, das weniger Diesel in diesen Zylinder eingespritzt wird!? Ist die Abweichung nicht etwas zu groß?? In another post about the hole in the piston, Ulf wrote that this could possibly be a sign of a leaking injector!
Now, the most important question: Does anyone have any idea whether something can be done about this, and if so, what? Would it be enough to simply replace that one nozzle?

Brief profile:
- AFB engine, manufactured in 1998.
- no biodiesel
- no chip
- 172,000 km mileage / distance traveled.
- 20-30% short distances.
- 1. Nozzle set.

Thank you for your help and have a nice Sunday!

DENNIS

Hi Dennis,

I want to take some of the writing work off Bertil's hands ( ).

I would replace the nozzles (at least the NHG ones) given this mileage . The risk of a stuck needle is not worth the price of the NHG! Take a look on eBay... sometimes you can find new nozzle sets at fair prices! Otherwise, I can recommend Boller and Co in Wiesbaden for brake parts: 0611-422031.

P.S.: My Passat is running like new again . Cause: incorrectly adjusted fuel injection start and a misadjusted quantity control valve .

Hi,

haehnlein wrote:

...I want to take some of the writing work away from Bertil ( ): ...

Thank you, then I don't have to strain my fingers writing anymore...

Quote:

I would replace the nozzles (at least the NHG ones) with this mileage . The risk of a needle seizing is not worth the price of the NHG!

... I completely agree.

GarfieldMZ wrote:

Hi. Mit wieder angeschlossenem NHG schaute ich mal bei den Werten der Leerlaufruheregelung. Dort sieht die Sache meiner Meinung nach nicht so schön aus... da es ja ein 6 Zylinder ist, werden auch 5 Werte angezeigt. Drei Werte bewegen sich im Bereich +/- 0,5 einer hat um die +0,9 und der letzte bringt einen Wert von -1,8 bis zu -2,5. Dieser Minuswert bedeutet doch, das weniger Diesel in diesen Zylinder eingespritzt wird!? Ist die Abweichung nicht etwas zu groß?? In another entry concerning the hole in the piston, Ulf wrote that this could possibly be a sign of a leaking injector.

Hi Dennis,

My previous post is currently just speculation, but as far as I know, none of the "pump experts" have contradicted it yet – which suggests that the story is at least plausible.

What is the typical fuel injection amount displayed by VAGCOM in the normal idle group?

Hello!

Thank you for the quick responses!

'@Ulf: I'll check the idle speed tomorrow and post it here.'

@haehnlein: Have you ever looked at how much the NHG costs? As far as I remember, Audi wants at least 250 euros for that part . Unfortunately, I've never seen any nozzles for mine on eBay. It's always just nozzles for the 1.9 or the 5-cylinder 2.5 engines.

What I don't know right now is whether the nozzle with the -2.5 value also corresponds to the NHG type... I'll check which cylinder has this value. Then, I just need to figure out how the cylinders are numbered in the V6 engine .

Is it possible that this nozzle, with its high pressure, is also responsible for the nail formation? What exactly is meant by the term 'nozzle nailing'?

Unfortunately, a partial replacement on the V6 engine is not that simple because the injectors pass through the valve cover. This means you always have to remove the valve cover to remove the injector .

Regards,

DENNIS

GarfieldMZ wrote:

Have you ever looked at how much an NHG costs!? As far as I remember, Audi wants at least 250 euros for the part . Unfortunately, I've never seen any injectors for mine on eBay. Always just ones for the 1.9 or the 5-cylinder 2.5

.

Hi Dennis,

I only know the price for the 1Z: 127 euros for a replacement unit... At VW, these things also cost over 200 euros, so I suspect that your NHG (New High Quality) part for the Boller is not much more expensive .

Hello!

'@Ulf: The idle fuel consumption fluctuates between approximately 5.6 mg/H and 6 mg/H. VAGCOM apparently doesn't display any values in between. I'm assuming it averages around 5.8 mg/H. According to my information, this is well within the normal range (3 - 8 mg/H).'

I have now also obtained the individual correction values. At a temperature of 88°, the following values apply:

Cylinder 3 to Cylinder 2 = 0 mg/hour.
Cylinder 1 to Cylinder 2 = +0.1 mg/hour.
Cylinder 6 to cylinder 2 = -2.0 mg/h.
Cylinder 4 to Cylinder 2 = -0.5 mg/hour.
Cylinder 5 to cylinder 2 = +0.5 mg/hour.

As you can clearly see, cylinder 6 is significantly deviating from the norm. This is what's causing me concern, and it might also be the reason for the (in my opinion) excessively loud knocking sound. The values are not very consistent and vary by +/- 0.2mg/H. The readings from cylinder 6 sometimes range from -1.7 to -2.4. If I'm not mistaken, at an idle fuel injection rate of 5.8mg/H, cylinder 6 might only be receiving a little more than half the amount in extreme cases.

Then I'll wait to see what the injection and nozzle experts have to say about it .

Thank you in advance!

DENNIS

GarfieldMZ wrote:

As you can clearly see, cylinder 6 is sticking out quite a bit.

This is what's causing me concern, and it might also be the reason for the (in my opinion) excessively loud knocking sounds.

Hi Dennis,

To me, it looks like a problem with the injectors, because if only 50% of the normal fuel injection amount were being delivered to one cylinder, the engine probably wouldn't run smoothly.

"Knocking" can also be caused by this: the injection starts before the ignition temperature is reached, and then everything that's already in the cylinder ignites suddenly -> resulting in knocking."

If the pump experts say something different, that naturally takes precedence }.

@everyone

I read somewhere that you can sometimes free up clogged or partially blocked fuel injectors (meaning injectors that aren't working perfectly) by adding about 2.5 liters of motor oil to a tank of gasoline. What do you think about this? Wouldn't it just be a temporary fix until the injectors are properly cleaned or repaired?

joergs wrote:

I read somewhere that you can free up and unclog

injectors (meaning, injectors that aren't working perfectly) by adding about 2.5 liters of motor oil to a tank of fuel. What do you think of this? Wouldn't it just be a temporary fix until the injectors stop sealing or opening properly again?

Hi Jörg,

"For that to work, the oil would likely need to have some cleaning properties to remove any residue causing clogs in the nozzles."
Or, at this low concentration (!), somehow lubricate better than diesel, but that would decrease with each refueling. . .

Neither of them seems immediately "logical" to me.
However, some well-established practical experience is also not very logical }.

@ulf

I consulted with another experienced mechanic again. He mentioned that this technology ('through-going success') had been successful in older diesel and turbodiesel engines. TDI? Unfortunately, I don't know enough about the differences in injectors to comment on that! I just wanted to bring it up for discussion.

joergs wrote:

I consulted with another experienced mechanic again. He mentioned that this method had "remarkable success" with older diesel and turbodiesel engines. TDI? Unfortunately, I don't know enough about the nozzle differences to comment on that! I just wanted to bring it up for discussion!

Hi Jörg,

That's what a forum is for, after all .

Maybe Dennis will try it out sometime, then we'll know more (although a positive result would be difficult to explain, in my opinion...).

Hello!

I've never heard of that with motor oil. You can try it, I guess, but somehow I have a slightly uneasy feeling about it when it comes to my machine. Moreover, it can quickly become quite expensive if any side effects occur.
Such a thing as an AFB costs quite a bit .
I might (as a mechanic friend suggested to me) try the good old Liqui-Moly. I don't have much hope for success with it either, but this method probably has fewer drawbacks than using oil .

Perhaps someone could try it out beforehand with the oil on a small 1Z engine .

Regards,
DENNIS

How about your camshafts? If they are worn, the engine might also be making more noise than usual. I'm speaking from experience. Mine has now reached 155,000 km, and after replacing the camshafts at 135,000 km, it runs like a new one.

One of my nozzles also has a value of approximately 1.5, while all the others are around +/- 0.5. I don't think that's necessarily bad.

Perhaps he has found a solution. But perhaps he won't even drive the car anymore after 3.5 years.

Oops .

Thank you for the information.