VR6 Misfire: AYL, Sharan - Cylinder 1, 3, 5

Hello.

It's a Sharan BJ (model) from 2002 that has an unstable idle speed when running on gasoline.
Engine code: AYL.
Gasoline VR6.
Automatic.
with the Prins LPG system.
Gas control unit: ECM VSI 8.
LPG 67R


The following errors were stored in the error memory.

Address 01: Engine Control Module.
Control unit part number: 022 906 032 AR.
Component and/or version: MOTRONIC ME7.1 G 0005.


3 error codes found:

16684 - Misfire detected.
P0300 - 35-00 - -
16685 - Cylinder 1: Misfire detected.
P0301 - 35-00 - -
16687 - Cylinder 3: Misfire detected.
P0303 - 35-00 - -

Readiness: 0110 1101

First, I used VCDS to check the values related to misfire detection, and here's what I saw:
Measurement time: approximately 1-5 minutes in idle mode.
Cyl 1 = 28
Cyl 2 = 0
Cyl 3 = 208
Cylinder 4 = 0.
Cyl 5 = 4

Now, we have also performed a compression test.
Cyl1 = 12 bar.
Cyl2 = 12.9 bar
Cyl3 = 12 bar.
Cyl4 = 13 bar.
Cyl5 = 12.2 bar.
Cyl6 = 13 bar.

To rule out a possible fault with the Prins gas system, I have...
The original cable connections from the control unit (STG) to the electric valve were reconnected, but no change was observed.

Then I swapped the injectors from cylinder 1 with those from cylinder 2, and from cylinder 3 with those from cylinder 4, and from cylinder 5 with those from cylinder 6.
And the errors have now been corrected.
Now, cylinders 2, 4, and 6 are experiencing misfires.

All 6 cable connections from the control unit to the fuel injectors were checked for continuity using a multimeter.
The average values are 0.3-0.4 Ohms, including the resistance of the measurement leads.
The voltage supply (on the positive side) to the valves was also checked.

The three fuel injectors need to be replaced now.

My question is:

Are these potential consequences of a faulty VSI control unit, even though the engine runs smoothly when operating on gasoline?
or
Is there a defect in the power lines that may not be delivering enough current under load?

Are there any gear-shifting relationships between cylinders 1, 3, and 5 controlled by the engine control unit?

Hello candidate!

Prüfling wrote:

... Are there any switching-related connections between cylinders 1, 3, and 5 from the engine control unit (ECU)?

Using logic, one could even argue that the question itself is irrelevant and therefore doesn't require an answer.

Since the misfires are now occurring during the injector replacement process, it cannot be due to either the wiring/connectors or the engine control unit (ECU)!
Okay, let's assume that you didn't leave anything else "along for the ride" besides the fuel injectors themselves, right?

Trotzdem würde ich zuerst beim Einfachsten beginnen, was Zündaussetzer hervorruft, nämlich den Zündkerzen! SinAre these new?

Ansonsten tatsächlich 3x Einspritzventil defekt, was entweder auf den Gasbetrieb zurück zu führen wäre oder irgendwo eine andere Ursache hat. (Spritzbild prüfen! DrecIs it in? (or Is it inside?)

Best regards from Munich!

"Hello, ignition coils along with their wiring and connectors would also be suitable, although visual inspections are really all that can be done. However, the coil is under greater stress when the engine is under load (compression), so it could weaken or fail."
If you really want to replace the fuel injectors (which I personally think is pointless), then please replace them all. VCDS cannot see whether or not each cylinder is firing, but it can probably monitor the smoothness of the engine running and the performance of each cylinder using various sensors.

Best regards,
Ronny

Good evening everyone.

Using logic, one could even argue that the question itself is irrelevant and therefore doesn't require an answer.

-The second question, which is quite imprecise, should relate to the first one.
Since the VSI control unit simulates an injection event for the engine control unit (ECU) during gas operation, there might be a fault in the signal processing within the VSI control unit.
However, I also want to point out that this may be due to improper installation of the gas system.
(Uninsulated solder joints on the electrical components of the gas system)

Since the misfires are now occurring during the injector replacement process, it cannot be due to either the wiring/connectors or the engine control unit (ECU)!

-One should never overlook the cause of an electric valve failure.
considering how compactly the fuel injectors are installed...
What effort is required to swap them around?
It would be disastrous not to check the lines immediately.
You've already seen horses vomiting .

In addition, a wiring diagram is not always available for every motor type.


Okay, let's assume that you didn't leave anything else 'along for the ride' besides the fuel injectors themselves, right?

-yes, that is correct.

What causes misfires is the spark plugs!

(my mistake)
- Of course, the spark plugs and ignition coil of the first cylinder were replaced.
Before I was involved in this case.
-Initially, at my instruction, the spools were swapped with each other to observe any potential changes, but this yielded no results.


Ansonsten tatsächlich 3x Einspritzventil defekt, was entweder auf den Gasbetrieb zurück zu führen wäre oder irgendwo eine andere Ursache hat. (Spritzbild prüfen! DrecIs it in? (or Is it inside?)

- What are these errors attributable to?
presumably increased thermal stress
This statement may be due to the measurement data related to the compression process.


Greetings from Berlin back to the Diesel Bear!





Hello Red R32.


'Hi, ignition transformers along with their wiring and connectors would also be a possibility...'
However, under load (compression), the transformer is subjected to greater stress, which could cause it to weaken or fail.

-No question, I'm thinking about thermal stress.

where only visual inspections can be performed.

I would like to object to that.
There is suitable measuring equipment available, but it can be quite expensive.


If you really want to replace the fuel injectors (which I think is pointless), then please replace them all.

'Since the injectors likely all have the same performance characteristics, replacing all of them would be a reasonable solution. However, this is ultimately the customer's decision. Let's not forget that each injector costs approximately €150.'





'Sorry for elaborating on the topic unnecessarily.'
Best regards,
Marco