Power Loss After 200km in Rain (ECU?)

Hello diesel mechanics,
My Golf III with a 90 horsepower TDI engine is now experiencing performance issues after 180,000 km.
Okay, here's the translation:

'I drove 200 km on the highway in extremely heavy rain. Everything was fine, no incidents. The next day, I started the car in the morning, immediately drove off, and the TDI engine felt like a half-power SDI. The maximum speed was probably only 60-70 km/h. Now here's the thing: If I rev the engine once while it's idling to over 3500 RPM before driving, it produces more power and drives around 120 km/h. However, if I turn the ignition off and on again, I have to rev it above 3500 RPM again, otherwise it only drives at those 60-70 km/h. If I give it gas while it's idling, the RPMs slowly increase to 3500 RPM, then they jump up to 4500 RPM as if nothing happened. Because of this, I took it to a VW dealer to have the error memory read.'
Okay, so what seems relatively harmless is the 00553 027: Air mass sensor - G70, implausible signal, occurring sporadically. It might be related to water from the recent rain. There's also some information about this here: /viewtopic.php?t=3687
Dann allerdings Saugrohrdruck Regeldifferenz 00575 017 sporadisch. Und wenn das nicht schon genug wäre 65535 000 Steuergerät defekt! TYes, what can we do?
First, I drove home. The measurement hose for the intake manifold pressure runs from the intake manifold to the engine control unit (ECU). I first disconnected it at the top of the ECU, and sure enough, when I gave it full throttle, water sprayed out. So, I removed the ECU, unsoldered the sensor, and: there was water inside. However, it was only in the sensor itself; the electronics of the ECU were completely dry. I tried to dry it, re-soldered it, and the problem persisted. Is the entire ECU really broken? Or should I just replace the lambda sensor first? But where does the 'ECU defective' message come from, and how can that be related to the rain? I'm looking forward to solutions! What kind of engineers were involved in designing this, that they integrate a sensor into such an expensive engine control unit?!
Greetings,
Chris.
PS: I've already searched the forum, but my problem seems more complex. All the hoses are leak-free, and the turbocharger is building boost correctly. The engine isn't producing any soot. The diesel filter is new, and the air filter is dry.

Hi,

The newer engines have the pressure sensor for the turbocharger located externally... someone clearly learned something from that. Also, the angle at which it's inserted into the pressure pipe from above should allow any water to drain out.

I would ignore that implausible LMM (mass airflow sensor) signal. It's likely a consequence of the fact that the plausibility check uses data like boost pressure, which is probably not being measured accurately in your case.

Regarding the sensor: I would thoroughly dry it (perhaps in the oven at 60 degrees - we had a discussion about that before), and then check it.

You should be able to find the datasheet with the pinout online. Then, connect a rubber tube and a syringe, and perform a plausibility check. If it's a Motorola sensor similar to the one I used for my LDA (www.uyna.de/auto/lda), it requires 5 volts and outputs a linear voltage of 0...4.5 volts corresponding to the absolute pressure.

If all of this is correct, then reassemble it and hope that it works again.

"I would initially ignore the 'engine control unit failure' message."

Then I would investigate *why* there's water in there, because it must have come through the hose, which is hardly possible because the air normally can't escape. Maybe there's a hairline crack?

Best regards,

Jan.

Hello Jan,
Thanks for your suggestions. The sensor is from Bosch. I bought an old gasoline engine control unit from a VW dealer, thinking the sensor might fit, but it's a Motorola one, and it's too big. I can't tell you the exact type right now; I'll have to take it out again.
I'm going to try using the oven. I'm also puzzled as to how the water could have risen so high. At first, I thought the hose might be leaking, but the water has actually reached the sensor. If there were no air leak, the water wouldn't have been able to get in...

Best regards,

Chris.

Hi,

Try using the syringe like this... If you apply some pressure (it takes quite a bit of force), you might be able to tell if there's a leak and air is escaping.

Alternatively, the membrane could be leaking, but if that's the case, the device is likely beyond repair.

I think there should also be a datasheet available from Bosch.

Best regards,

Jan.

Hello.

The Golf 3 has the control unit inconveniently located in a channel near the wiper linkage, between the arm supports. On the left and right sides of the car, inside, there are small holes, approximately 1 cm in diameter, located between the strut tower and the transition to the A-pillar. These holes allow water that accumulates in the channel to drain.
They can get clogged with leaves. This causes the control unit to be submerged in water. Over time, the connectors are not waterproof. This results in inaccurate readings. The engine won't start. Good luck getting it to work again after drying it out.

Tobias.