Is My Timing OK?

As our TDIs age, many people are discovering the value of VAG-COM Diagnostics from Ross-Tech. With a VAG-COM Cable and a laptop you can clear fault codes, diagnose issues, and fine tune your TDI engine. This is the first in a series of articles we’ll provide to help you improve your repertoire of VAG-COM skills.

One of the most basic VAG-COM uses is checking timing after a timing belt change. We’ll walk through that process here. In addition, adjusting your timing to be slightly (or more) advanced can improve cold starting, accelerator response, and fuel economy. So there are a lot of good reasons to have your timing set properly.

Here’s how to check.

Cable/Software/Port Setup

This how-to assumes that you’ve got your VAG-COM, downloaded the software, and made sure your car can connect to your computer. If you haven’t done this yet, www.ross-tech.com has detailed instructions.

Checking Timing

You car has to be running to check the timing. And it has to be up to operating temperature. VAG-COM also measures fuel temperature, and will provide slightly different readings if the fuel is cold. So it’s best to drive the car for 20 minutes or so, some of it at highway speeds, to make sure you’ll get a good reading.

The screen prints in this article are from a 1997 VW Jetta TDI. If you have a different TDI some of the data displayed may be slightly different, so keep that in mind as you proceed.

You’ll first see this screen:

This is where VAG-COM launches. Click on the button named Select under the the words “Select Control Module.” Next you’ll see this screen:

All the engine control modules are listed, even if your car doesn’t have some of them, such as ABS. Click on 01-Engine to proceed and you’ll see something like the following screen:

The engine data will take a moment to populate. Newer cars populate faster than older ones (slower ECUs). Once the screen is populated, you can click on Basic Settings-04 to see the timing data, shown below:

When this screen appears you won’t see the blocks with timing data as shown above. Hit the Enter key on your laptop for this data to display, or click the Up button under the Group label to Group one, and then click back Down to Group 000 to display the timing.

The data you’re after is in Block 2. In the sample screen it shows a timing setting of 64. Although the measurements vary by vehicle, this timing is advanced but within spec for most TDIs. If you want to see a graph click on the TDI-Timing button on the lower right of the screen and you’ll see the following:

This screen shows several pieces of data.

• The Red, Blue, and Green lines show the limits of timing within spec, from most retarded (red), to normal (blue) to advanced (green). The yellow line shows how the timing is set on your car. In this example it’s advanced, but within specifications.
• You’ll see fuel temp in the lower left of the screen. It shows 95F here. If the fuel is too cold you’ll see a warning message at the bottom of the graph.
• Also at the bottom of the graph you’ll see Result. In this case it says Timing within spec slightly advanced.
• However, on the right side of the graph you’ll see a drop down box where you can select the engine that most closely matches your car. And in this case you can see a 1.7l R4 SDI selected, not the 1Z/AHU that an A3 Jetta has. So the graph is calibrated for an engine different than the one in the sample car. You should choose a graph that most closely matches your engine (which we failed to do here) to get the most accurate data on your car’s timing

What do I do with the data?

As previously mentioned, timing settings can affect starting, power, and fuel economy. And timing that is way off can potentially damage your engine.

If you don’t see any data on the graph, or if your timing number is over 150, your timing may not have been set properly when your car was serviced. Your timing belt may be off at tooth, or even two.

The ECU will do its best to correct timing issues when the engine is running over 1600 RPM. Since the timing measurement is taken at idle, you won’t see any ECU correction in the screens above. And the ECU cannot compensate for retarded timing in during a cold start.

Correcting Timing

In rotary pump cars, timing should be set mechanically, not in VAG-COM. Tuners will fine-tune timing in VAG-COM, but it’s generally accepted that the best way to set timing is by changing pump position (1Z and AHU) and the pump cam (ALH). Timing can be fine-tuned in VAG-COM in Pumpe Deuse TDIs, which will be the subject of a future article.