The solution to the puzzle!!! 1Z power loss

Hello,

For those who don't know my 'story,' I'll briefly summarize it again:
'I have a 1Z engine with sluggish acceleration, as if the mass airflow sensor (MAF) is dirty or defective. However, the diode trick ruled that out. The boost pressure builds up about 500 RPM too late (0.9 bar only at 2500 RPM). I've already replaced the injectors, electronic stability program (ESP - although it previously had severe misfires), filter, and closed the EGR valve. I also cleaned the intake manifold. None of these actions have produced the desired results.'

Today, I found the cause: THE THERMOSTAT!!!

I've been driving this car for 3 years now, and it has approximately 90,000 km on the odometer. The water temperature gauge always hovered around 70°C, and the water only got warmer after some intense highway driving.
I didn't think much of it; it's probably a faulty sensor, or the needle is misaligned (I already converted my speedometer to blue/red lighting a while ago). Apparently, everything seemed to be fine, and the interior got nicely warm during the winter, etc.
Today, I finally managed to replace the thermostat (it's not a straightforward job on the 35i because you have to remove the power steering pump first...).
Look, the temperature gauge actually goes up to 90°C. The boost pressure is now about 0.9 bar at just under 2000 RPM. The engine sounds much smoother, fuel consumption has slightly decreased, and the acceleration is noticeably better. Well, a small cause (the thermostat cost me 15 euros) can have a big effect.
Apparently, I've been driving around with an engine that was too cold the whole time; hopefully, the wear and tear wasn't too high...
What I'm still wondering is: What does this actually have to do with boost pressure? Does the 1Z have a pre-heating function that runs until the full operating temperature is reached?

Best regards,
David.

hi doc!

Can you remember the thermostat thread from early spring? I already suspected that the thermostat had a problem back then!!!

But it's good that your vaporizer is working again!

DocSnydor wrote:

What I'm still wondering is: What does this actually have to do with the boost pressure? Does the 1Z have a pre-heating program that runs until the full operating temperature is reached???

Hi David,

That would be new to me, but that doesn't mean it's impossible...
If you want to know for sure, temporarily connect a 220 Ohm resistor in series with the temperature sensor, and then the EDC will again show an approximate water temperature of 70°C instead of 90°C .

Hi Doc!

I'm glad you finally found the cause!

You can probably guess what's coming next. We both experienced very similar symptoms, such as slow boost pressure build-up and the resulting loss of power. It would be great if I could get my heating oil-powered Ferrari running again in the same way.
However, I'm somewhat predisposed to be pessimistic, because I conducted another small measurement test yesterday, this time using a diode instead of a mass airflow sensor.
I could hardly notice any difference, except that the engine seemed to respond slightly better to the throttle in the lowest RPM range, somewhere between 900 and 1400 RPM.
Among other things, I also looked at measurement groups that included the coolant temperature. However, in those cases, the value was 86°C, not around 70°C like in your data, which makes this comparison probably invalid. It's a shame, really, because it would have been such a simple solution.

In the future, I will probably have to continue the search alone in order to unravel the mystery of the slow build-up of boost pressure.

Regards,
Alex.

Hmm, you said 70°C... but on my car, it also only shows '70°C'. My car only gets hotter when I'm stuck in traffic on the highway and it's warm outside. I had previously assumed that this was the normal operating temperature, but I'm also surprised by the relatively weak performance (around 180 km/h if I can drive perfectly straight for a very long time. I sometimes hear from others with 90 horsepower engines that they can achieve more...).

What's the easiest way to identify a thermostat malfunction? My car is going to ATU today anyway for the brakes, maybe they can fix that at the same time...


Regarding ATU: It might tempt me to also have ATU install a power box directly. What do you think about that? I can't say the brand, but it should provide +20 horsepower and +38 Nm of torque. My car is a Volkswagen Golf III, model 1Z, with 102,000 km on the odometer.

Hello,

The ATU-Powerbox is made by PSI. I have a similar chip installed in my Golf IV PD115 for 60,000 km, and I'm very happy with it. Of course, a different chip might offer even better performance, but I'm satisfied with what I have.

@misterx:
You can easily check the thermostat. It should only start to open the coolant flow just before reaching 90°C. If water is already flowing through the radiator before the engine has warmed up, then the thermostat is faulty.

Can you also determine this using a diagnostic system (e.g., VAG-COM)? The engine temperature is also displayed there. However, I don't know if ATU has a diagnostic system.

Either the temperature sensor (for the display) or the thermostat is broken. Otherwise, the display would show a temperature of more than 70°C.

Power boxes have been extensively discussed in this forum. Please check the 'General' section (/viewforum.php?f=10) under '10cent Tuning' (because that's exactly what a power box is), and also under 'Powerbox vs. 'Chip tuning'.

Regards,
Private.

WRONG!!!!!

This box has absolutely nothing to do with 10-cent tuning.

Take a look at the Cartronic homepage (the distributor of the PSI-Box) at dieselchip.de. There, the box, its functionality, and its structure are explained.

Thomas K. wrote:

WRONG !!!!! This box has absolutely nothing to do with 10-cent tuning. Take a look at the Cartronic homepage (the distributor of the PSI-Box) at dieselchip.de;

there, the box and its functionality and structure are explained.

Don't let those advertising guys pull the wool over your eyes.

External enclosures for VP37 are always designed based on the 10-cent principle!
Sometimes, only regulations based on the accelerator pedal position, boost pressure, or air mass are used to adjust the resistance at the right moment.

We've already discussed this before, some time ago.

Okay, I understand. Please provide the German text you want me to translate. I will only provide the English translation.

Hello!

I've now contacted my trusted mechanic to have them replace the thermostat (after all, what's the point of a used car warranty? *g*).

It would then cost me 30 euros instead of 140. However, I'm wondering if that's really the problem, because my Golf actually performs quite well up to about 150 km/h, but above 150 km/h, the acceleration is agonizingly slow. I'd like to test this, and I also have a VAG-COM and a laptop, and I know someone who is good at soldering and tinkering. The only problem is the connector on the car. Does anyone know where I could find one of these?


Regards,
MisterX

Hmm!

Please don't label me as stupid, but does the Golf III 1Z now have OBD-2, or what? Does it use a different protocol but the same connector? I would like to order a cable there, but which one do I need?

Hmm!

Please don't label me as stupid, but does the Golf III 1Z now have OBD-2, or what? Does it use a different protocol but the same connector? I would like to order a cable there, but which one do I need?

you asked about a plug or ???

'As far as I can tell, those cables are designed to work with their specific adapter, and that adapter is not compatible with VAG-COM. The adapter there is a dedicated OBD-2 adapter with a chip that handles the communication with the engine control units (ECUs). VAG-COM works in a slightly different way.'
Your Golf might not yet be OBD-2 compatible, but it probably has a socket where the connector fits! However, it's possible that you still have the 2x2 socket! You should check your Golf to be sure! You can also find information about the location of the diagnostic socket in the vehicle here in this forum! Please use the search function!

Okay, so I definitely have this wide connector with more than 2x2 pins.

Does this mean I can't use that cable with VAG-COM at all?

So, I definitely have this wide connector with more than 2x2 pins.

Does that mean I can't use that cable with VAG-COM at all?

That's what it means! The adapters listed in our technical articles should work with VAG-COM! And if you don't want to build one yourself, please contact Maik. He has built and tested these adapters before and shipped them.

@joergs

I still remember your tip about the thermostat (but so far, I've definitely lacked the motivation, because of the 60/40 suspension, no lift, and the power steering pump needs to be disconnected first...). Well, now I've finally overcome my inner laziness...

@Ulf

Oh no, you, I'm glad it's working. 'Never touch a running system'

@Alex
I will definitely follow up on this. I mean, my car is still not a rocket, but I don't even want to know how much that thing weighs...
Could it perhaps be related to the hydros in some way? Finally, the oil temperature was previously between 70-74°C, and now it's just below 100°C.

Hi!

I had the thermostat replaced today. On the first drive, I couldn't notice any increase in top speed (around 175 km/h on a straight section of the A31), but the temperature gauge now shows approximately 90°C (previous value: ~80°C). I also noticed that the turbo seems to respond better. I'll probably be able to say more tomorrow after my drive to work (Oberhausen to Cologne). However, I think 175 km/h is not normal. The car probably needs to be re-tuned. Is the thermostat on, and is the temperature now within the desired range?


Regards,
MisterX