1Z stottert | Posts 16+

Hello,

The relay 109 arrived today and I installed it. With this, the power supply is normal, and I don't have any further errors besides the altitude sensor. I couldn't measure anything because the connector isn't populated, and there's an internal one.

Well, now that I can read error codes thanks to your help, I connected the other control unit that I have. This one doesn't show any errors, so consistently, there are no errors present. However, the car still starts briefly and cleanly after some cranking, revs up once, and then shuts off again. As I said, the second control unit doesn't report any errors. Perhaps I need to start looking at the mechanical aspects again.

Thank you all for now, it's really hot here.
Best regards,

Define "briefly increases".

Well, it starts up, then it fires, revs cleanly up to just over 3000 RPM, and then just dies. It's as if it's not getting enough fuel, then it briefly runs normally, and then it starts sputtering again because it's getting too little fuel.

3000 rpm is far too high for a "brief rev after starting." Is the engine control unit software original in both engine control units?

The fact that one STG is throwing errors while the other isn't also gives me pause.

Do you press the accelerator when starting the car?
The 1Z and subsequent models are electronically controlled, so you don't need to press the accelerator pedal (it won't make a difference anyway as long as the engine is below its idle speed).

If the engine revs up to 3,000 RPM without any pressure on the accelerator pedal, the first thing to do is figure out why that's happening. Not that he'll crank it up even more next time.
Is he revving the engine because he's burning his own oil? Or could the throttle valve on the fuel injection pump be misadjusted or blocked in some way, preventing it from reducing fuel flow?
These are the questions that need to be clarified.

And with each subsequent start attempt, I would always be ready to quickly shut it down in high gear.

The killer screw or a twisted timing belt pulley can only be reliably inspected by disassembling it and examining the wear pattern.

He seemed to start just by pressing the accelerator. I haven't consciously tried it without playing with the accelerator pedal yet. Unfortunately, I'm away for another two weeks and can't continue until then. Why isn't the marking on the clutch bell accurate? I have disconnected these components, which include the camshaft and diesel pump. Is there a difference compared to the JX model?
Best regards and thank you.

Could you please show me what the timing mark on the flywheel looks like and what the reference point on the transmission housing looks like? Please take a picture. Is the transmission also from the 1Z model?
By default, a "0" would be positioned on the flywheel, and would appear in the observation window directly in front of the edge. It would look like this: |0 , with no space. It might not necessarily be the case with a different transmission.
hg
Herbert.

Ronja_T3_1Z wrote:

It felt like it started just by pressing the gas pedal. I haven't consciously tried it without any play in the gas pedal yet. Unfortunately, I'm away for another 2 weeks and can't continue until then. Why isn't the marking on the clutch bell accurate? I have disconnected these components, which include the camshaft and diesel pump. Is there a difference compared to the JX model? Best regards and thanks

.
Hi,

No gas is needed for a TDI to start; it's only needed to keep it running if something is seriously wrong, either because the valve timing/injection timing is completely off, or because something other than diesel is being injected (e.g., air/foam in the lines instead of 100% diesel).

The startup process (simplified) works by determining a starting amount of coolant based on the coolant temperature, for example, 20mg/hour.
If the starter motor engages and the starting conditions are met (e.g., a minimum speed, although your ECU does not require a minimum speed for starting as long as it is compatible with a 1Z engine), the starting fuel quantity is injected.
The amount of fuel injected is continuously increased by the engine control unit, starting from a base amount, until an increase in engine speed is detected, indicating that the engine has started.

From that point on, the normal speed control system engages, and the idle speed is regulated. Even with very high injection amounts at the start time, the engine speed barely exceeds 1500 rpm, as it is immediately reduced.

So, if you're experiencing 3000 rpm, there are likely only a few causes, and most of them are not good.
- You're fiddling with the gas pedal. Don't do that; it's useless for the initial start. It's just as pointless as picking your nose; it has the same amount of impact.
- The accelerator pedal/cable is "faulty" and is sending incorrect values to the engine control unit. In such cases, the ECU shuts down the engine or switches to a low "limp-home" speed for safety reasons (I don't know the specific implementation in your ECU, but it will be one of those).
- An injector is injecting too much fuel (faulty), causing the engine speed to increase and the ECU to shut off the engine. However, it's unlikely that all four could be defective at the same time, which would explain the high RPM, but not the difficulty starting.
- The fuel injection pump's quantity control is misadjusted/defective. It's relatively easy to check the start and stop voltages of the quantity control device; there are technical articles available on this topic.
- Your ECU has some messed-up software installed. The presence of error codes that shouldn't be there, coupled with unexplained behavior, suggests this. I would take the ECU that's generating error codes and investigate the source of those errors.

I still suspect it's a combination of a loose timing belt sprocket and an ECU that's not compatible with the engine, possibly along with a corroded wiring harness.

I'm not sure if this has been checked already, but let's see if the ECU can be accessed via diagnostics while the vehicle is being towed (ensuring sufficient battery voltage -> using a charger), for example, by logging a data block. If that's not the case, she won't get any power, which could make it harder to start the engine because it won't be running properly.

Best regards, Rainer.