ECU Tuning: Definition & Connector Use

Hi!
I haven't really enjoyed my Golf3 GTI TDI (AFN) for about 3 years now.
Since I bought it with 65,000 km on the odometer, the torque has been poor.
The seller said he had only driven the car for 9 months, covering only 10km per day. However, because the overall condition was extremely good, I ended up buying it. After driving it at full speed on the highway for a while, it was reasonably okay. I have to mention that I previously owned a Golf2 GTD with only 70 horsepower, which isn't exactly known for its power, so it's hard to compare.
About two years ago, I decided to have a HOPA tuning module installed. When I picked up the car from the tuner (who was passing through), the performance was excellent. There was a huge boost in power right from idle. However, this only lasted for about 9 weeks. Then, the power disappeared. Since then, I haven't really worried about it, and I also didn't have a receipt for the HOPA.
So, I removed the module, and lo and behold, the performance was even worse.
Four weeks ago, I took the car to a workshop that has a good diagnostic system (Würth). They found that the fuel injection pump was not properly adjusted, and the mass airflow sensor was reading too high (by 1500). The target value is 2500, but the actual reading is 4000-4200. The engine control unit is operating based on this data.
After that, I naturally obtained and installed a new mass airflow sensor. However, even after that, the performance didn't return. The deviation is the same as it was with the old one.
Today, I adjusted (rotated) the fuel injection pump, and also...
It didn't fix anything. Then, the mechanic called someone who said that it sometimes happens that the tuning modules in the pump's wiring harness increase the voltage to the engine control unit to such an extent that the control units can be damaged.
Since replacing a part based on suspicion can be quite expensive, I wanted to get the opinion of experts on what the best course of action is.

As I mentioned, the tuning module is from the company Hopa and has a connection to the mass airflow sensor. (The connection was also disconnected in order to test the mass airflow sensor. The reading remained the same whether it was connected or disconnected.)

Thank you!

Hello,

moser7 wrote:

... which have a good diagnostic system (Würth), we found that the fuel injection pump is not properly adjusted, and the mass airflow sensor is reading 1500 too high. (Target value 2500, actual value 4000-4200

It's less about the quality of the diagnostic system itself than it is about the people who use it .
Unfortunately, I can't make any sense of the target values you provided. What unit of measurement are you using? Are we talking about 2500 apples or pears?
The air mass is measured in mg/stroke and rarely exceeds 1100 mg/stroke, especially not at an engine speed of 1500 rpm.
Furthermore, I have never experienced a loss of performance due to excessively high

Quote:

air mass readings, so the purchase of the mass airflow sensor was probably a waste of money. Which setting on the injection pump was incorrect? In the technical article on adjusting the TDI 1.9L distributor injection pump, you will find a diagram that should allow a mechanic, using a diagnostic system, to check the injection timing. What values are displayed under the boundary conditions mentioned in the article? The article also describes a test that can be performed using a multimeter, which you can use if you don't have access to a diagnostic system.

Subsequently, the mechanic called someone who said that it sometimes happens that the tuning modules in the pump's wiring harness increase the voltages to the engine control unit to such an extent that the control units can be damaged.
I'd say that's another waste of money.
All the turbochargers that I know of either increase boost pressure or fuel injection by having the measured values sent to the engine control unit reduced by a factor}, so that the engine control unit adjusts in the direction of 'more'.

First, disconnect the box.

For finding a solution to your problem, the following information is relevant:
- Have the engine control unit's fault memory read immediately; any VW workshop will do this for a small donation to their coffee fund and it takes 2 minutes. Be careful that nothing is deleted (some mechanics might do this intentionally to make troubleshooting more difficult, and I've encountered two like that). It's best to have the fault memory printed out.
- Does your vehicle emit black smoke when running at full throttle, and if so, at what engine speeds does this occur most frequently?
- unusual engine noises, such as noticeably louder knocking when accelerating at full throttle in the higher RPM range.
- Is the engine noticeably quiet in the higher RPM range?
- When accelerating, are there noticeable air bubbles or even foam visible in the transparent fuel line connecting the diesel filter to the injection pump?
- Does your car run better with the MAF sensor connector unplugged? How does the performance compare to when it's plugged in?
- Even with the low torque, can you reach the top speed? What does the speedometer show?

Best regards, Rainer.

Hello again!

Okay, I'm trying to gather everything together again here:

I'm not entirely sure which unit we're talking about. I only know that the amount of air the engine control unit is working with is too high.
And if more air is indicated than is actually present, won't less fuel be injected as a result? Thus, wouldn't that also reduce power output?

Regarding the questions:

The vehicle doesn't produce any smoke without the tuning module! (At least, it's not visible in the rearview mirror.)

The engine sound seems to be different from other 4-cylinder TDI engines with a distributor injection pump, because recently a friend of mine said that my engine sound is completely different from his 90hp Audi 80.
It sounds much grumpier and deeper. Furthermore, inside the car, between 1200-2400 RPM, you can hear a scraping noise, which, according to the VW workshop, is supposedly the turbocharger. However, according to the measurements, the boost pressure is either okay or even too high. Especially when the engine is warm, you can hear a rattling noise when giving it a little gas.
As soon as you let off the gas, it disappears. Other TDIs I've ridden in don't do that. They always sound rough and powerful.
Or is the insulation in the Golf 3 that bad?

For a while, when accelerating, it was possible to detect a noticeable drop in power or a jerky feeling within a fairly precise range of 2200 to 2400 RPM.
It's not there anymore.

The car performs worse with the tuning plug disconnected (as described), but with the plug disconnected, the idle is more stable.

The maximum speed is easily reached. The speedometer reads between 210-220 km/h when accelerating fully with the air conditioning on. Then, the engine actually becomes quieter again.
The speed may occasionally creep slightly into the red zone.

Perhaps it can be said that everything is fine in the higher RPM range, but the 'oomph' is missing in the lower range.

Possibly some residual VTG?

I received an error message today (while tuning): fuel control valve.

Otherwise, the message 'quantity adjuster at lower limit' would often appear (even with the tuning). This error message hadn't appeared for about 6 months.

The fuel injection pump was calibrated such that, for example, at a fuel temperature of 150, it initiated fuel injection at a timing of 18.
Okay, so approximately 42. However, this has not changed anything regarding its running characteristics or performance.

It should be noted that the engine runs very roughly, and the entire car vibrates at idle, even though the engine mounts were replaced only 3 months ago. (I haven't observed this on other TDI engines before. We have many Golfs and Passats, some of them quite old, but they don't vibrate like this.)

Thank you for your patience, but if things don't improve, I'll probably end up buying a gasoline-powered car, and I don't think any of us want that, do we?

Basically, you can definitely damage the engine control unit (ECU).

However, it's a bit more challenging in the automotive sector.
It is certainly possible that a museum entrance was shot at, but I think it is rather unlikely.

I would start by checking the VTG (variable turbine geometry) and cleaning the AGR (selective catalytic reduction) system.
If that doesn't work, have the fuel injectors checked. If the previous owner really only drove 10km to work and back, and hardly anything else, it's quite possible that the components are gummed up.

The fuel injection quantity message is clear... it indicates a huge fuel injection volume ('thanks' to the box) and an attempt to maintain the idle speed...

The LMM values, as Rainer says, are unusable. Unless you use euros as the unit and transfer the amount to me .

CU Gremlin.

Hello.

moser7 wrote:

I only know that the amount of air that the engine control unit is working with is too high. And if more air is indicated than is actually present, then less fuel is injected, or? Thus, also less power!?

How do you know that? Are those the 2500 pears?
If the mass airflow sensor provides excessively high readings, the engine power will not be reduced unless a defect in the mass airflow sensor is detected.

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The vehicle does not produce smoke without the tuning module! (at least not visible in the rearview mirror). Furthermore, inside the cabin, between 1200-2400 rpm, there is a scraping noise, which, according to the VW workshop, is supposed to be the turbocharger. However, according to the measurement, the boost pressure is okay or even higher. Especially with a warm engine, a rattling noise can be heard when applying light acceleration. As soon as you take your foot off the gas, it's gone.

"This indicates a leak in the intercooler system, but it directly contradicts your statement that your car is not visibly producing smoke."
Please perform the Ulf test and provide the results.
Furthermore, the boost pressure values in the low torque range are interesting. Drive in 3rd, or better yet 4th gear, give it full throttle, and have a passenger record the values approximately every 0.5 seconds. Ideally, the boost pressure regulation process should be recorded using a diagnostic tool.

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The car performs worse with the tuning plug disconnected! (as also described), however, with the plug disconnected, the idle is more stable.

Logically, you should also leave the box turned off for all measurements, and only temporarily disconnect the air mass sensor plug for testing purposes...
Was the measurement of the top speed taken with or without a speed trap?
The quality of a remote diagnosis depends on an accurate description of the problem.

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The maximum speed is easily reached. The speedometer reads between 210-220 when fully accelerating with the air conditioning on.

Can it be said that the torque, when accelerating, only reaches its full value briefly at around 2000 rpm, then drops, and only recovers and increases again at engine speeds above 3000 rpm?

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Today, I received an error message (while tuning): fuel control valve

.
Please provide the complete error message text/code.

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Otherwise, the message "quantity adjuster at lower limit" appeared more frequently (even with tuning).

This error message had not appeared for about 6 months.
Is the idle speed setting on the box too high? If the problem doesn't reappear, leave the setting as it is.

Furthermore, please review my questions again. What about the fuel line to the injection pump? What is the top speed according to the speedometer (so you don't accidentally use the wrong channel for the climate control)?

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Since purchasing the car with 65,000 km, the torque has been poor

.
I'm actually less interested in how many kilometers you had on it when you bought it, but rather how many kilometers you have now :wink:on it}.

Best regards, Rainer.

Rainer K. wrote:

Unfortunately, I can't do anything with your target values; what unit are they supposed to be in? 2500 apples or pears?

Hello Rainer,

I am very familiar with the Würth system and have always used it until I got a VAG Com. The system only displays values, but these values do not have units, making them not comparable to VAG values.
"There's been a new version available for a few days now, and my painter asked me to check the system again. I can take a look and see if anything has changed."

Sorry, but I'm just not a professional! That's why I'm turning to this forum.

So, the Würth system was plugged into the diagnostic interface today, next to the ashtray.
The values for the NEW mass airflow sensor were identical to those of the supposedly defective one, both with and without the tuning plug.
According to Würth, the target value should be 2500, but the actual value was 4000. Now, you can calculate the percentage by which the actual value exceeds the target value.
Namely, by approximately 60%! You can then add this information to your respective units.
We had approximately 22 degrees Celsius today, with high humidity.

The vehicle has a mileage of 160,000 km.

I would like to reiterate that the engine performs well in the higher RPM range, starting around 3000 RPM. In the lower RPM range, however, there isn't much happening.
(Normally it's the other way around, or is it?).

The problem with diagnostic procedures is as follows:
The VW workshops nearby have no interest in seriously helping me. Two weeks ago, I wanted to do a series of tests with a master mechanic, and he said that would cost 60 EUR!!!!!!!
And my current workshop is about 50km away and is very busy.
Besides, I've learned that it's best to clearly explain to the workshops exactly what's broken, otherwise, you can easily end up paying a month's salary. (But that's just a side note.)

The Vmax measurement was done with the aerodynamic kit (box). Without the kit, a top speed approximately 8-10 km/h lower is achieved, and it takes longer to reach that speed. By 'climate,' I meant that the Vmax measurements were taken with the air conditioning turned on, in warm temperatures. In my car, I notice a significant difference between having the air conditioning on (regular mode) and having it off (ECO mode).
The data was read from the speedometer.

No, the torque is moderately better above the idle speed, specifically above 3000 RPM (or the power delivery improves).

I still need to check the fuel line leading to the injection pump, but it's dark now!

Furthermore, it can be said that the performance is better when the engine is cold compared to when it is warm. Around an outside temperature of approximately 26°C, there is hardly any power left. The engine seems to be struggling at that point.

However, occasionally, there may be a significant amount of power available for acceleration.
However, this issue should be resolved as soon as the ignition is turned off and the engine is restarted. But this only occurs in a maximum of 5% of normal driving conditions.

'The vehicle's fuel consumption cannot be kept below 6.5 liters, regardless of whether you're driving at full throttle on the highway. For a short period, the tuning module produced the promised power, or the engine itself did, and during that time, the fuel consumption was 8 liters. Therefore, it seems that too little diesel is being injected. I am definitely not a slow driver, and an average fuel consumption of 6 liters, often with full throttle, is already very good, isn't it?'
(With summer weather!)

Phew, I thank you for your patience. I really don't know what to do anymore, and I can't afford any more expensive visits to the workshop where they replace parts based on suspicion. THANK YOU!

Hi,

moser7 wrote:

The values for the NEW mass airflow sensor were identical to those of the supposedly defective one. This was true both with and without the tuning plug. According to Würth, the target value should be 2500, but the actual value was 4000. Now, you can calculate the percentage by which the actual value exceeds the target value. Namely, by about 60%!

The question is, at what speed and engine load was this measurement taken? As you describe it, the measurement has no meaningful value.
If the issue was related to the idle speed, the mass airflow sensor (MAF) value could still be okay if the exhaust gas recirculation (EGR) system was disabled during the measurement.

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The vehicle has a mileage of 160,000 km.

So, not yet completely used up .

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I still need to check the

hose leading to the fuel injection pump, but it's dark now!

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If the maximum speed is easily reached without the airbox, it's very unlikely that leaks or blockages in the fuel lines will improve as the engine power increases. It wouldn't hurt to check, but I don't believe the cause lies there anymore. Any leaks present should still be fixed.

No, the torque is moderately better above 3000 RPM (or the acceleration improves). However, occasionally, there can be a huge amount of power available for an acceleration.
This, however, will be resolved no later than after turning off the ignition and restarting it.
Okay, that's a useful statement!
I suspect that your VTG (Variable Turbine Geometry) adjustment on the turbocharger is not being set to the "maximum boost pressure" position. This could be due to several reasons:
- Vacuum hoses for the turbocharger pressure adjustment are leaking or loose. Check all} hoses in the vacuum system for proper seating and cracks, and for signs of rodent damage! The best way is to remove each hose (carefully noting or marking where it was previously connected!), hold one end with your finger, and suck strongly on the other end. Another indication of leaking vacuum hoses would be increased air mass readings at idle, as the exhaust gas recirculation (EGR) system cannot be activated without sufficient vacuum. If your vacuum hose from the exhaust gas recirculation (EGR) valve has "come off," make sure the hose is securely closed with a screw or similar, or reattach it to the valve.
- The membrane in the vacuum-operated valve on the EGR system or the adjustment valve on the turbocharger may be defective. A quick test can be performed by sucking on the valve (if air is escaping, the valve is definitely faulty). If the valve appears sealed when sucked on, use a large syringe or a modified bicycle pump (turn the rubber plunger inside out) to actuate the valves (the one on the EGR system and the adjustment valve on the turbocharger) and check if they are sealed.
- Wastegate solenoid valve defective due to mechanical failure.
- The adjustment on the turbocharger is stuck.

Please read the technical article on variable turbine geometry (VTG), as it contains further tips for testing and troubleshooting.
"Please do not change the length of the VTG adjustment rods! Since your car ran normally for a while, the length must be correct. However, please check that the lock nut on the VTG adjustment rod, which connects to the vacuum actuator, is securely tightened."

Best regards, Rainer.

Hi!

Aha, ich werd das mal prüfen! Thank you.
If you come up with anything else, please let me know.

Sincerely,
Benjamin.

First, I would check the vacuum hose connecting the vacuum pump on the engine to the Y-connector, which then leads to the two solenoid valves on the injection manifold. I would also check the Y-connector itself.

Okay, so...

I've reviewed the entire matter again.

I have both hoses for the pressure sensors (one at the turbo and one for the AGR).
The AGR hose is leak-free, and there's no whistling sound coming from the valve either.
I also vigorously sucked on the hose for the adjustment, and the adjustment can be easily operated with back pressure. It does squeak a bit, but it works. All the other hoses are okay.

Is the boost control valve the one located on the inner side of the fender, next to the air filter housing? Or is it the one further back, next to the diesel filter?
I haven't checked them yet. All I can say is that with the engine off, there's a clear passage through the valve behind the air filter, connecting the air filter box to the turbo pressure sensor.

Okay, I can't really do much more. How much does the solenoid valve cost?
Are the two components identical (AGR and Turboventil)? The part numbers are identical except for a single letter.

Sincerely,
Benjamin.

Hello,

moser7 wrote:

I also vigorously sucked on the hose for the adjustment, and the adjustment can be easily operated with back pressure. It squeaks a bit, but it works. All the other hoses are okay.

Okay, stand next to the car and carefully observe the VTG adjustment mechanism while an assistant starts the engine and lets it idle.
It's best to do this with a cold engine, as you should manually check whether the VTG lever is fully engaged in the "maximum boost pressure" position when the engine is started, or if it remains slightly before that position.
"Furthermore, the adjustment range of the lever is of interest. Please specify the differences in millimeters when the engine is off and at idle."

Quote:

Is the boost control valve the one located on the passenger side, inside the fender, behind the air filter box? Or is it the one further back, next to the diesel filter? I haven't checked those yet. All I can say is that with the engine turned off, there is a clear passage through the valve behind the air filter in the line from the air filter box to the turbo pressure control valve.

I'm not familiar with the engine compartment of the Golf 3.

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Okay, I can't really do much more. How much does the solenoid valve cost?

It varies; prices have been mentioned in this forum before, and I haven't had to replace mine yet.

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Are the two parts identical (AGR and turbo valve?) The numbers are identical except for a single letter.

It's kind of both. They are not the same, but for a test, you can try swapping them.

Unfortunately, you haven't yet answered my question about the LMM values. Was the measurement taken at idle or under the specified operating conditions?

Best regards, Rainer.

Okay, I've got it now.
The boost pressure control valve was responding too slowly.
It took approximately 8-9 seconds for the turbocharger to reach full boost pressure.
With the new version, it's much more effective again.
Der Monteur hat mir die AGR stillgelegt, er meint, das bringt sowieso nix, und so ist es besser. Was meint Ihr?
Desweiteren würde mich interessieren, wenn man in die Ladedruckleitung die zum Steuergerät führt einen Druckminderer einbaut, um so ev. noch
0,1-0,2 Bar mehr zu bekommen (Turbo liefert 1,6Bar wenn er losgelassen wird). Geht das?

Hallo,

moser7 wrote:

So, nun hab ichs. Das Ladedruckregelventil hat viel zu träge geregelt. Bis voller Ladedruck anlag, vergingen so ca. 8-9 Sekunden. Mit neuem ist er wieder viel bissiger.

na das ist doch ein Erfolg !

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Der Monteur hat mir die AGR stillgelegt, er meint, das bringt sowieso nix, und so ist es besser. Was meint Ihr?

Siehe Suchfunktion

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Desweiteren würde mich interessieren, wenn man in die Ladedruckleitung die zum Steuergerät führt einen Druckminderer einbaut, um so ev. noch 0,1-0,2 Bar mehr zu bekommen (Turbo liefert 1,6Bar wenn er losgelassen wird). Geht das?

Er liefert eben keine 1,6bar ohne die Gefahr SOFORT hopps zu gehen. Theoretisch gehts mit Druckminderer, praktisch gibt es bessere Methoden. Ebenfalls Suchfunktion und Artikel zum 10C Tuning.

Grüße, Rainer

moser7 wrote:

Das Ladedruckregelventil hat viel zu träge geregelt. Bis voller Ladedruck anlag, vergingen so ca. 8-9 Sekunden. Mit neuem ist er wieder viel bissiger.

Hi

das heißt also, die Fahrleistungen siond wieder normal?

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Der Monteur hat mir die AGR stillgelegt, er meint, das bringt sowieso nix, und so ist es besser. Was meint Ihr?

Technisch hat er wohl recht, aber die Geschichte ist illegal --> AGR-Fachertikel lesen.

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Desweiteren würde mich interessieren, wenn man in die Ladedruckleitung die zum Steuergerät führt einen Druckminderer einbaut, um so ev. noch 0,1-0,2 Bar mehr zu bekommen (Turbo liefert 1,6Bar wenn er losgelassen wird). Geht das?

Geht ja, aber ob es sinnvoll ist (Lader-Lebensdauer)?

Außerdem gibts zur Ladedruckerhöhung eine "unauffälligere" und in Eigenregie praktisch kostenlose Methode, siehe Fachartikel über 10c-Tuning.

Das mit dem 10Cent Tuning hat sich wohl erledigt, da ich bereits
ein Hopamodul habe.
Die Fahrleistungen sind jetzt wieder o.k.

Durch die stillgelegte AGR ist der Motorlauf nach Start viel besser geworden.

Jetzt russt der auch nicht mehr so stark, da er wieder mehr Luft bekommt.