A8 4.2 TDI Exhaust Sooty After Injector Replacement

Hello everyone,

"At the beginning of the year, my A8 4.2 TDI (4H, 351 hp), which doesn't have a DPF, had a faulty high-pressure pump that released metal shavings..."

Everything has been fixed, replaced, and cleaned. I installed refurbished injectors from Dieselfixneus, but the engine ran terribly and kept going into limp mode.

Nozzles were installed and returned.

Due to time constraints and other circumstances, I bought a used engine from a local junkyard. It was apparently salvaged from a car that had been in an accident and had 60,000 km (approximately 37,000 miles) on it. The car has been running great with it (for about 10,000 km, or approximately 6,200 miles).

"However, I've noticed that the exhaust pipe and bumper on the passenger side now have a slight soot buildup. It seems there's something wrong with one of the injectors. Is there a way to detect the faulty injector without removing it? Otherwise, I'll remove all four and send them to a diesel service center. I have an original Audi diagnostic tool."

I would be grateful for any tips.

Regards,
Al.

Hi.

A diesel engine produces soot, and if there is no Diesel Particulate Filter (DPF), it is released through the exhaust pipe at the rear. Therefore, some soot residue is normal, especially if the exhaust pipe opening is visible beneath the bumper.

I wouldn't worry about it if everything else was running smoothly.

Quote:

However, what I've noticed is that on the passenger side, the exhaust pipe and the bumper now have a slight soot deposit.

Hello,

If the sides appear visibly different, I would investigate what is different on each cylinder bank.
Possible sources of unexpected soot include a leak in the exhaust system between the cylinder head and the turbocharger (which can be identified by soot traces). The turbocharger with the "leak" receives less drive energy, the boost pressure builds up more slowly, and the corresponding cylinder bank is then more prone to producing soot.
Another very common cause would be a leak in the charge air duct of the corresponding cylinder bank, such as a cracked charge air hose or a faulty intercooler.

I would like to compare the charge air control systems of the two cylinder banks, if each has its own measurement data. Also, if available, I'd like to see any differences in the air mass intake of the banks at full load. However, I don't know if and which measurement data are available for your engine.

Autoscan is always helpful.

Best regards, Rainer.

Rüdi wrote:

Hello. A diesel engine produces soot, and if there is no Diesel Particulate Filter (DPF), it is emitted from the exhaust pipe at the rear of the vehicle. Therefore, some soot residue is normal, especially if the exhaust pipe opening is visible beneath the bumper. I wouldn't worry if everything else is running smoothly.

Hi,

I've been driving the car for about 8 years. The exhaust pipes were spotless, almost like they were brand new. The blackening on one side only appeared after the accident. And as I mentioned, it's only on one side.

While driving, you don't see any black smoke, but after 1-2 tankfuls of fuel, you notice a slight soot buildup on the exhaust pipe and bumper.

The intercooler was actually leaking recently, but on the other hand...

Regards,
Al.

Is there anything stored in the error memory that could have a causal relationship with the soot formation?

Are the injectors unable to be programmed to the vehicle based on the entered number?