Knock fixes

[stx133]

i have a 94 540. when cruising at 100 kph, just under 2000rpm and attempting to gently incrrease speed or go over a slight hill, there is knocking / detonation sounds. this disappears when under 'low' load and also under full load.

i only run premium petrol but shouldn't the knock sensors cover that anyhow.

i do not think the ECU is aftermarket chipped but would this be a possible cause if it was. i neeed to find time to pull it out and check.

What are other possible causes?

Vacuume leak, sparkplugs....

[Ausmpower]

Maybe the drag of the fake M badge?

Low fuel pressure?

Farked O2 sensor?

Farked or not plugged in knock sensor?

Incorrect plugs?

Dodgey fuel (try Bp ultimate)?

Rooted big ends (noisey under partial load)?

Oil pump failing or bolts loose?

[Ross]

Vacuum leak most likely. Carbon build up perhaps but unlikely after seeing your sig. Don't ignore this!

[stx133]

seems to be heat related, it there temperature compensation on these things?
is ok on cool day, cool engine;. worse on hotter conditions.

[Ross]

It's running too lean! Check for unmetered air(vacuum leak).