1Z stutters

Hello,

My name is Daniel, and I live in the countryside with my family on a small farm. I have a lot of space to play here, and I've always enjoyed playing with my vehicles. These are all older cars from the VAG lineup.

Now, a beautiful T3 van with a 1Z engine conversion has arrived at our shop. I registered it, I'm customizing it piece by piece, and I'm slowly getting familiar with the modern technology and the initial problems. My most modern diesel engine so far, with a turbocharger, is the JX.

Okay, I'm experienced with mechanical and electrical systems, but I'm completely lost when it comes to electronics, although I'm definitely willing to learn. On the way back from my last trip, the engine started going into limp mode. Sometimes it would recover and run well. A restart didn't fix it. However, since it was running smoothly overall, the oil, water, and temperature were okay, and it was nighttime and raining, I drove the last 150 km home with this problem. It then sputtered a lot when I came to a stop. Since then, it only reluctantly catches a small amount of lift from a cloud, then performs a clean, round loop, and immediately shuts off again.

So, it was clear to me that I would now have to deal with the engine. So, I bought a VCDS diagnostic adapter in the blue case and downloaded the software. It seems to be working so far. The self-test recognizes the adapter and detects that the car is not connected. Unfortunately, it still says the same thing even when I connect it. So, the control unit is not being recognized.
Okay, I've checked everything for leaks and things like that, but I don't know how to check the electronics to see if the control unit is even working.
Oh, it had an open air filter installed, which I replaced with a closed system adapted to the original T3 system. However, even with the open air filter, it ran perfectly fine for over 500 km. I would really appreciate any help, even if it seems a bit clumsy in places.

I am a very analog person. Ah, yes, of course I checked the valve timing.

Best regards,
Daniel

Hello Daniel,

Welcome! Your most important items are:
- Check the timing belt pulley on the crankshaft of the 1Z to ensure it is securely fastened. This is a known weak point that has caused many 1Z engines to fail. If it is not secure, you could experience a complete engine failure immediately. Therefore, take this very seriously and check it carefully. Simply checking the timing is not enough. The frustrating thing is that, by chance, they might be roughly correct, but the ratchet is still not fixed.
"Does the timing belt sprocket show any signs of wear?" "The engine won't even start."
- Diagnosis from the engine control unit. This will tell you what kind of discomfort it's experiencing.

Quote:

Unfortunately, the same issue persists even when connecting it. So, the control unit is not being recognized.

So, is a diagnostic port (2x2 or 16-pin OBD) already installed? Which version? The pins in the 16-pin connectors sometimes slide backward and lose contact.
Regardless, please post a Screenshot of the VCDS interface test. When the ignition is on, the K-line is pulled to +12V by the engine control unit.
https://www.obd.wiki/k-line

The 1Z model came in various versions with different generations of fuel injection systems. The VAG part number on the engine control unit, or its Bosch number, is helpful because you can use it to search online and likely identify the donor vehicle.

If the 16-pin OBD connector is not present, you can order it online, connect the wires accordingly, and install it in a suitable location.
I would always choose this option; using a 2x2 configuration with an adapter introduces additional potential sources of error.

Best regards, Rainer.

Hello, I've tested the crankshaft pulley for strength.
Uploading images isn't working quite right yet.
Thank you very much and best regards.

Oh, it seems one thing actually worked out.

Hi,
T3 with 1Z engine conversion - what was the original engine? What year was it manufactured? And was the connection between MSG and 2X2 rewired?
hg
Herbert.

I would say that there was probably a JX engine in it before. However, I don't have any more specific information about that. The van is from 1986. I can't say what modifications were made to the engine control unit or the original wiring harness. I'm still in the early stages of my research and I'm quite inexperienced in this area.

https://www.obd.wiki/obd-2-buchse

Unfortunately, I can't clearly see in the picture where the gray and white cable connects to your OBD-2 port. Pin 7 is the correct one, as you can see in the image in my link, which shows the view of the OBD-2 connector when looking at it from the front.

Diagnosis can only be performed when the ignition is on. Then, using a multimeter, you should be able to measure the on-board voltage relative to ground.

I'll see if I can find the pin/wire color on the connector that goes to the engine control unit.

It should be pin 61.
Okay, I'm ready. Please provide the German text you want me to translate.

To-do list for you:
Connect the K-line from the engine control unit (pin 61, see details in the link in my previous post) to the correct pin on the OBD2 connector.
The three wires, which have been stripped of their insulation with heat shrink tubing, also appear to be heading towards the correct location on the engine control unit.

Since we don't know what modifications have been made, I suggest the following:
- If the K-line is connected to the OBD2 connector, determine which control unit (e.g., auxiliary heater) it is connected to. In this case, the K-line can be connected to pin 15 of the engine control unit (K2/L-line). The interface recognizes both.
- If the K-line connector is not available on the OBD2 port, connect the K-line to the engine control unit.

Hello, so the k2 l line is disconnected and yellow. However, it's not present in the tree. Also, there seems to be a missing ground connection, as there's something else nearby. I just found this corroded relay, part number 109, hanging loose behind the battery.

I just saw some cables running down from behind the battery, and there's an extra box attached under the battery that's not original. There must be something inside that box. I need to take care of my child now. I'll check it out later.

Relay 109 provides power to the engine control unit. Without voltage, the engine will not run, and diagnostics are also not possible.

Is the dashboard light connected to the engine control unit (ECU)? If so, does it turn on for a second when the ignition is turned on and then go out? (This would be an indication that the ECU is receiving power. Otherwise, you may need to measure the voltage directly at the ECU). While this isn't your original problem with the limp mode, it's possible that the engine has more than just the initial issue.

Hi,
A 1986 T3 with a JX engine doesn't have any original diagnostic capabilities; everything on the machine is mechanical. Perhaps there is/was an interface to the ABS control unit for flashing lights.
If a 1Z was retrofitted, an interface would need to be retrofitted in the same way. A 2x2 configuration would be the logical choice, although an OBD I/F might also work if the engine control unit (ECU) supports it. The existing wiring would need to be carefully checked and supplemented. "Finding another yellow cable won't solve anything."
Question: Is it an ESP system with a potentiometer in the setpoint device, or with an HDK sensor? The STG unit has a plastic housing that is identical to the MSA 12, and the part number matches that of a Golf 3 from 1994.
hg
Herbert.

Ronja_T3_1Z wrote:

Hello, I have checked the crankshaft pulley for strength. Uploading images isn't working quite right yet. Best regards

Question:
How did you check it? Several users have already commented that it's confirmed.
If the lower pulley is somehow warped or not running smoothly, then action is required!

Hello, first of all, thank you very much for the great suggestions and tips.

Unfortunately, I haven't had much time to properly look at it, and I won't be able to work on the van for the next two weeks. But I quickly measured something: the K line is definitely pin 61. That's all I've been able to do so far. There's still the box under the battery, and I need to measure the voltage at various points. But I won't have time for that again until in two weeks. I read something about an immobilizer. Maybe the control unit is hidden there, and there might be some problems with it. There's nothing quite like that in the original.

I tried to loosen the crankshaft bolt with 250 Nm in both directions, but it didn't budge. I wouldn't assume it's loose. I didn't want to loosen it, though, because it seemed to be holding securely.

I always planned to use the Jx. Are we similar in some ways, or what?

Best regards and thank you.
Daniel.

Hello, first of all, thank you again for all your help. Today, I finally had some time to work on the van. I figured out which pin is assigned to which function. So, relay 109 is defective and unfortunately, it can't be repaired by soldering. It looks like someone has already been working on it before. I ordered a new one.

I bypassed the relay, which finally gave me access to the control unit and the diagnostic tool. That's a good start. I took pictures of the error codes. Unfortunately, the car still won't start even after clearing the error messages. It sputters, then starts up erratically, revs cleanly once, and then dies again.


Best regards,

Hello, thank you for the feedback!

The altitude sensor is likely external in your case. You can see which pins of the engine control unit it's connected to by examining the wiring diagram.
/viewtopic.php?t=22938

With all these error messages, I suspect you have a problem with the wiring harness. Also, check if the height sensor is receiving its supply voltage when the ignition is on. Make sure the +5V isn't shorted anywhere.

Best regards, Rainer.