Changing Injection Quantity (IQ) is easy. Here’s how to do it.

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 and Changing IQ

You car has to be running to get an accurate injection quantity reading. And it has to be up to operating temperature. 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. You should not run your A/C during this test, as it will affect readings.

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 Login-11 to first login:

Type the numbers 12233 into the box to the right of the words Enter Code and click on Do It! This will take you back to the Engine screen:

This time click on the button Adaptation – 10. Next the screen below will appear:

However, you’ll see channel 00. Click the Up button to Channel 01 and you’ll see Adaptation numbers.

At the top of the screen you’ll see RPM and Injection Quantity. The IQ will most likely be a number between 1.0 and 3.0.

Next, look at the numbers on the left side of the screen. Below the Channel window you’ll see two boxes, one titled Stored Value and the other titled New Value. The default stored value is 32768. If your IQ has been previously adjusted you may see a different number. There’s a limit on the number range for IQ, it varies by ECU, but is approximately between 32645 and 32786.

The IQ measurement numbers are slightly counter-intuitive. A higher Injection Quantity (such as 3.0), will flow less fuel than a lower quantity (such as 2.0). And a lower new value (such as 32725 instead of the default 32768) will flow less fuel than a higher new value.

Why change Injection Quantity?

If your car:

• Smokes more than you want
• Shudders at slow down or idle

You may want to reduce fueling (increase the IQ number)

If your car is low on power, you may want to increase the IQ number.

Changing IQ

Here’s how to do it. On the adaptation screen, shown below:

Click into the New Value box and type in a new number. If the stored value is 32768 and you want to reduce fueling, try a lower number such as 32750 or 32725. Click on Test at the bottom of the screen. The IQ number will change (and your engine tone will change, too). Look at the new Injection Quantity at the top of the screen and see if it’s what you want. You can further adjust the IQ by typing in a new number and clicking on Test, or by using the up and down buttons to the right of the New Value box.

Once you’re satisfied with the IQ and want to test drive the car to gauge results, click on Save at the bottom of the screen:

You’ll be asked, Are You SURE?

Click on Yes to save the new setting. If you want, you can drive the car with the computer hooked up to determine if you’ve achieved the result you were after (more power, less shudder), and further adjust the IQ if needed.

Once you’re satisfied, click on Done, Go Back at the bottom of the screen, Back on the engine screen, and Exit on the main screen to exit VAG-COM.

Done!

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.