Fuel Injector Problems? Get it Fixed!

I recently bought a Passat Variant V6 with automatic transmission (Tiptronic), manufactured in October 1999. However, I believe it's not performing as it should.

Problem 1: Fuel consumption at 150-160 is approximately 9.8 (city 12-13 L ). I read on a Forem forum that values as low as 8.3 L are also possible? So, it's actually not really drivable below 7.4 liters (highway at 60-90 km/h, driving calmly). Can anyone share experiences with the automatic transmission that show lower consumption? Max speed with long acceleration, according to the speedometer, is 208 km/h. The engine runs smoothly and achieves 0-100 km/h in 10.3 seconds!

I have the feeling that the car isn't pulling like it should for a V6 (high ).

The mass airflow sensor is new , but it's showing very low values (not reaching the target value).
Boost pressure control: OK (2121 millibar).

Since the timing belt wasn't replaced at the authorized service center, I have concerns.
The fuel injection pump is misaligned.
We logged something incorrectly with the VAG COM device.

Full load.
Engine speed specification. Start. Actual start. Cold start valve.
TIME 3800-4200 rpm 8-12 *BTDC 6-14 *BTDC
STAMP /min °ATDC °ATDC %
1.21 1949 4.0 4.8 63.9
2.41 2204 4.4 4.6 58.0
3.61 2459 5.0 5.0 51.7
4.81 2714 5.6 5.8 49.3
6.01 2970 6.4 6.6 46.6
7.21 3202 7.2 7.4 45.4
8.41 3434 7.8 8.2 43.0
9.61 3642 8.6 8.8 42.2
10.81 3828 9.4 9.4 38.3
12.01 4014 10.0 10.6 38.3
13.21 4176 10.0 10.2 38.7

Jogging.

Engine speed specification. Start. Actual start. Cold start valve.
TIME 3800-4200 rpm 8-12 *BTDC 6-14 *BTDC
STAMP /min · ATDC · ATDC %
0.81 742 1.0 1.0 74.6
2.01 742 1.0 1.2 77.3
3.21 742 1.0 0.6 78.9
4.41 742 1.0 1.2 76.1


Shouldn't the duty cycle sometimes increase to 95%?
Does this indicate a misadjusted fuel injection pump?

Engine speed / RPM
MAF sensor: Specified value
MAF sensor: Actual value
EGR valve duty cycle
TIME 740-840 180-270 mg/H 160-290 mg/H 40-75%
STAMP /min mg/R mg/R %
0.81 1856 867.4 537.7 95.5
2.01 2111 879.2 628.0 95.5
3.21 2366 879.2 714.4 95.5
4.41 2645 879.2 757.5 95.5
5.61 2900 879.2 777.2 95.5
6.81 3132 879.2 785.0 95.5
8.01 3364 879.2 777.2 95.5
9.21 3573 879.2 769.3 95.5
10.41 3782 879.2 741.8 95.5
11.61 3967 879.2 726.1 95.5
12.81 4130 879.2 702.6 95.5

Air volume decreases as speed increases, starting from a certain point.
Has anyone ever logged in and seen the number 879?

However, the mass flow meter should at least be able to reach the target value. Otherwise, something is wrong.
How new is the LLM?

Are you sure that the boost pressure was adjusted during the log recording?

I bought the mass airflow sensor from eBay, but it was still in its original packaging and unopened. I installed it about three weeks ago. Or do these things break down after being stored for a long time?

Here are the boost pressure readings.

Engine speed | Specified intake pressure | Actual intake pressure | N75 duty cycle
TIME | 2900-4000 | 1900-2300 mbar | 1900-2300 mbar |
STAMP /min mbar mbar %
0.41 1833 1958.4 1081.2 79.3
1.61 2042 1989.0 1897.2 43.0
2.81 2297 2009.4 1815.6 56.0
4.01 2552 2029.8 2040.0 50.5
5.21 2807 2040.0 2060.4 48.5
6.41 3039 2060.4 2101.2 47.3
7.61 3294 2091.0 2121.6 45.8
8.81 3503 2121.6 2142.0 44.6
10.01 3712 2121.6 2131.8 45.4
11.21 3898 2121.6 2131.8 45.0
12.41 4060 2111.4 2121.6 44.2

I would say they look good.

Hello Manuel,

Could you please share the part number of the mass airflow sensor you purchased? Just to make sure it's the correct one for your engine.

Slightly misadjusted valve timing (camshafts) is also a possibility, although the ESP seems to be okay because I can't see in the logs that the injection start timing is hitting its limit. However, I don't know enough about your engine for this, and only you can check it yourself.

Best regards, Rainer.

The old one was a 059-906-461-A, and the new one is a 059-906-461-E. As far as I know, the 'A' has been replaced by the 'E'. The engine is an AFB 2.5L with 150 horsepower. The buyer had the timing belt changed at a Hyndei dealer , which is why I'm also concerned that something might be misaligned. But to check this, you unfortunately have to disassemble the entire car. If the injection pump is set too early (e.g., the timing belt was incorrectly installed by one tooth), wouldn't a duty cycle of around 60% already be enough to adjust the injection timing to 10° BTDC? Or am I mistaken about that?

Hello Manuel,

I'm not very familiar with the V6 engine, but it would work with the AFN.
I once tried to start a car with a misaligned timing gear – it didn't work!

Hello Manuel!

The LMM is definitely the right one for the AFB engine.
'I'm also experiencing the same fuel consumption issue with an Audi A6 V6 TDI, which has the same engine. My father owns this car; it also has Tiptronic transmission and all-wheel drive. I drive the same model, but with a 6-speed manual transmission and without all-wheel drive.'
The fuel consumption of my father's car is in the same range as your Passat! Unfortunately, he can't quite verify whether the high fuel consumption has only been present since the timing belt was replaced (about 10,000 km ago), or if it was already that high 10,000 km before the replacement. I drove both cars on my usual route from Mainz to Frankfurt under as similar conditions as possible. In my car, the fuel consumption was 6.3 liters, while in my father's car, it was 9.5 liters.
I think the difference is too significant (despite the Tiptronic and all-wheel drive). I'll be checking the values with my laptop soon to see if anything unusual can be found.
Another thing about the LMM (Mass Air Flow sensor). I'm also seeing slightly lower than expected LMM values in mine, meaning it's not reaching its target value anymore. However, my LMM is already at least 2 years old, which might be the cause. It could also be that the EGR valve is leaking!
What I actually meant to say is that, in my opinion, the slightly low lambda (air-fuel ratio) value is not the cause of the fuel consumption, because despite those values and 193,000 km on the odometer, my car is relatively economical.

If you have any new information, I would be very grateful if you could post it here or send me an email!

Regards,
DENNIS

Hello Dennis,

Regarding the problem with the Audi, I can say the following. A friend of mine has the same Audi A6 Avant Allroad, and his fuel consumption is around 12.5-13 liters under fairly aggressive driving conditions. When I drive LONG distances on country roads, I get a consumption of about 7.3 liters (although I can't perform any full-throttle maneuvers), but for the first 15 kilometers, it's hardly possible to get below 10.5 liters.
It's noticeable that the coolant temperature displayed in VAG-COM doesn't go above 76°C and only reaches around 81°C after a fairly long drive. Meanwhile, the temperature gauge on the dashboard consistently displays 90°C.
I'll check the values on my colleague's equipment and see what readings it displays.

Bye, Manuel.

Hello Manuel,
I also drive a Passat Variant (AFB, TT5, 2WD, 12/99 with *** chip), and my MAF sensor values are similar (I can log the current values again if you want), but it consumes less fuel : 300km with an average speed of 169 -> 9.3 liters (afap ), on the same day, driving back in the rain, the average was 134 and 7.2 liters... calculated respectively.
Here are some other issues I'm having: There are marks on the camshaft lobes (and VW isn't responding), possibly a clogged catalytic converter (the cat has already been replaced), and a strange grinding/scratching noise when idling in gear D if the car is warm.

Regards,
Dieter.

PS: Does anyone need a used cat ?

Hello Dieter,

Is it possible for you to log the air mass values and boost pressure readings on your car?
I'd be interested to know if the air mass decreases as the engine speed increases in your case. Also, how do you notice the effects of the broken-in camshafts?

Best regards, Manuel.

Let's wrap up this topic.

Unfortunately, due to time constraints, I had my car serviced at the dealership (now I understand why they were so friendly to me ).

The injection timing and camshafts were misaligned as expected (likely only using markings during the replacement). An additional problem was that the camshafts replaced by VW were loose and not properly tightened during the replacement. Due to carelessness, valve adjustment shims that had fallen into the oil pan were simply left inside .

Conclusion: The engine now starts immediately on all cylinders. Fuel consumption for a 300 km highway trip, driving between 150-170 km/h and then 200 km/h, was 8.7 liters.
I couldn't test the top speed because of the winter tires. I drove on a country road from Straubing to Neukirchen and back (50 km), using normal driving habits, and consumed 6.7 liters of fuel.

The only weakness of the engine with automatic transmission: fuel consumption in the city with a cold engine (below 5°C, distance 10 km) -> on a hilly route, fuel consumption is approximately 12.5 liters.

VW now specifies that the crankcase pressure should not exceed 25 mbar. Otherwise, wear on the seals of the oil pan components will be very high, and replacement will be more or less complex.

Best regards, Manuel.

Quote:

The injection timing and camshafts were misaligned as expected. (Probably only markings were used during the replacement). An additional problem was that the camshafts, which had been replaced by VW, were loose and not properly tightened during the replacement. Due to carelessness, valve adjustment shims that fell into the oil pan were simply left inside.

Hi, thanks for the feedback!