VW AAZ: No Acceleration Below 1/3 Throttle

Hi, I'm not sure if I'm posting in the right subforum; the forum is a bit confusing for newcomers, but whatever.

Subject:
I bought a T3 with an AAZ engine, and it generally runs well, except for a problem with the fuel injection system.
It smokes a bit shortly after starting, but I think that will disappear with different injectors and glow plugs.
On the other hand, it doesn't accept any gas. When I pull the throttle lever, absolutely nothing happens in the first third of its range; only above that does it start to rev up.

The ESP engine is from an AAZ model, featuring a vertically mounted LDA (indirect injection) system and no electronic components. The intake manifold and turbocharger are from a JX model.

Regarding your first question, yes, that is the wrong category.

Well, what can you say? You're driving a fixer-upper. The crystal ball can tell us all the things that could be wrong with it. Unfortunately, mine is at home. There are certainly a few possible explanations for your description, starting with something as simple as a misaligned lever.

Is it really precisely checked which parts come from which engine?

Then, first check if anything is moving at all on the ESP in the 1/3 section.

Throttle lever not properly engaged.

First, understand.

Quote:

On the other hand, it doesn't accept any gas. When I pull the throttle lever, absolutely nothing happens in the first third, and above that, it starts to rev up.

Do you mean when it's idling?

hg
Herbert.

Yes, at idle.

The engine idles smoothly at approximately 1000 RPM. When I pull the lever or press the pedal, nothing changes; the RPM only increases after about a third of the travel.

My first thought was that the throttle lever might be misaligned, but all the reports I've read online say that the idle would be far too low in that case. I'll try moving the lever one notch further next week and see what happens.

I was just about to drive into the garage to check the ESP. I drove 10 km in city traffic without any problems. Then, at the town limit sign, I put it in 5th gear and floored it, but the engine didn't stall, which suggests the accelerator pedal is working.
"I'm in 5th gear, and it accelerates up to 90 km/h, but after 2 kilometers, it loses power and eventually stalls when I release the clutch."

"Initial attempts to start the engine have failed. The shut-off valve is malfunctioning, and fuel is visible in the hose leading to the ESP (Electronic Stability Program). Without tools and in the dark, there was nothing more that could be done."

Tomorrow, I'll check if the ESP is working properly by using a new fuel filter and fuel from the canister, and I'll also see if the fuel injection timing is still reasonably accurate.

Quote:

My first thought was that the throttle lever was misaligned, but all the reports online say that if that were the case, the idle would be much too low.

Warning: This is based on limited knowledge. As you can see in your picture, you most likely have a pump with a "non-removable idle spring" (or "integrated idle spring").
Nothing will happen to the LL if the lever is in the wrong position, unless it's in the reverse direction. In that case, the engine would rev up uncontrollably.

Actually, with that screw you're adjusting the residual amount, and that amount should be lower than the idle speed when properly adjusted.

If the timing is too advanced, your engine will behave like a carbureted engine that's drawing in unmetered air.

The two or three adjustment screws for the LL (likely referring to a specific parameter or setting) are located between the motor and the pump.
Attached at the front is the mechanical blocking device.

By the way, the thing is working again. It was due to the throttle linkage; it was installed correctly according to the markings, but it was off by one tooth. Now, the ESP is working as it should.

In addition, the tank was completely empty. It wouldn't start until I added 10 liters from canisters and hoses.

I hope you bled the fuel injection pump and didn't let it run dry?

hg
Herbert.

I only disconnected the lines to the ESD system, let the starter crank for 10 seconds, reconnected everything, and it started immediately. It seems that during the previous nighttime attempts, the pump had already filled the system, but not all the air had been bled from the high-pressure side.

"I've driven about 200km since then, and so far it's running well. However, when it's cold, it occasionally has some misfires with white puffs coming from the exhaust, but it seems to be happening less frequently. My theory is that the exhaust system isn't sealing properly, as the engine had been sitting for a long time. Also, either the boost pressure is set too high, or the blow-off valve is releasing too early, because it's definitely venting the boost pressure when you give it full throttle from a standstill."

Quote:

When running only on cold start, it occasionally has individual misfires with white puffs of smoke from the exhaust, but they seem to be decreasing

.

It probably stems from the fact that your ALFB (adjustable, load-dependent starting torque) is not connected - at least that's what it looks like in the picture, and the T3 model also doesn't have the control unit for it.

Connect a wire from the ELAB (electric shut-off valve) to the valve located at the bottom of the fuel injector adjuster (it looks the same from the outside), if there isn't already a wire connected there. You'll be surprised how much smoother it runs after a cold start.

Quote:

Furthermore, either the boost pressure is set too high, or the blow-off valve is releasing pressure too early; in any case, it's venting the boost pressure when you give it full throttle from a standstill.

Which loader is being used? Is it the one from the AAZ or the original one from the JX? Maybe take a picture if you're not sure.
It's possible that the wastegate is stuck, or that someone has already tampered with it.
Neither is healthy when the engine runs without an intercooler .

The turbocharger is from JX; I'll take it apart in the next few days because the exhaust manifold gasket is leaking. While I'm doing that, I can also check the wastegate.

I would have expected the injection timer to work the other way around, so that without power it would be set to an earlier time. I will try it out right away.

EDIT: Oh, this thing mechanically/hydraulically shifts to a late timing position under low load. When voltage is applied to the solenoid valve, the function is disabled. It might be possible to activate it when the KSB (Kurbelwellen-Synchronisierbremse - crankshaft synchronizer brake) is disengaged.

Quote:

I would have expected the function of the injection timer to be the opposite, meaning no power = early. I will try it out right away.

The valve is a reverse-acting ELAB (electromagnetic locking valve) or a normally open ELAB, as commonly found in marine engines.
If it's open, the feedback can be adjusted based on the load. If it's energized (closed), the feedback is only dependent on the speed.

The purpose is to achieve acceptable cold-running performance with relatively low CO and HC emissions, while simultaneously reducing NOx emissions during warm engine operation and low load conditions through a late fuel injection timing.

It actually runs much better with ALFB disabled; there are no more stutters or smoke.

During the operation, I noticed that the KSB (pressure switch) cable is bent, causing the motor to always run with the KSB partially engaged. When I manually push the KSB to its end position on the ESP (electric submersible pump), the motor runs poorly. I bet the pump start-up was adjusted with the KSB partially engaged, or even worse, not adjusted at all. Everything seems to be clarified now. I'll adjust the pump start-up and straighten the KSB cable in the next few days.