Magnet Valve Failure: Vacuum & Pressure Issues

Hello again.

To the 12 people who have already read this post in its original version: I have been able to significantly shorten it, now that some of the problems have been resolved (when assembling, one should think about all the connectors )...

However, let's now turn to the current problem:

My Audi 80 1.9 TDI 1Z automatic, manufactured in November 1994 (used car with 129,000 km and a previous engine failure), suddenly loses power when accelerating in the highest gear. Initially, this happens around 120 km/h. If you release the accelerator and then press it again, it continues until approximately 140 km/h, and it's not possible to go above 160 km/h on a flat road.

When I picked up the car from the workshop (before my 'self-experiment'), I was given a fault report containing the following entry:

'00575 017 Intake manifold pressure, control difference, intermittent fault.'

'That doesn't mean anything, that's irrelevant, the car is fine now!'?!

Can the aforementioned error message be related to the performance issues?

Based on the numerous posts describing this issue, it's likely that the problem lies with the magnetic valve for turbocharger boost control. So, with the help of Dieter Korp ('Now I help myself,' Volume 163, Audi 80 TDI), I took a look at that part.

1) I have checked the power supply of the plug; it is working correctly. The battery voltage is present at contact 2.

'According to Dieter (Korp), the internal resistance should be between 24 and 28 ohms. I measured 29.9 - 30.0 - could this already be the cause of the error? How accurate is this component? And how accurate is my Conrad Digital Multimeter for 14Mack 50?'

3) Dieter recommends first checking whether all the hoses are properly connected. There's a diagram (on page 60, for those who also have the book) that labels the hoses. And it turns out that the company that recently installed the ATM (see my previous post) seems to have swapped the red and blue hoses.

According to the manual and my girlfriend's Audi 80 (also a manual transmission, so the solenoid valve is in a different location), a black hose runs from the top (opposite the connector) to the air filter housing - in my case, to the intake hose behind the mass airflow sensor (MAF). At a 90-degree angle to that, also at the top, a blue hose runs to the pressure sensor of the boost control system, and a red hose runs from the bottom (next to the connector) to the turbocharger.

'In my case, the red hose went from the bottom to the pressure chamber, and the blue hose went from the top (horizontally) to the turbocharger. So, I swapped the two hoses, quickly sprayed some brake cleaner into the mass airflow sensor, and went for a test drive, expecting a significant increase in performance.'

He seems to be doing better, but I think that's more likely due to the cleaned mass airflow sensor (MAF), because the power loss at around 75-87 mph (120-140 km/h) remains the same. How are the hoses supposed to be connected to the solenoid valve?

4) The hoses were only secured to the valve with these clamps; they were just attached to the loader and the pressure sensor - I assume they work with vacuum, otherwise they would have probably flown off a long time ago, right? On the other hand, vacuum seems rather illogical in this context!

I am hoping (again) for competent help from the vast expanse of this amazing forum...

Greetings,

Jörch.

Hi,

Quote:

"00575 017 Intake manifold pressure control differential, intermittent fault" with the words "That means nothing, that's irrelevant, the car is fine now"?! Can the above-mentioned error message be related to the performance loss?

but 100 percent .
Since I don't have any practical experience with the 1Z model, I'll leave the hose-related issues to the owners of 1Z vehicles.
Just to clarify: as far as I know, the boost pressure control system in the 1Z engine operates with overpressure. Therefore, leaks in the hoses that are simply connected could be a source of problems.

Best regards, Rainer.

Hi Joerch,

Regarding the hose incident:
(Passat 35i 1Z B4, which is likely similar to your Audi 80...)

The solenoid valve is installed with the electrical connections facing downwards. The black hose connects from the top to the solenoid valve, the red hose goes out from the bottom, and the blue hose goes out to the side.

For me, the blue hose goes directly to the pressure sensor for the wastegate.

That means, just like you have it set up now, I have it set up the same way.

Best regards.
David.

Hi Rainer, Hi DocSnydor, Hi everyone!!

Thank you for your comments! During my long commute to work today, I immediately noticed that the turbo, with the hoses swapped, now delivers significantly more (or rather, now delivers the power it's supposed to) .

I'm going to buy some new hose clamps tomorrow and properly tighten all the hoses so that nothing leaks.

Does anyone else have any ideas about what might be causing my problem with the 'loss of power' at high RPMs under load, especially if addressing it doesn't improve the situation? Could a problem with the EGR valve produce similar symptoms?

How exactly does this solenoid valve work? It measures the pressure in the intake manifold and at the turbocharger – and then what? Does it redirect pressure from the turbocharger to the hose leading to the boost pressure control valve when a certain value is reached, or something like that?

This would mean that the valve, when idling, keeps the pressure sensor closed. As the engine speed increases, pressure losses due to leaks prevent the bypass from opening sufficiently, resulting in excessive boost pressure – hence the limp-home mode? Does the valve open gradually, or does it only have 'open' or 'closed' positions?

Greetings,

Jörch.

Hello,

Joerch wrote:

...Can a fault in the EGR valve produce similar symptoms?

No, and while driving, you would also have produced a significant amount of black smoke.
Does your engine smoke black just before the error occurs?

Quote:

How does this solenoid valve actually work? It measures the pressure in the intake manifold and at the turbocharger - and then what? Does it redirect pressure from the turbocharger to the hose leading to the boost pressure control valve when a certain value is reached, or something like that?

The control unit measures the boost pressure using a pressure sensor and controls the solenoid valve so that the target boost pressure is not exceeded.

Quote:

This would mean that the valve, when idling, keeps the pressure chamber closed. As the engine speed increases, pressure losses due to leaks prevent the bypass from opening sufficiently, which results in excessive boost pressure - hence the limp mode?

Okay, that's possible. Nevertheless, you should check the pressure vessel yourself, for example, using a bicycle pump.
The wastegate must not be stuck, and the pressure sensor must not leak.

Quote:

Does the valve open gradually, or are there only "On" or "Off" settings?

The engine control unit applies a pulsed voltage to the magnetic valve. By varying the duty cycle of this voltage, any desired position can be achieved.

Best regards, Rainer.

Hey Rainer!

Thank you for the information - one never stops learning... and somehow, I'm also one of those people who not only like to drive your car, but also want to understand it .

Occasionally, the driver of the car smokes, but otherwise, I haven't noticed anything else. Therefore, I will test the pressure sensor and properly connect the hoses to address the problem.

Are there any alternatives to the standard hose clamps? Cable ties probably wouldn't hold their tension for very long at the high temperatures near the turbo, but I haven't seen those small hose clamps with screws before either...

I will report...

Thank you and goodbye.

Jörch.

Hello,

Joerch wrote:

Are there actually alternatives to the standard hose clamps? Cable ties probably wouldn't hold tension for very long at the high temperatures near the turbo, but I haven't seen those small hose clamps with screws before either...

Flower wire without a plastic coating .
It might look cheap and poorly made, but it's free from Ma and it works.
However, plastic cable ties should also be sufficient, as the rubber hose won't be boiling anyway.

Best regards, Rainer.

The control unit measures the boost pressure using a pressure sensor and controls the solenoid valve so that the target boost pressure is not exceeded.


Where exactly does the control unit measure? Is this pressure sensor also located in the solenoid valve for turbocharger pressure regulation? It really shouldn't be, right? This pressure sensor could also be a potential source of error! Although: Would I generally have problems, meaning in all engine speed and load conditions?

Greetings,

Jörch.

Hello,

Flower wire without a plastic coating .
It might look cheap and poorly made, but it's free from Ma and it works.
Plastic cable ties should also be sufficient, after all, the rubber hose won't melt.

I didn't think about 'cold flow,' but rather about the 'yield strength' of the soft plastic of cable ties. However, the tensile stress on the cable tie might not be so high that it causes unwanted elongation. It's definitely worth a try.

By the way: What is 'Ma' - a specialized retailer for floral wire near you?

Hello,

Jörg.

Hello,

Joerch wrote:

Where exactly does the control unit measure? Is this pressure sensor also located in the solenoid valve for turbocharger pressure regulation? It really shouldn't be, right? This pressure sensor could then also be a potential source of error!?! Although: Would I generally have problems, meaning in all speed and load conditions?

I don't know where the sensor is located on your device, but usually it's permanently installed in the control unit and a hose runs to it (in which case you should check that hose for leaks and blockages), or, like in my engine, the sensor is directly in the intake manifold.
Theoretically, the sensor itself could also be a source of error, or its cables/solder connections to the control unit.

Quote:

By the way: What is "Ma" - a specialized retailer for floral wire near you??

*g*

Best regards, Rainer.

Hi everyone!

The problems just keep coming. Before attaching the clamps, I shortened the blue hose from the solenoid valve to the pressure sensor of the boost pressure limiter slightly, to have clean, tight ends. This put the hose under a little tension, and when the hose clamp was tightened, the connecting tube of the pressure sensor bent.

I don't know if the part was already damaged before, but now a new pressure sensor is definitely needed.

Since I'm in Cologne today and have some time, I ordered the spare parts (pressure sensor, new hose, and a new solenoid valve) from the local Audi dealer. I'd like to give a big compliment to the Audi Center in Cologne (Gerwigstr.) because they were very helpful.

Based on various part numbers, we were able to determine that the workshop that installed the automatic transmission in my car installed a motor from a '93 model into my '95 automatic car!!!

And that's despite the fact that I had specifically asked about it beforehand, due to the minor modifications that were made to the engine (different fuel injection system, different turbochargers)! When I inquired (unfortunately, only by phone), I was told that it was an engine from a 1994 Audi 80... of course, otherwise I wouldn't have given the order!

The magnetic valve for boost pressure limitation is definitely still from my 1995 engine, and the (now broken) pressure sensor is from the 1993 model. Furthermore, I read that the 1993 model still had a sensor for intake manifold pressure and one for intake manifold temperature, which were all removed starting with the 1994 model - I don't know how the corresponding values are now determined, or is that the boost pressure sensor that Rainer mentioned in his last post?!

'I'm now planning to buy the new pressure sensor that's compatible with the (93) turbocharger, but what should I do with the solenoid valve? The part numbers for the solenoid valves of both engines are different. My engine control unit probably belongs to the 95 engine; will I have a problem with a 93 solenoid valve because the signal is different?'

The error message from the last reading was 'Intake manifold pressure control difference' - where and how does the 95 engine actually measure the intake manifold pressure? Perhaps this control parameter no longer matches the engine control unit because it's being measured differently or in a different location!?!

By the way, I once disconnected and sealed the EGR valve just for testing purposes - it didn't make any difference to the problem of the engine switching to limp mode under full load and high RPMs...

'Anyway, I now have exactly the kind of patchwork repairs in my car that I didn't want... so I officially advise against having actions like engine modifications carried out by 'Autoverwertung Neumann' in Bottrop - supposedly a qualified workshop!'

Greetings,

Jörch.

Hi Joerch,

A quick question: How much does a pressure sensor cost for your Audi?

Sure, no problem.

David.

Hi David!

The workshop quoted me a price of approximately €270 for the parts, including the solenoid valve, pressure sensor, and hose. Based on the information I found on this forum, the solenoid valve costs around €30, which leaves approximately €240 for the sensor and hose.

Greetings,

Jörch.

Okay, thank you.

(They're really asking a lot of money for that pressure vessel, you could buy a whole car for that amount.)

Hi Joerch,
Are you from the Bottrop area? I'm from Bottrop.

Hi Joerch,
Do you come from the Bottrop area? I'm from Bottrop.

Hi Tim.

Currently, I live in Düsseldorf, but I'm actually from Essen.

Greetings,

Jörg.