VAG-COM: Check NW/KW Timing on PD Engine

Hello,

"After I replaced the timing belt myself, the fuel consumption has increased dramatically (20% in 7,000 km). The engine is a 1.9 TDI 74kW PD in a Golf IV Variant, manufactured in October 2002, with 97,000 km on the odometer. It runs on biodiesel and has winter tires."

1) Can a misalignment between the camshaft and crankshaft be introduced by subsequently tightening the timing belt (e.g., due to belt elongation), which could cause this increase in fuel consumption?

2) I don't have time today to check the NW (negative crankshaft variation) and KW (positive crankshaft variation) on the right side, but I could run VAG-COM during the next 500 km of highway driving. Based on which readings can one infer the NW-KW offset, if that's possible?

Later, I'll also fill up with mineral oil diesel and observe the fuel consumption (I haven't done that in months). Oh yeah, it also starts poorly, but that might be due to the biodiesel.

Best regards, Christian.

"I experienced the same issue with a Passat equipped with a 74kW PD engine. Originally, the camshaft was set a few degrees behind the crankshaft. I then adjusted it so that both timing marks aligned (camshaft timing pin, crankshaft precisely on the mark)."

It also had slightly higher fuel consumption, but it performed better at higher RPMs.

I left it as it is.

If you still remember the settings from before the change, set them back the way they were.

In my case, the camshaft was lagging by approximately 3 degrees of crankshaft angle.

Chr_Meissner wrote:

Based on which measurements can one infer the northwest-southeast shift, if possible?

Hi,

The only value that might potentially provide something like that is the synchronization angle (MWB 4, far right), which should be approximately -3... +3° depending on the MKB.

But in none of the explanations I am familiar with does it explicitly mention a wrong network configuration as a possible cause for exceeding the tolerance , rather it mentions things like...
Hall sensor - G40 - defective.
Wiring interruption/short circuit to ground (Hall sensor -G40- loose).
Damaged/twisted donor wheel.
Clearance between the distributor and the camshaft gear is not within specification.

Hello,

I will log this set of measurements once.

I had already noticed that the camshaft and crankshaft were not perfectly synchronized in the old timing belt, but I thought it might be due to the belt stretching after 90,000 km (which would cause camshaft lag).

Thank you for your replies. I'm going to try to get onto the highway now.

Best regards, Christian.

Chr_Meissner wrote:

... Later, I'll also fill up with mineral oil diesel and observe the fuel consumption (I haven't done that in months). Oh yeah, it also starts poorly, but that might be due to the biodiesel.

A few weeks ago, I accidentally put biodiesel (BD) into my car's gasoline tank (it was a mistake by the gas station) -> Starting: very difficult -> Performance: very poor -> Increased fuel consumption by 20-30%.

The AXR might not like BD at all when it gets colder. Below 5°C, it jerks and sputters with BD as if it's resisting the stuff.

By the way, it is correct that the OT1 marking does not align with the staked position of the NW. This must be the case. Only the staking tool on the KW indicates the correct position of the KW relative to the NW.

EDIT: Attached is a picture of a correctly adjusted AXR. On the transmission side, the timing window was also significantly off (approximately 2-3° KW).

Thank you very much.

With an average speed of 112 km/h, and driving 90% on the highway, I achieved a fuel consumption of 7.2 liters per 100 kilometers over a distance of 450 kilometers. In the summer, I had the same fuel consumption at an average speed of 135 km/h (in both cases using biodiesel).

"However, there are some things I don't understand."
- Coolant: 90°C
- Fuel, after preheating: 50°C.
- Intake temperature: approximately 40°C (after the turbocharger).

Where should the winter influence be reflected?

Regarding the timing (MWB 04, far right): 1.1° with a cold engine, 0.0° with a warm engine. During the timing belt replacement, a crankshaft stop was also used, meaning the position was actually correct.

The measurement of the same route using a Mineral Diesel engine will take place in early January.

Best regards, Christian.

Hello,

"Really! It actually drives better in the winter without biodiesel. On the return trip (450 km) at a slightly higher speed, the engine consumed "only" 6.8 liters instead of 7.2 liters per 100 km. Above all, the engine starts much better."

I'll still take a look at the timing belt, though.

Thank you for your responses.
Best regards, Christian.

@Bertil:

Take a look at the hole in the pulley where the crankshaft sprocket engages; there's quite a bit of play there. The marking on the belt drive side is only meant as a rough guide, probably to help a mechanic prevent the engine from rotating past top dead center.

Haegar wrote:

@Bertil: Take a look at the hole in the pulley

, where the pin on the crankshaft sprocket engages; there's quite a bit of play there. The marking on the belt drive side is only intended as a rough guide , probably to prevent the engine from rotating past top dead center by a mechanic.

Those who can read have a clear advantage.

"Quote from above..."
On the transmission side, the OT window was also significantly off (~2-3° KW)}.

This offset is not the same for all MKBs.

hello,

'Did you use the crankshaft alignment tool and the camshaft dowel pin? If you didn't, you shouldn't be surprised by your fuel consumption. As I said, the markings on the pulley and flywheel are just approximate values. It's essential to use the specified alignment tools when replacing the timing belt on pump-injector engines.'
Furthermore, have you checked the rubber damper on the camshaft pulley? These parts become soft over time and are responsible for the valve timing being incorrect above an engine speed of 3000 RPM, which can also cause issues with your fuel injection maps.

Best regards.

tdi pumpe düse wrote:

hello, "Hey, did you use the crankshaft alignment tool and the camshaft alignment pin?" ....

Hey, did you all forget how to read?

Quote:

... During the timing belt replacement, a crankshaft stop was also used...

Oops, sorry, I must have missed that. It happens sometimes.
I've seen some professionals use a permanent marker to mark the timing, and they later wondered why their car didn't run as well as it did before. The same applies to people who rely on the markings on the pulley and flywheel. Sorry again.

Best regards.

ups, sorry, I missed that, it can happen sometimes.
I've seen some professionals use a permanent marker for this method, and they later wondered why their car didn't run as well as it did before. The same applies to people who rely on the markings on the pulley and flywheel. Sorry again.

best regards

Hello 'tdi pump nozzle',

Your comment startled me.
I drive an AJM engine that will soon need its second timing belt replacement at 120,000 kilometers.

Where is the 'tensioner' located, and is it usually replaced during a timing belt change?

Sure, here is the translation of the text from German to English:

'Hello'
herwig

Okay, to answer your question, the timing sprocket is NOT replaced during a timing belt change. It's located behind the timing belt pulley, and that part is also called the hub, which is bolted to the crankshaft. The camshaft sprocket then sits on top of that hub. Believe me, this part is prone to failure because the rubber in the timing belt can become soft and, in the worst case, even disintegrate. I know this because I've been working with these engines since their development, and I'm very familiar with them. I can't tell you much more here. Replace the part; it costs around 40 euros.

Sure, here is the translation of the text from German to English:

'Hello'

So, to answer your question, the timing sprocket is NOT replaced during a timing belt change, and it's located behind the timing belt pulley. This part is also called the hub, and it's bolted to the crankshaft. The camshaft sprocket then sits on top of it. Believe me, this blasted part is prone to failure because the rubber timing belt material becomes soft and, in the worst case, can even disintegrate. You can believe me because I've been working with these engines since their development, and I know them very well. I can't tell you much more here. Replace the part; it costs around 40 euros.

greeting

'Thanks! - I will.'

tdi pumpe düse wrote:

So, to answer your question, the timing sprocket is NOT replaced during a timing belt change, and it's located behind the timing belt pulley. This part is also called the hub, and it's bolted to the crankshaft. The camshaft sprocket then sits on top of it. Believe me, this blasted part is prone to failure because the rubber timing belt material becomes soft and, in the worst case, can even disintegrate. You can believe me because I've been working with these engines since their development, and I know them very well. I can't tell you much more here. Replace the part; it costs around 40 euros. greetings

*excavating the body* One wonders why one of the specialists who has been present here for some time didn't mention this a long time ago!?
Those few euros won't make much of a difference!