I have an Astra MK4 (G) with 120,000 km. Engine was overhauled around 90,000 km because of a faulty synch chain. I have had this car for 7 years, brand new assambled in germany.

The engine is not performing good. Mileage is contrasting, in sppedways, I can get 12Km/ltr, but in the city I can get 5-6Km/Ltr. Engine performance in general is not what it was in the past, is right now like 90-100hp in my perception.

Anyway, if I accelerate slowly, I can reach aroud 130Km/hr with 3,000 rpm. However, if I accelerate quickly, as the engine overpasses 3,500-4,500 rpm the engine looses power as if I wouldn't have enough fuel pressure. Regardless of the acceleration, If I press the accelerator all the way down, I get engine response so I can keep accelerating, but when I release the accelerator, the engine looses power and stumbles. During full power acceleration, gas consumption is bad like 4km/ltr.

Also I noticed that exaust tail gets full of coal, which suggest a too rich fuel/air mixture.

What I have done...

I changed the ECU because it had some pins damaged, also changed plugs, air and fuel filters as well. I changed CAT like 8 months ago.

I have a friend with another astra, same engine which runs great, so I had the chance to try different parts.

I exchanged, coil pack, acceleration body and MAP sensor with no change at all, same problem.

I have a tech2 scanner which is not registreing any DTC, also got an ELM scanner so I can register sensor data, but I have no way to compare or derive a problem from the data seen.

What else can I check or try?

Alfonso