The car in question is an 1998 Opel Vectra 16XEL.
Recently, after doing some things on it:
- Replacing spark plugs
- Replacing ignition cables
- Oil change
- Replacing the gasket under valve cover
it developed the following symptom: the power on sub-3k rpm 2nd gear is basically non-exsitant. The other gears are fine.
What happens is when I go for example 20 kmph in 2nd gear (around 1,3k revs) and press the accelerator it just barely goes - I measured it once on an empty road and it took me 9 seconds to go from 20 to 40 kph. Quite frankly, 3rd gear 20-40 is faster.
After reaching 3k rpm it returns back to normal and feels like the power is back.
What could be the cause?
EDIT: I should probably add, when this is happening, the engine gives out a very low, bass sound and you can feel the car shaking. It all dissapears after the engine revved above 3k.